The trend of states reclaiming zoning authority from local jurisdictions marks a notable institutional shift. I trace this change back to the humble ADU, which catalyzed California’s statewide approach in 2016-2017. The concept is now spreading and evolving so rapidly that I predict the majority of states will implement preemptive statewide zoning measures to address housing issues—including ADUs—within the next year.

Why Statewide Reform Works

For local zoning reforms to succeed, several conditions must align: a pro-housing majority must be elected to city council, and planning staff must be committed to reversing decades of single-family-exclusive zoning. This combination is simply too difficult to achieve consistently, and I’ve concluded it’s unfair to expect local jurisdictions to shoulder this burden alone.

Even when political conditions favor housing reform, the policy implementation process requires enormous effort. Portland’s Residential Infill Project exemplifies this challenge—city staff devoted five years (2016-2021) and likely tens of thousands of hours to complete this crucial initiative.

Statewide reforms offer a stark contrast in efficiency, typically achieving policy changes within 0-2 years. Beyond speed, scale represents the fundamental advantage. Housing affordability operates as a regional issue, not a local one. Even if one city completely solved its housing crisis through innovative zoning and financing reforms, neighboring jurisdictions would remain unaffected, let alone addressing statewide housing shortages. In the absence of regional governments with statutory zoning authority, states represent the only viable mechanism for meaningful housing reform.

Observing Portland’s glacial zoning overhaul likely influenced Oregon state legislators to intervene through House Bill 2001 in 2019, efficiently extending similar “controversial” housing policies to cities across the state.

Analyzing Strong State ADU Reforms

Given the effectiveness of state-level ADU reforms, they deserve greater attention and analysis.

In partnership with the Mercatus Center, we have studied and cataloged the nation’s ten strong ADU zoning reforms, spanning Arizona, Arkansas, California, Colorado, Iowa, Maine, Massachusetts, Montana, Oregon, and Washington. Beyond this substantial number of states adopting strong reforms in the past year, intriguing variations have emerged within otherwise strong ADU legislation. These differences between states with strong reforms now capture my attention most—over time, we may systematically determine how specific zoning reform policy variations impact ADU adoption rates.

We excluded deeper policy analysis of the eight other states that have adopted only weak ADU reforms. Until primary barriers are addressed, meaningful ADU adoption remains unlikely, making further analysis of those states premature.

The Mercatus Center will publish our findings in September 2025. The paper’s essence can be understood through one comprehensive graphic, which is also available here as a high-resolution .pdf.

I was surprised to discover that Oregon, my home state, doesn’t compare favorably even against ADU reform newcomers like Arkansas, Iowa, and Montana. Come on, Oregon!

More seriously, fascinating policy fault lines have emerged, such as whether states have established dedicated statewide authorities to implement ADU reforms, and whether statutory authority supersedes homeowners association restrictions.

Moving forward, I’m eager to track these laws’ real-world outcomes. How many ADUs are actually being constructed as a result of these changes? Which detailed policies matter most for ADU production?

Come to think of it, we did not inquire about whether States are compelling jurisdictions to report their housing production metrics …we’ll have to add that one in next round.

I was elated when Massachusetts recently passed the The Affordable Homes Act, which includes an ADU provision (Section 8 of Chapter 150 of the Acts of 2024), that on its surface, is a strong ADU law, making it the 7th US state to adopt strong ADU laws. These states include:

1. California
2. Oregon
3. Washington
4. Colorado
5. Montana
6. Arizona
7. Massachusetts

However, upon analyzing the law in the context of Massachusetts’ byzantine framework of local regulations, it’s hard to really see their ADU regulations as strong. This post contains a letter that I have submitting the Executive Office of Housing and Livable Communities, the office that the law charges with developing regulations that embody the law.

In the draft regulations, Executive Office of Housing and Livable Communities has done a disservice by deferring to local ordinances on their dimenional standards–specifically their setback and lot coverage standards. Given how onerous these standards are, this deference to the local zoning will undermine the statutory intent.

My hope is that this office will read my letter, and letters like it from fellow ADU advocates, and update their rules to contain clear and objective standards that will apply to all jurisdictions in MA.

More broadly, as other States look at ADU reforms, it is clear that being cognizant of the relative restrictiveness of local dimensional standards is critical to the success of a given ADU law. In the case of MA, jurisdictional dimensional standards are so oppressive, that it will be very difficult for average homeowners to build ADUs, in spite of the strong statewide legislation.

Other states like Oregon do not suffer under such oppressive jurisdictional dimensional standards, so preemptive statewide setback standards are less critical. But, in states like CA and MA, it is in everyone’s interest for the state to lay down the law with specific details on what is and is not a “reasonable standard” for ADU development.

Without further ado, here’s my open letter to the Massachusetts Executive Office of Housing and Livable Communities on their ADU Draft Regulations. (*Incidentally, feedback is due by 1/10/25)

Public Testimony

Introduction

The Executive Office of Housing and Livable Communities (EOHLC) is not complying with Massachusetts’ new housing law, the Affordable Homes Act with its draft ADU regulations. The Affordable Homes Act states that 

 “No zoning ordinance or by-law shall prohibit, unreasonably restrict or require a special permit or other discretionary zoning approval for the use of land or structures for a single accessory dwelling unit, or the rental thereof, in a single-family residential zoning district; provided, that the use of land or structures for such accessory dwelling unit under this paragraph may be subject to reasonable regulations, including, but not limited to, 310 CMR 15.000 et seq., if applicable, site plan review, regulations concerning dimensional setbacks and the bulk and height of structures…The executive office of housing and livable communities may issue guidelines or promulgate regulations to administer this paragraph.”

If a local ordinance such as setbacks, lot coverage, or heights, entirely prevent the ability to actually build the promised 900 sq detached ADU, the “Protected Use ADU”, do those local regulations still stand? Under these draft EOHLC regulations, the answer is yes. 

By deferring to local ordinances in its draft rules, EOHLC’s is effectively adopting these local standards as their own. These local standards aren’t sufficient for the Protected Use ADU. Thus, the office charged with protecting ADUs, is actually preventing them. 

The draft EOHLC regulations as they are currently written, pay deference to existing municipal prohibitions on ADUs in their dimensional standards. 

The result of this deference is that ADU law will be ineffective at enabling homeowners to actually build ADUs in MA, rendering the law largely meaningless in many cases.

Instead, the state must set preemptive standards for Protected Use ADUs. 

Legal Foundations

The The Affordable Homes Act itself was written to allow people to build ADUs in Massachusetts as stated clearly and boldly in the regulation title “Regulation of Protected Use ADUs in Single-Family Residential Zoning Districts”. 

The EOHLC draft regulations themselves state, “71.01: Statement of Purpose (1) St. 2024, c. 150, s. 8 (the Act) amended M.G.L. c. 40A, s. 3 to encourage the production of accessory dwelling units throughout the Commonwealth with the goal of increasing the production of housing to address statewide, local, and individual housing needs for households of all income levels and at all stages of life.”

The deference to municipal dimensional standards is not in alignment with the spirit or stated purpose of the law (Section 8 of Chapter 150 of the Acts of 2024). 

Dimensional Standards

In particular, in the draft rules, EOHLCs regulators default to underlying zoning standards. EOHLC staff  did not consider that ADUs have entirely different dimensional needs than single family homes and that most MA jurisdictions do not differentiate these, nor do they have a sophisticated codes that recognize these nuances. Local zoning codes in MA disregard ADU geometry altogether, and EOHLC is exhibiting a misunderstanding of market feasibility for the development of ADUs by deferring to these standards. 

In this letter, I will illustrate how local regulations in MA are guaranteed to stop homeowners from building ADUs, throttling the ADU potential in Massachusetts by approximately 50%. 

In particular, smaller lots in older streetcar suburbs of Boston (i.e. inside of Rte 128) are where most ADUs would normally be built in MA due to infill pressures and inflated underlying land values in the Boston metro area. But, small lots can’t build ADUs under existing local dimensional standards in MA.  

Let’s now examine in granular detail how the local dimensional regulations related to lot coverage and setbacks completely undermine the ADU law. 

Most Local Dimensional Regulations in MA prevent ADUs

There’s hundreds of local regulations to critically examine, but we’ll arbitrarily pick on Billerica, although it would be just as easy to pick on Belmont or Carlisle or countless others. 

We’ll select a property and try to fit a 900 sq ft ADU on it (which the state law theoretically allows homeowners to build), based on local dimensional standards. 

Dimensional Standards in Billerica

 See page 115 of Billerica’s dimensional regulations for residential properties. 

• Side yard- 15 ft. 
• Rear yard- 20 ft. 
• Lot coverage- 25%   

1) Starting with lot coverage, on a 5,000 sq ft lot, if there’s already a 1,000 sq ft home, it would be impossible to add a 900 sq ft detached ADU or anything approaching it (25% of 5,000=1,250 sq ft. 1,250 sq ft-1,000 sq ft leaves only 250 sq ft for anything else). 

2) Let’s look at an actual sample property in Billerica. 

This lot is 7,405 sq ft. 

25% (lot coverage) of 7,405 sq ft = 1,851.25 sq ft of buildable area. 

1,851.25 sq ft of buildable area, minus the existing building 1,376 sq ft= 475.25 (1,376 sq ft is based on the interior square footage assessment from the county tax assessor- https://billerica.patriotproperties.com/Summary.asp?AccountNumber=4460)

3) 475.25 sq ft is not sufficient for even a 1 BR ADU. 

Based on this one lot coverage standard alone, these homeowners couldn’t build a decent accessible ADU for someone to age in place, let alone a couple to age in place. 

4) Next, let’s examine how incredibly restrictive these setbacks are for ADUs.  It would be geometrically impossible to build an ADU on this lot, or literally any of the adjacent lots in this neighborhood for that matter, using Billerica’s local setback standards. Not a single one of these lots shown here could build ADUs with a side yard setback of 15 ft and a rear yard setback of 20 ft (see image below).

How Rear and Side Setbacks Hinder ADUs 

To illustrate how large rear and side yard setbacks hinder ADUs, we’ll now switch gears from text and use diagrams instead. 

For the reasons described above, we will use a standard urban lot. This lot is 5,000 sq ft. It is 50 ft wide and 100 ft deep. 

We’ll position the typical primary house built on that typical property 20ft from the front street lot line, to comply with typical front yard setback requirements. 

Here’s an aerial image of six standard 50 ft by 100 ft lots with typical homes.

This first diagram below shows a typical lot, mirroring the massing of the six lots above. It shows front yard setbacks, the primary dwelling, and a 6 ft fire separation between the primary dwelling and the potential buildable area in the back yard. Notwithstanding setbacks, about 35% of the property is left in which to place a detached ADU in the backyard… somewhere.  

In these diagrams, each background grid box equals 10 ft. The diagrammatic property is shown as being 10 boxes long, and 5 boxes wide. 

Now, let’s show the potential buildable area once 5ft setbacks have been applied. This buildable area is fairly constrained, but there’s sufficient room to fit a good-sized one-story ADU in any number of possible configurations within the buildable area confines. 

Next, let’s show the potential buildable area of that same property if 10 ft setbacks were applied. We’ve suddenly shrunk the potential size of the ADU from over 1,000 sq ft in the diagram above, to only 570 sq ft (19 ft x 30 ft). 

As a point of reference, 570 sq ft is just barely large enough to accommodate a reasonable 1BR ADU. 

Next, let’s show the potential buildable area if 15 ft setbacks were applied. We’ve now shrunk the potential size of the ADU from 570 sq ft to 280 sq ft. 

ADUs of this size make very little economic or practical sense to develop. I’ve visited over one thousand ADUs in the last 15 years, and only seen three ADUs this size. 

Next, let’s show the potential buildable area if 20 ft setbacks were applied. We’ve now shrunk the potential size of the ADU to a maximum buildable area of 90 sq ft. Given that that minimum size bathroom is ~35 sq ft, this would leave approximately 55 sq ft for the living space. A queen bed would take up 33 sq ft. The kitchen counter with a fridge, stove, and sink would take up more than 20 sq ft. 

There wouldn’t be any space left to actually stand up in an ADU of this size. 

Legislation that Defaults to Underlying Setbacks

In the absence of designating prescriptive setbacks that preempt local zoning, legislation allows jurisdictions to use their existing setback requirements for ADUs. 

Cities that have given thought to ADUs may have crafted conducive setback requirements for them. However, municipalities often default to the “underlying zoning” standard when regulating side and rear setbacks for ADU on a property. The underlying zoning standards were originally intended to define the buildable area for the primary dwelling. 

Since there is ample space even on small lots for developing primary dwellings, it was likely never a challenge to “respect the setbacks”. 

The problem is that EOHLC defers to “underlying zoning” requirements for rear and side yard setbacks, which carry over to detached ADUs. And, the underlying setback requirements in MA are very onerous. 

• Westford, Massachusetts –   30 ft rear yard setbacks, and 15 feet side yard setbacks 
• Weston, Massachusetts –     20-45 ft rear yard setbacks
• Stow, Massachusetts  –        40 ft rear and side yard setbacks

These types of setback requirements are unfortunately not the exception; they are the rule. 

Indeed, most cities have  similarly onerous setbacks unless it has specifically viewed this matter through the ADU developer prism of “reasonable” regulations. 

Setback standards are legacy standards for primary homes established by planning staff, long before they ever considered the requisite geometry of building a detached ADU.

Current planners may have never given thought to how their zoning code is institutionally hindering the development of ADUs because they “rarely see ADU applications”. 

Connecting the dots? 

If a state claims to want ADUs as a policy matter to create more housing choice, it must institute “reasonable” setback standards for detached ADUs. 

The State should instead set reasonable, clear and objective standards for ADUs, and cities should have to comply with those standards. 

These EOHLC draft rules are insufficient, and are not offering clear and objective, nor reasonable standards for homeowners to build ADUs. Rather, these draft rules are perpetuating classist (and racist) regulations. 

Ironically, this draft says that cities should provide “Design Standards” that are “Clear, measurable and objective provisions of Zoning, or regulations, which are made applicable to the exterior design of, and use of materials for an ADU.”

EOHLC is passing the buck entirely by not doing this actual work itself, as the law is clearly intended to do. It has taken a lazy path, and deferred to all existing underlying zoning in municipalities.

 To be sure, municipalities (ie. planning staff & elected officials & housing obstructionists) will appreciate this EOHLC draft, of course, because it prolongs and empowers jurisdictions to entirely stop people from building more housing as they have successfully done for decades in MA  

But, this was not the intent of the law. 

If local regulations were sufficient to foster ADUs, there wouldn’t have been a need for a state ADU law. 

Many of the lots inside of Rte. 128, where approximately 30% of the population of MA lives (and where the affordable housing crisis is acute), will not be able to build ADUs, as a result of these deferential EOHLC regulations. 

Inder these local rules, many homeowners will be stymied and frustrated by dealing with the confusing text and codes, the restrictive morass of local zoning codes, “death by 1,000 papercuts”, after spending thousands of dollars paying architects, and will throw up their hands in frustration and forget the idea of building an ADU.  

In a liberalized ADU market, 2/3rds to 3/4ths of new ADUs are built as detached ADUs; this is what the market tends to create for a variety of reasons. 

Given that most ADUs are developed in higher-cost urban areas–central city neighborhoods- the lots that host ADUs tend to be smaller, largely established prior to automobile domination. Conversely, residential properties established in the mid and latter part of the 20th century tend to be larger lots on the suburban and exurban fringe of metropolitan areas.  

Based on the cities where ADUs are actually being developed in greater quantities, it is fair to assess that more ADUs are built on smaller urban lots (5,000 – 7000 sq ft) than on larger suburban lots (7,000 – 20,000 sq ft).

When establishing statewide laws that will impact the cities where ADUs will actually be built, it is important that the zoning laws are written such that it will actually allow detached ADUs to be developed in these places. If an ADU  law & its regulations do not help achieve that outcome, then they have missed the mark.  

Creating Clear Standards for ADUs

With all of that explanation provided, the answers are actually simple. 

A “Reasonable” Setback Requirement for Detached ADUs is 5 ft

In practice, most rear yard and side yard setback standards tend to be set in 5 ft increments: 5 ft, 10 ft, 15 ft, 20 ft, etc. And, of those, 5 ft setbacks is the only increment that actually allows for the development of detached ADUs. So, I’m throwing out there that moving forward for the ADUs, the best practice for ADUs are 5 ft rear and side yard setbacks. 

Lot coverage standards for ADUs are unenforceable 

And as far as lot coverage goes, the State has clearly stated that it wishes homeowners to be able to build 900 sq ft detached ADUs. EOHLC has an obligation to protect the rights of homeowners to build these 900 sq ft detached ADUs on their property. 

Thus, the State must set preemptive dimensional regulations that stipulate that any lot coverage standards that prevent the construction of a 900 sq ft detached ADUs are unenforceable. 

When we purchased our single family home in March 2020, the main downside was there was no obvious spot for an ADU. We are fans of having flexible living spaces and like the mission of denser living in Portland’s center. Our house is placed roughly in the middle of our 5,000 sq ft lot and while we could have technically squeezed an ADU in the backyard, it would’ve meant tearing up mature landscaping and losing play space for our kids. 

Four years later, we’ve ended up with a family compound and endless flexibility, but it was not the result of some brilliant mastermind plan. We kind of stumbled into this solution, learning as we went, and enabled by Portland’s increasingly flexible zoning rules. 

When we bought our house, we initially gave little notice to the 1940s side-by-side duplex rental property next door. We were occupied with the move and managing childcare during the pandemic. One thing that became abundantly clear over the ensuing months is that while we were lucky to have family in town, it would be more amazing to have family even closer…like right next door. Enter: the duplex. The duplex had a detached 2-car garage where we imagined putting the ADU we’d always wanted, just a few feet beyond our backyard property line. If only we could just buy that little garage! 

Our neighborhood’s zoning is R5, which meant bisecting the lot was impossible, but luckily the duplex owners were receptive to an off-market transaction for the whole place, and we closed on the property mid-2022. We started work on the ADU shortly after that, and completed our family compound vision in the spring of 2023.  

Here’s a bird’s eye view of how it turned out: 

We now have family occupying the ADU as well as one duplex unit. The other unit is a rental. 

In another convenient bit of luck, a hedge is what separated our property from the one next door, so it’s been simple to create flexible openings in the hedge to allow the kids to go back and forth between family members. 

ADU Building

The city of Portland’s Residential Infill Project now allows properties with duplexes to have ADUs, which is what made this whole thing possible. We built the ADU knowing we’d eventually condo-convert the whole property (more on that below), and wanted it to work as a standalone entity. This means it has its own utility connections. We are fans of a more traditional architectural style, which is more consistent with the early 1900s homes that dominate our neighborhood. Rather than matching the mid-century duplex, we designed the ADU to look like a little English cottage nestled between the neighboring buildings.

Our architect, Asmund Tweto, made sure the scale and orientation of the cottage suited the neighborhood. As a testament to his skill, people frequently ask how long ago we remodeled the cottage, assuming it’s always been there. They’re always shocked to learn it’s brand new construction. 

Stephen Hull was the builder on this project, and we were so pleased with his work. 

Total cost – $412k including

• Building: $367k
• Architecture & initial permitting: $28k 
• Landscaping & patios: $17k

We went with higher end finishes, European kitchen appliances, extra built-ins, and so on, because it was built for family members. One could save around 5-10% of the cost without all these customizations. Having separate utility connections for the ADU also added to the cost, around $10-15k. 

Timeline

• Started drafting plans: Nov 2021 (Note: our architect was working off plans he’d already created for my mom’s ADU previously, so we were able to save some money and time)
• Construction began: July 2022
• Completed: March 2023

The Condo Conversion Process

We ended up using the ADU and the north duplex unit for family members, and renting out the south unit. Once that unit is vacant our plan is to sell it, which we can do because we recently condo-converted the whole property. This will let us recoup the cost of building the ADU. 

Because we can’t divide the lot, the only way to sell one unit is to create a condo development. This process converts the duplex plus ADU into a three-unit condominium: the ADU, the north side duplex unit, and the south side duplex unit. 

It took 6 months for us, but our lawyer said it can sometimes take up to a year to complete. The process was pretty wild, and we fully had no clue what we were doing. Luckily, our attorney and paralegal (Karna and Deb at VF Law) were pros and led the charge very competently. Everyone living in the units is given legal notice and first right of refusal to purchase their units, and there are mandatory waiting periods which can make things drag out if you don’t have cooperative tenants.

Condo Conversion Cost – $26k including

• Legal fees: $16k
• Survey, reserve study, inspection, OREA and city fees: $10k

It’s not cheap, but the property is unquestionably more valuable when sold as 3 individual units rather than one whole compound, so we try to focus on the big picture. 

One complication is that we got a mortgage on the whole property when we first bought it, so once we start selling individual units we will need to pay off the mortgage and look into individual loans for the condos. I know developers who do this professionally typically sell all the units at once, which makes it a little smoother financially. 

This also requires a new insurance policy, since now we have to insure the HOA as well as the structures, while individual owners will insure the contents of their units. We wanted to keep HOA fees and bureaucracy minimal, so we put as many items as possible under the control of individual owners and just put the exterior structure of the duplex under management of the HOA. This let us keep monthly fees low: $204/month for each duplex unit and $54/month for the ADU. 

We look forward to sharing our ADU on the ADU tour and will be onsite to answer your questions about it! 

(You can jump to the Background on Colorado’s Legislation section below to get right to the new state law and predictions).

Me & ADUs in Denver Leading Up to Colorado’s Legislation

I was called many things during a dozen years on Denver’s City Council. I’ll own the label “houser,” because of my focus on affordability for low-income families. But “ADU advocate” wasn’t one of them.

I’ve known people who lived in ADUs: A young adult in a parent’s property here, a divorcing fellow-elected official there, and now friends managing their own as a rental to help afford their primary home. Yet twenty years ago, as a coalition organizer and equity advocate for a Denver community-based organization seeking to expand access to affordable housing for our lowest income neighbors, I never once thought about an ADU during my work.

In 2011 I was elected to serve as an At-large member of Denver’s City Council. I mostly went about my business as a serious affordable housing champion: creating housing funds, a decade-long journey on inclusionary housing, innovating on homelessness interventions and renter protections. A citywide rezoning in 2010 included standards for ADUs and the city saw a trickle of rezonings and permits in my early years.

I thought about ADUs during Monday night Council meetings. But they lived in the zoning hemisphere of my brain as one-off parcel rezonings. I never opposed them as a form of market-rate housing. I voted for every ADU rezoning I saw. But they didn’t excite me as an affordable housing strategy either.

Until two things changed: First, the pace of ADU rezonings increased, including entire neighborhoods exploring permission to build them. A 2019 comp plan update created clearer support for ADU rezonings citywide. That was followed by reforms to set backs, lot coverage, garage conversion and other barriers that just passed in 2023.

The 2019 Blueprint Denver Plan and its language supporting ADUs.

The map below shows the current status of ADU zoning in the city. All but a third of Denver’s residential areas allow them. The process to expand ADUs zoning to those remaining areas, which will ensure Denver conforms with the new state law, began even before its passage.

From Denver Community Planning and Development presentation to Denver City Council, March 18, 2024.

Second, our public Denver Housing Authority took on a pilot to help low- and moderate-income families build affordable ADUs in heavily Latino and lower-income West Denver communities. The neuropathways between the affordable and zoning hemispheres of my brain formed.

Affordability and equity outcomes from the West Denver Single Family + ADU Pilot Program.

I was all-in for the West Denver Single Family + program (WDSF+), as the pilot came to be known, with its subsidies and rent limits. But with no data at all, at least from our local market, I was skeptical market ADUs would serve households struggling with affordability in my city, one of the most expensive housing markets in the nation when accounting for incomes. In fact, because building ADUs was (and is) expensive, many Denver ADU owners rent them short-term to help cover their loans, an anathema to long-term affordability.

When our governor Jared Polis began hinting at major land use reform to require ADUs statewide in late 2022, most of my peers in local government were opposed on the grounds of local control. I was intrigued.

I waited for the big case-making studies common before big legislation. I’d keep waiting until I decided to write that paper myself earlier this year. Before I did, not a lick of statewide data was available on what we in local government had already passed, who it was serving, the prospects we could expect from a statewide change. I had to dig for myself to learn the prices ADUs were renting for, and to whom, in other ADU reform communities or states. Regular Coloradans had access to no information at all beyond broad rallying cries that ADUs were “affordable housing.”

My full-length paper from May 2024.

Attempts to pass land use reform without showing communities how changes promote affordability, and without actual affordability components to serve even lower-income families, undermines the potential for widespread public support of those reforms. Less public support translated to less political support, first to pass ADU and other reforms at the state capitol (until lessons were learned and affordability funding was paired in a successful 2024 attempt). But more importantly, without broad support it’s harder sustain and implement ADU reform in the actual communities where they are built. I was awarded a Colorado Bell Policy Center Economic Mobility Fellowship to research the evidence and then to broaden understanding for when and how land use reforms like ADUs hold promise for greater affordability. The newspaper column below and this radio interview are examples of sharing the narrative with wider, public audiences.

I was a tough customer. But the evidence makes the case for the potential of ADUs: for some moderate income households on their own, and for more low- and moderate-income households with extra efforts and funding.

Denver Post Perspective Section cover of April 28, 2024.

Background on Colorado’s New ADU Legislation

Colorado’s first omnibus land use reform bill that included state-wide zoning reform for ADUs, SB23-213, crashed and burned at the close of our 2023 General Assembly. But legislative sponsors learned from their mistakes, and land use reform was reborn in 2024 with a package of separate bills. Most included funding for actual regulated affordability or menus requiring local governments to employ affordability strategies, or both.

HB24-1152 was the 2024 bill dedicated to legalizing ADUs in Colorado’s urban areas. It covers about 64 local governments (within metropolitan planning areas) and represents 65 percent of the single-family homes in the state. It comes with a voluntary opt-in path for the remaining rural and resort communities, $8 million dedicated to local government fee reductions, toolkits etc. and $5 million for low- and moderate-income homeowner subsidies. It passed in the final days of the 2024 Colorado General Assembly, incorporating many of the best practices proven to increase ADU production elsewhere, but with a few tweaks to get it over the finish line:

• By-right zoning for units between 500-750 sq feet
• Setbacks can’t exceed those for the primary dwellings (or 5 feet in the back)
• Minimum lot sizes can’t exceed those for primary dwellings
• Allows requiring a single parking spot only where no on-street parking is available and an existing requirement was in place as of January 2024
• Owner occupancy can only be allowed at the time of permitting, a first-of-its-kind compromise intended for those who want to try to deter investor speculation while ensuring no owner will be stuck with a primary home/ADU they cannot rent if their circumstances or the economy changes after permitting or construction

Communities are required to conform with these requirements by June 30, 2025.

What Will Happen Next with ADUs in Colorado

Litigation

You know that part in the wedding where the officiant asks if anyone objects? Well, local objectors didn’t have a vote before Colorado’s ADU vows were sealed by their state counterparts. But there is almost certain to be a legal challenge to attempt to annul implementation before that June 30, 2025 deadline. Colorado Municipal League is likely to line up and support a couple of its municipal members as litigants. Colorado is known for strong home rule protections, and land use is historically a local domain (the State of Colorado doesn’t even have a planning office). The challenge will not be frivolous. But the Governor’s team has clearly been preparing for more than two years, so arguments to meet Colorado’s legal test for proving the state’s interest in uniformity, and on the negative impacts of zoning restrictions on residents outside a single community’s boundaries, are surely well-developed. Stay tuned. The remainder of this analysis assumes no injunction issues and that the law survives challenge.

Pre-Implementation Production Will Continue to Rise Due to Local Momentum

My paper, Can ADUs Deliver on the Promise of Affordability for Colorado? includes the first-ever baseline data on ADU permitting in the largest 32 of the 64ish local communities required to allow ADUs under the new law.

Across the 13 jurisdictions with broad ADU zoning and available permitting data, ADUs are being permitted at an average estimated rate of 0.6 per 1000 single family homes per year.

Excerpt of table of Colorado ADU zoning and permitting from my full length paper, which was created before the legislation was finalized. For a more accurate list of the jurisdictions covered under the final version of the bill, see the table at the bottom of this post.

Permitting was already on an upward trajectory in these cities even before the state bill passed. Several other cities had plans to take on ADU zoning at the time the state legislation passed. It takes many months to plan, finance, permit and then build an ADU. Therefore, any rise in permitting over the next 12 to 18 months will mostly be attributable to the local ordinances and efforts already in place or underway and not to the new requirements in the state law. Though increased awareness as a result of the state debate could boost homeowner interest.

Interest rates and inflationary pressures on construction pricing have made ADUs more expensive to build in the past several years. Until rates drop, they’ll continue to put downward pressure on the ADU potential that already exists, and perhaps even future potential if these economic forces persist after the state law is implemented. But Colorado’s on-going housing crisis has bred ADU momentum that seems to be outpacing inflationary cost pressures for families with means to pay the premium. At least at the permitting phase, as evidenced by activity over the past 24 months in the 13 jurisdictions I examined. Permitting and completing construction of an ADU are two different things, however.

Anecdotal evidence from the few communities with reliable data on completions indicates a rate of abandoned projects, or in cities like Denver where permits don’t expire, possibly extended delays. Twenty-seven percent of Denver ADU permits pulled since 2018 weren’t built or are still pending according to WDSF+. The program hears that surprise costs or escalation after permitting underly many of those stalled or abandoned ADUs. The state legislation did not take on what many argue are inequitable and overly burdensome infrastructure fees, for example (sewer connection, requiring pre-existing sidewalks to be brought up to code etc). With state legislation in the rear view mirror, homeowners and their ADU advocates will likely elevate concerns about cost and financing moving forward.

The state’s new $13 million in homeowner subsidies and local government grants will be an incentive for pro-ADU communities to come into compliance faster to access the money. A local government must meet the state standards and be designated as an “accessory dwelling unit supportive jurisdiction” to be eligible for local government grants or homeowner subsidies administered through the state. The jurisdictions most likely to see the quickest bumps in permitting under this scenario would be those whose zoning and regulatory systems need only minor adjustments.

If these local governments act quickly, and if the state is ready to actually certify them and disburse funds before the statutory deadline, it could provide a permitting boost or improve completion rates for the current and near-term pipeline of homeowners already working to design or finance ADUs–even before zoning implementation fully takes hold statewide and attracts a new generation of ADU aspirants.

Post-Implementation Production Will Rise Slowly in Communities New to ADUs, Faster in Those Making Only Tweaks to Existing ADU Laws

For the vast majority of jurisdictions that have no or overly restrictive ADU zoning today, implementation of the state guidelines is their first step, or hurdle. Some will relish the opening, helping them overcome vocal but perhaps not overwhelming opposition. Others will be opposed themselves, or face or fear backlash resulting in resistance. There are no explicit or unique penalties for missing the deadline written into the legislation, though the state has insisted it will have the legal power to compel compliance. My bets are on a slow and cautious approach to doing so. The ADU bill is only one of several land use reforms to pass this year, and the state will be reluctant to pick high profile battles before trying collaboration over long lead times. 

Assuming a best-case scenario of using the next year to pass a conforming ordinance by the deadline, then a year or two to get the review and permitting systems running smoothly and to build interest among homeowners, who also need time to design and get financing: it will be 2+ years before many permits issue under first-time ordinances directly attributable to the state legislation. Expect 3-5 years to see many of those ADUs built and occupied.   

Again, however, the effects of state reform should be felt more quickly as the causal factor increasing permit rates faster than they would have risen otherwise in cities already building ADUs. Conformance for these cities will mean dropping parking requirements for most (if they use use the narrow state exceptions) or all parcels, and removing long-term occupancy requirements. Both the largest city in the state, Denver, and the top ADU-producing community statewide, Boulder will have to undo long-term occupancy requirements and Boulder will also have to eliminate parking requirements. If changes take place by the one-year deadline in these and other cities already building ADUs, permits could begin rising immediately upon local ordinance passage/at the start of year two, as some homeowners will begin planning now and wait to take advantage of the new standards.

If Colorado were to achieve 3 ADUs per 1,000 single family homes throughout all the areas subject to the new state requirements (a baseline based on a recent average permitting rate across the state of California), it would represent 3,300 ADUs/year.

But How Will We know?

Missing from Colorado’s new law is a data collection or reporting provision, aside from those receiving grants, to ensure the public can efficiently monitor ADU production post-passage across all the covered jurisdictions. It was likely omitted to minimize burdens and soften opposition from local governments.

As I can attest, collecting this data city-by-city is a mean task. And as evidenced by the lack of third-party research before introduction and my own, Colorado lacks a home-grown, well-funded academic research center or think tank focused on affordability and/or land use likely to do so with any regularity (think the UC Berkeley Terner Center in California or the NYU Furman Center in New York).

If Colorado’s law survives challenge, I predict a future effort to amend the bill for more reporting. In my paper I comment that the marginal burden of reporting is nominal in comparison to the underlying zoning and regulatory reforms themselves, and it could be phased-in, starting with larger jurisdictions with more staff first.

What Will the People Say?

The ADU bill had one Republican co-sponsor but was opposed by most others in that party; its passage was made possible by a (not-quite unanimous, but close) Democratic trifecta controlling both chambers and the Governorship. Governor Jared Polis and legislative sponsors were well armed with favorable polling on a generic state-wide ADU requirement going into the 2024 session.

January 2024 poll by Keating Research from Centennial State Prosperity.

The Governor is not up for re-election and will be termed out in 2026. Because Colorado has turned overwhelmingly blue, only a handful of legislative seats will be seriously contested in the general election. Passage of this year’s historic package of land use bills alongside renter protections gives the majority a strong record to demonstrate action on housing affordability, but the races won’t be competitive enough to tell us what voters really think about ADU implementation at home in their local neighborhoods. Those of us who’ve been around the block understand that overwhelming poll support for high-level affordable housing solutions can erode quickly when change comes to residents’ blocks.

That said, regardless of whether legislators need case-making to win state races, proponents would be well-served by broad and sustained communication efforts to break down the explanation for why and how ADUs can expand affordability. This includes talking about the specific incomes likely to be served by market-rate homes and who is struggling in those brackets (my analysis points to 80% of AMI renters).  And touting the paired funding already coming along with opportunities to identify more, to replicate models like WDSF+ to serve more low- and moderate-income homeowners in more communities across Colorado.

We also, all, need to talk a lot more about attached ADUs, aka basement conversions. They are cheaper to build and can blend into communities more easily than detached models, especially those with more suburban block forms, no alleys. And no one uses pictures of them or talks about them when broadly promoting ADUs. (Unfortunately, to maintain uniform and easily replicable pre-approved designs, the WDSF+ pilot doesn’t support attached ADUs).

In my 12 years in elected office I’ve seen 5 colleagues defeated in elections that turned on anti-growth/anti-development sentiments. Three of the communities now governed by this ADU legislation passed growth limits at the ballot box (now preempted under 2023 legislation). If state leaders expect ADU legislation to succeed, they need to follow zoning legislation with not just technical assistance, but communications and political support for local elected officials on the front lines. And funding will have to keep flowing to help low- and moderate-income Coloradans actually build them to meaningfully deliver on the promise of affordability.

Colorado’s ADU marriage can be a happy one, but like all relationships, it will take hard work that only begins once the honeymoon celebrating the passage of our first bill is over.

~

If you’d like to read more of my analysis of Colorado land use, affordable housing, other equity and political issues you can follow me at Robin Kniech’s New Take on Substack.

This blog post was revised at 7:11 pm on 7/10/24 to correct typos in the bill number, and to update the total number of jurisdictions and percentage of the state covered by the final version of Colorado’s ADU law HB24-1152 signed into law and to add the table of covered jurisdictions below.

First, the awesome news: Both Arizona and Hawaii have adopted statewide ADU reforms in the last two weeks. 

The accelerated pace at which these statewide reforms are enabling the development of ADUs, is incredible. Almost overnight, millions of homeowners in AZ and HI will be able to help solve the housing crisis for their community, and simultaneously solve their own housing needs.

Statewide ADU reforms are the hottest trend this year in housing laws. 

Here’s a summary of what Arizona’s laws do. 

Arizona’s HB 2720

• Allows an ADU in cities with a population of 75K or greater. 
• For each ADU that is designated as “restricted-affordable dwelling unit”, either through a deed restriction or a development agreement with the municipality, rented or sold to households making up to 80% of the area’s median income, the owner can build an additional ADU. 
• Drops owner occupancy requirements for ADUs
• Drops parking requirements 
• Cities may not impose rear or side setbacks greater than five feet from the side and rear property lines.
• ADUs may be up to 75% of the floor area of primary house or 1,000 sq ft, whichever is less
• No requirements for design matching of primary home, or any development standards more restrictive than for other single dwellings in the same zoning area
• Arizona will defer to restrictive covenants concerning ADUs entered into between private parties. 
• If municipalities do not adopt these regulations by January 1, 2025, ADUs will be permitted by default.

With the passage of this law, Arizona has made it to the elite cohort of states with strong ADU codes. Welcome to the ADU club, Arizona! 

The only major flaw with this bill is that it’s limited to cities of 75K or greater, which include the following cities.   

1. Phoenix (1,609,456)
2. Tucson (541,033)
3. Mesa (503,390)
4. Chandler (275,618)
5. Gilbert (267,267)
6. Glendale (248,083)
7. Scottsdale (240,537)
8. Peoria (191,292)
9. Tempe (181,005)
10. Surprise (145,591)
11. Goodyear (97,542)
12. Yuma (96,314)
13. Buckeye (95,042)
14. Avondale (89,214)
15. Flagstaff (76,177)

This 75K population threshold provision excludes 36% of the population of Arizona. I’d be so frustrated if I lived in a smaller town in Arizona like Prescott, Sedona, Bisbee, and was still subject to byzantine ADU rules because my city had fewer than 75K people in it.

ADUs without a kitchen are not ADUs

An oddity of the Arizona legislation is that it says explicitly that ADUs do not have to have kitchens. More precisely, it states that a municipality may not: “Require kitchen facilities in an accessory dwelling unit.”

It’s good to make codes as flexible as possible. But, it’s also good to keep things straightforward. And, this little quirk in the legislation definition of ADUs probably does not do any favors for amateur homeowner developers. I’ll explain.  

1. An ADU without a kitchen is actually not an ADU. Rather, ADU without a kitchen is called an “accessory structure”, or “detached living space”. Accessory structures are a real thing. They’re all over the place. You may have one on your property in the form of a garage, a shed, or a detached backyard office, or a detached bedroom. They’re actually legal in most places, and they are a great loophole to know about when codes otherwise preclude the development of “ADUs”. But, it’s incorrect to call an “accessory structure” or “detached living space” without a kitchen an “ADU”. 

2. This misappropriation of terminology is going to cause problems in fringe cases, because Arizona’s official ADU law now collides with the stated definitions used by GSE financing agencies such as Fannie Mae, Freddie Mac, and FHA. 

If a homeowner chooses to build an ‘Arizona-special ADU’ without a kitchen, their lender and appraiser may not agree that they’ve actually built an ADU, and may not wish to value the property as such. And, their lender would be correct! 

This kitchenless ADU would not rise to the occasion of being a “single family home with an ADU” in the eyes of most lenders, since it doesn’t conform to GSE standards for an ADU, and this will ultimately cause financial hardship for the homeowner when they attempt to refinance or sell the property. The homeowners won’t be able to get appraisals or find comps easily, and a future buyer won’t be able to obtain financing for the property as easily. 

The Fannie Mae definition of an ADU necessarily requires that it have ‘space for cooking’. ie. It MUST have a kitchen to be an ADU. 

3. Ultimately, this quirk is probably not really a large-scale flaw in the law. It’s only going to cause unnecessary confusion. And, as I mentioned earlier, it does provide more flexibility to an owner who really does not want a kitchen in their accessory structure for some reason. But, ADUs are a confusing and complicated topic already, and this perversion of ADU terminology will confuse lay people.

The distortion of ADU terminology is a trend that was launched in force via California’s statewide ADU legislation with “Junior ADUs” and “Bonus ADUs” and “Multifamily ADUs” and also jurisdictions classifying ‘tiny houses on wheels’ as a type of ADU. 

Distorting standardized terminology causes market confusion, especially in areas of the country that don’t have have many legal ADUs yet. My hope here is that States and jurisdictions would try to use standard terminology, rather than dilute the precision of the English language by calling more and more types of housing “ADUs” because it’s politically expedient. 

Alas, I continually lose linguistic, perfectionist pet-peeve battles like this one, and it’s probably better for my sanity if I simply let this issue slide. The important thing is that we allow more people to create more infill housing. 

…But, I still like to gripe about it. 

Hawaii’s ADU legislation – https://legiscan.com/HI/text/HB1630/2024 

Hawaii has also signed ADU legislation into law on May 28th, 2024. 

This bill requires cities to allow two ADUs and drops owner occupancy requirements. 

However, this law leaves the bulk of the ADU development regulations up to individual jurisdictions, such as off-street parking requirements, setback requirements, and size limits. Thus, I would not place Hawaii’s ADU legislation in the strong ADU legislation camp. It’s tepid ADU legislation that does not ensure that homeowners are allowed to build ADUs by right in practice. 

Here’s the hour-long press conference that announced the new ADU law. At minute 31 of the presser, there was a great back and forth that I wanted to highlight. The question posed was from KITV. “Critics are saying this would make the neighborhoods more crowded, increase profits for developers, and create you know, other issues. Can you address that?”

Hawaii’s Governor Green stepped up to the mic, and joked, “The Senator has a particular rage for this type of NIMBYism”, and beckoned US Senator Brian Schatz, who was in attendance, up to the mic. 

Senator Schatz reflected and then launched into a surprisingly insightful narrative about how restrictive ordinances for ADUs are unintentionally carrying the torch that was first lit by Jim Crow laws.  

“Look, we need more housing and we have to understand that when the Supreme Court outlawed Jim Crow segregation, that organizations wanted to continue to segregation, sat down with the then National Association of Realtors, and came up with restrictive covenants, minimum lot size, and they had specific language that they used protecting neighborhood character, protecting community integrity. 

And, even this year as this bill as this bill was being contemplated, individual legislators said that this was cause slums and violence and disease. Vectors for disease. 

And, we need to understand that that language is rooted in post Jim Crow America. 

And so those of us who are steeped in the Democratic Party’s traditions need to understand that when we oppose housing on the basis of neighborhood character, when we oppose housing on the basis that densification would cause disease, we are really the great, great grandchildren of Jim Crow. 

So, there needs to be a reckoning among Hawaii progressives about what it means to be progressive if you are for the nurse having housing,  if you are for the elderly having housing,  if you are for the disabled having housing, if you are for the UH or HBU students having housing, that housing has to go somewhere. 

And, some things matter more than the aesthetics of your neighborhood.”

Dang, Senator Schatz, I’m not Hawaiian, but I’ll totally vote for you. 

Despite Schatz’s bold statements addressing the common restrictive ordinances that housing development faces, Hawaii’s ADU bill does not actually addressing a number of the very common poison pill barriers to ADUs that he called out in his elegant disposition, such as off-street parking requirements, or minimum lot sizes. 

Before we say Aloha to Ohanas, I’ll mention that there’s an ADU financing bill in the works, but it has not yet passed. 

Some observations about current statewide ADU reform trends:

Two ADUs

These two bills in Arizona and Hawaii both allow two ADUs, similar to Washington and California. Washington’s policy is the most liberal and explicit of these, and therefore it has the best legislation of those four states for in terms of allowing two ADUs. 

Middle Housing Reforms Passed Simultaneously 

Arizona simultaneously passed a middle housing bill (HB 2721) when it passed its ADU bill. Like Washington, Oregon, and Colorado, the legislation simultaneously passed strong ADU reforms and strong middle housing bills. There’s a lot to say about these matters, but in order to keep this article more focused, I’m not going to stray too far down the middle housing road.

To Defer or Not to Defer to HOAs

There’s two different camps for how to contend with HOAs and ADUs. One approach defers to existing covenants commonly found in HOAs, and one that supersedes all existing covenants. Here’s examples of each: 

(b)  This section shall not apply to any private covenants recorded before the effective date of this Act.

From Hawaii’s new ADU law. 

4751. (a) Any covenant, restriction, or condition contained in any deed, contract, security instrument, or other instrument affecting the transfer or sale of any interest in a planned development, and any provision of a governing document, that either effectively prohibits or unreasonably restricts the construction or use of an accessory dwelling unit or junior accessory dwelling unit on a lot zoned for single-family residential use that meets the requirements of Section 65852.2 or 65852.22 of the Government Code, is void and unenforceable.

From one of CA’s 2019 ADU law

There are two distinctive legal approaches at play here, so it’s worth noting: 

One approach says, ‘People agreed to these HOA prohibitions of their own volition. It’s their right to have their own legally binding voluntary agreements and we will not intervene”. 

The other approach says, ‘HOAs have to abide by our statewide housing policy just like everyone else.’

For what its worth, I’m currently ambivalent on this matter. They’re both valid positions to me. 

First, there was Weak ADU Legislation. Then, there was Strong ADU Legislation. Now there’s Tepid ADU Legislation

Some states have ADU bills that continue to wind their way through the legislative process this year like in MA. I’ll sort these respective attempts out when they pass into law. 

Tepid ADU legislation are ADU laws that strongly deal with at least one of the poison pills for ADUs, but that do not address all of the major poison pills sufficiently necessary to actually foster an ADU movement. For reference, along with Hawaii’s new ADU legislation, I would place Connecticut’s 2021 ADU legislation into the tepid ADU legislation camp. CT’s model ADU codes were strong, but the law allowed jurisdictions to opt out, which many did. The bill’s original backers have reached the same conclusion in their own post mortem. 

A bunch of states have legacy weak ADU laws from a decade back before the ADU movement had become so dominant in the West coast. But to my confoundment, some states are actively working on enacting weak ADU legislation, such as Rhode Island’s feckless ADU law. Take a gander at how strict and retrograde this proposed ADU law in Rhode Island is. 

Pursuant to § 45-24-37(e), one accessory dwelling unit (ADU) shall be allowed per primary dwelling by right if any of the following circumstances apply: 

(1) On an owner-occupied property as a reasonable accommodation for family members with disabilities or for family members who are sixty-two (62) years old or older; or 

(2) On a lot containing a total lot area of at least six thousand square feet (6,000 sq. ft.) and meeting the minimum lot area for the residential zoning district in which it is located and which 27 minimum lot area is free from wetlands, flood plains or flood hazard areas; or 

(3) On a lot which has a minimum lot area of forty thousand square feet (40,000 sq. ft.) regardless of the zoning district in which it is located and which minimum lot area is free from wetlands, food plains or flood hazard areas; or

(4) Where the proposed ADU is located within the existing footprint of the primary dwelling or existing legally permitted or legally nonconforming attached or detached accessory structure and does not expand the footprint of the structure; provided that, the lot is zoned for residential use.

Rhode Island’s proposed law is an example of weak ADU legislation- as if written in the middle ages by some type of waspy King. 

“I declarath, if thou hast 40,000 sq ft and a wetland on thy lands, thou may hath an accessory mansion. for thy horse and its caretaker.”- Waspy King 

The current draft may represent progress for ADUs by Rhode Island’s standards, but it is weak in terms of its potential to encourage average people, or really any people, to build ADUs. 

At this point, we have ample data and research on what makes for a strong ADU code by bedfellows as strange as AARP and ALEC, from piles of housing policy journal articles, from multiple academic centers and from ADU practitioners and advocates. Everyone who studies and works on these issues in real life, is now singing from the same hymnal. 

From my perspective, there’s no reason to spend political capital on passing ADU laws that won’t produce any ADUs. I would actually encourage Rhode Island legislators to just come back to ADUs in a later session when the leadership and legislative member composition is ready to make meaningful progress on housing reforms.

Effective ADU policy requires not compromising to meet the whims of every NIMBY’s wish list–a painful bureaucratic death by a 1,000 papercuts. 

There is no mystery or debate about what makes for functional ADU regulatory reform. We definitively know what ADU legislation actually works to enable an ADU movement. 

I’d rather see strong ADU reforms fail again and again till one day, they pass, then weaker ADU reforms pass, but gain little traction. For example, Washington’s strong ADU legislation (HB 1337) finally passed in 2023 after several failed attempts beginning in 2019. Conversely, New Hampshire’s weak ADU legislation passed in 2017 but it has resulted in very few permitted ADUs.

When States are actually ready to take housing reforms more seriously, they can literally just copy the legislative approaches that have been used in Oregon, Washington, California, Colorado, Montana, and Arizona. Technocratically, these changes are not that hard. 

We just need a couple of brave state legislators to spearhead and enact these changes. (Talk to your colleagues from those 6 states above about how they did it). And ADU advocates should do their part to provide political support for strong legislation, when the opportunities arise.

Tickets are now available.

This year’s tour in Portland will feature a new set of 10+ ADUs throughout the city, never before showcased on the ADU Tour.

If you have a nifty ADU to show off, let’s talk. I’m looking for creative projects that utilize some of the new zoning allowances in Portland. I’d like to feature tiny houses on wheels, stacked ADUs, cottage clusters, and detached duplexes around the inner east side of Portland. 

Ticketed separately will be a Friday evening (9/6) ADU workshop. And, for the first time, we’re also organizing a private guided bus tour of prefab ADU/THOW factories in the Portland area that same day. Admission is limited to about 50 people for this special event. This guided tour is intended for housing policy wonks, affordable housing providers, entrepreneurs, and others who want to learn extensively about prefabricated ADU development from business leaders who are doing it. 

If you’re interested in volunteering for Portland’s ADU Tour, let me know. We can’t pull off the tour without awesome volunteers. It’s a 3.5-hour commitment and you get a comp pass to the rest of the ADU Tour that you’re not volunteering. 

ADU tours have become quite popular; in the next five months, there will also be ADU Tours in L.A., Redwood City, CA, and Seattle, WA. The ADU tour in Seattle will be held in conjunction with ADU Academy in Seattle on September 20th. 

As long as we’re talking about Portland ADUs, I’m going to include a medley of miscellaneous information about the ADU movement in Portland. 

Rate of ADU Development

The total number of permitted ADUs in Portland is now approximately 4,200, which is substantial for a city of its population. This is mostly attributable to its regulations. Starting in 2010, Portland was ahead of the curve with the strongest ADU codes in the country.

However, the absolute rate of ADU development has declined significantly since 2018. While it is only educated speculation, this is largely because most of the latent pent-up demand to build ADUs in Portland was likely met. 

Meanwhile, other creative forms of small, infill housing were legalized in 2021, such as tiny houses on wheels and fourplexes. The City also started to allow multiple kitchens in single homes by right in 2020. 

In aggregate, while the number of permitted “ADUs” may be decreasing, these alternative, smaller infill housing types in residential zones continue to rise dramatically. 

In our so-called “single-family residential zones”, in a one-year snapshot between 2021-2022, single-family homes represented only 16% of the housing being built!

This is a powerful data point for those who want to understand the economic and environmental potential for strong middle housing zoning reforms.

Charts from https://www.portland.gov/bps/planning/rip/news/2023/7/5/new-study-shows-promising-housing-production-results-residential

Leaving aside external economic realities about development from the picture (ie. increased construction costs, higher interest rates, and onerous landlord-tenant laws in Portland), there are simply more attainable housing choices that are addressing the vacuum of needs in residential zones that ADUs once uniquely filled. 

Condoization

While HB 2001 allowed for middle housing land divisions by right, ADUs aren’t considered “middle housing” under Oregon’s state law. So, the easiest way to ‘sell’ an ADU independently is to condoize it. A handful of local developers are now specializing in this. 

There have been 111 condoed ADUs in Portland, according to the Multifamily Housing Inventory. ADU condoization is already very common in Seattle, WA, and Austin, TX, representing over half of their ADU development.

Condoization of ADUs will continue to be an increasingly popular way for professional developers to build ADUs as a commodity housing product. Condoization is a strategy that tends to be used by professional developers, rather than amateur developers. But, some amateur homeowner developers use condoization as a strategy to create co-housing; there will be an example of this on the upcoming ADU tour. And, the forthcoming ADU Academy in Seattle will feature instructors with primarily ADUs-as-condos development experience. 

One benefit of condoization is it circumvents having to be a landlord, which is unfortunately perceived as being difficult in Portland. Rather, the implicit agenda of ADU condoization is homeownership. 

Selling an ADU also allows for the developer of the ADU to realize the full value of the ADU at the time of sale, rather than amortizing the value of the ADU over years of passive rental income gains. 

Analysis of ADU Permits: Not Completed vs Completed

Looking at the ADU permit submission data from 2019, here’s what the 2024 data says: 

• 294 completed
• 17 “under inspection”
• 1 issued
• 11 expired

Out of 273 total permits issued, 9% have not completed the ADU. Given that these permits were issued in 2019, it’s fair to assume these 9% of permitted ADUs will never get completed. 

Looking at the ADU permit submission data from 2020, here’s what the 2024 data says: 

• 224 completed
• 42 “under inspection”
• 5 issued
• 2 expired

Out of 273 total permits issued, 15% are still under inspection. This probably means that a bunch of them will never get completed. But, the others are most likely DIYers who are taking years to finish it, or who ran short of funds. 

A previous analysis of permits in 2017/2018 indicates that roughly 15% of those ADU permits never got built. So, it’s fair to estimate that 10-15% of ADUs permitted in Portland are never actually built. 

RMLS improvements for ADUs

Recently, the MLS used by real estate agents in the Portland metro area added a new set of inputs related to ADUs. 

While I’m not sure what the *best* database fields for ADUs are, the RMLS now includes more robust and granular data on ADUs than other US markets. 

These fields are only visible to realtors who have access to the database, but this is what the input fields look like. 

Eventually, when ADUs take hold across the country due to statewide ADU reforms, public web-based platforms like Zillow, Trulia, and Redfin, will likely display elements of this backend data for general use. Currently, the free-form public remarks text field used in national real estate search platforms give false-positive results. However, some local real estate companies are leveraging the ADU-friendly backend of RMLS to provide actual ADU-positive search results.    

By “strong” ADU legislation, I mean laws that generally align AARP’s ADU model ordinances. The other states that have passed strong legislation include CA, OR, WA, and MT.

As of the publishing of this post, this legislation has not actually been signed into law, but it is fully expected that the governor will sign this bill in the coming weeks. (Author’s note: On May 13th, 2024, this bill was signed by the Governor, officially making it the law)

Colorado is having a big year! It is expected that legislation related to upzoning near transit, parking reduction laws, and housing needs assessments, will all pass. And last month, a bill was signed into law that prohibits residential occupancy limits on housing in Colorado. 

As with California, Oregon, Washington, and Montana, the ADU legislation was passed with bipartisan support. Other states have passed weak ADU laws that have not, and will not, result in much ADU production, such as NH, CT, FL, RI, VT. These weak laws are ineffective, have little substantive impact on ADUs as a viable housing form, and as such, they do not receive comparable accolades to Colorado.

The Details

As far as the things that matter to actual homeowners who wish to build an ADU, here’s what you need to know in plain language.

The Colorado legislation requires cities of certain size thresholds to allow ADUs. This is similar to Oregon and Washington. This bill requires jurisdictions to remove “restrictive design or dimension standards” in “subject jurisdictions”.

“Subject jurisdictions” are municipalities that are in metropolitan planning area with more than 1,000 people, which includes 3,960,000 people, or 67% of the population of the state. Here’s a list of the subject jurisdictions that are ‘a municipality that both has a population of one thousand or more, as reported by the state demography office and is within a metropolitan planning organization“

To remove “restrictive design or dimension standards“, subject jurisdictions must:

• Allow an ADU of up to at least 750 sq ft. 
• Not require off-street parking
• Not require the owner to occupy the property (*more on this momentarily). 
• Reduce side and rear setbacks to 5ft (with some sub-optimal caveats)
• Not have minimum lot size requirements
• Not have special design standards for prefab ADUs

This law would also supersede rules in HOAs that preclude ADUs. It disallows any prohibition on ADUs by a homeowners’ association in subject jurisdictions. Like California’s ADU laws, these rules will supersede rules that prevent ADUs in existing HOAs. By contrast, both Oregon and Washington have deferred to legacy HOAs that disallow ADUs, but will not allow future HOAs to ban ADUs.

The zoning changes are required to be implemented by June 30th, 2025. If the zoning changes are not implemented by jurisdictions by then, Colorado’s Department of Local Affairs (“DOLA”), will have a model code to which subject jurisdictions will default. 

The other laudable provisions of the bill relate to setting up grants and technical assistance for homeowners who wish to build an ADU. The bill sets aside $8M to set up a loss reserve program that offers affordable ADU loans, and will fund programs that buy down of interest rates on ADU construction loans, assists with down payment in connection with ADUs, and provides direct loans for ADUs. 

Once ADU regulations are strong, financing ADUs is the next barrier to their development. It’s impressive that Colorado has figured out how to help address both of these barriers in a meaningful way in this bill. 

Other states should take note of this kill-two-birds ADU legislative approach!

*From Insidious Owner Occupancy Requirements to Irrational Owner Developer Requirements

I’ll now spend some time focusing on one element of the bill that merits nuanced coverage; How the legislature ultimately reconciled the bill’s original aspirations to eliminate owner occupancy requirements.

To begin with, I’ll state here in the most clear way possible: I despise Owner Occupancy requirements for ADUs with a vengeance.

Owner occupancy ordinances are racist, classist, exclusionary, morally bankrupt, and thoughtless. They are also pervasive across most of the country.

Owner occupancy requirements make me sick to my stomach.

With that said, I’m also politically practical about these matters. Whatever tactic is required to root out this insidious poison pill from ADU regulations, I will get behind. 

I provided written and oral testimony on the owner occupancy requirements for this bill in the Senate Local Government & Housing, and am attaching the written testimony below.

Late in the legislative sausage making process for HB -1152 on April 23rd, after the hearing in the Senate Local Government & Housing, an amendment was quietly inserted that transformed the original language in the bill. Below, I’m copying the original bill text with the amended bill text. 

Original bill text with amended provision in italics

A SUBJECT JURISDICTION SHALL NOT: REQUIRE AN ACCESSORY DWELLING UNIT, OR ANY OTHER  DWELLING ON THE SAME LOT AS AN ACCESSORY DWELLING UNIT, TO BE OWNER-OCCUPIED

 ….EXCEPT THAT A SUBJECT JURISDICTION MAY REQUIRE A PROPERTY OWNER TO DEMONSTRATE THAT THE PROPERTY OWNER RESIDES ON THE PARCEL WHEN AN APPLICATION IS SUBMITTED TO CONSTRUCT OR CONVERT AN ACCESSORY DWELLING UNIT. 

THIS EXCEPTION DOES NOT APPLY FOR AN ACCESSORY DWELLING UNIT THAT IS BEING CONSTRUCTED SIMULTANEOUSLY WITH A NEW PRIMARY DWELLING UNIT.

This amendment limits ADU development to amateur homeowner developers. It rules out professional developers from adding ADUs to existing single family homes. 

Importantly, this bill removes the ability for cities to have an owner occupancy requirement, accomplishing one of the key elements of the bill!

But, in its place through this amendment, it’s instituted an optional owner developer requirement. 

This amended standard will still allow the grassroots ADU movement to grow-it’s not going to kill ADUs like owner occupancy requirements do. Furthermore, this owner developer requirement will not impact financing of ADUs, one of the many problems that owner occupancy deed restrictions create (see testimony below).

The Irony of the Owner Developer Amendment 

It is ironic that policy makers fear professionally developed ADUs: 

1) Because people live in homes that were speculatively developed by someone else at some point, including the policy makers who raise the specter of speculative ADU development. Who do they think developed their home and homes around them? 

2) Indeed, the ONLY type of home that is generally NOT developed by speculative developers in the United States are, in fact, ADUs. 

This provision is like a wartime draft that only grants entry for women, children and the elderly.

It’s a totally irrational position to take.

No matter who develops ADUs, the units will help buttress the inventory of lower cost rental units and starter homes in a given community. 

The irony is that due to the nature of the real estate market in most areas, ADUs are generally developed by homeowners. My own research of permits in Portland, and an academic study conducted ADU ownership in California, both indicate that ~90% of ADUs are developed by amateurs, not by professionals. This is one of the core features of ADUs that distinguishes them from other housing types.

Irrationality aside, here’s why I actually don’t mind the amendment as a political matter

I suspect that within a few years, once Colorado legislators realize how beloved ADUs are among constituents…it will become readily apparent to a working majority of them that it does not make sense to arbitrarily throttle ADU supply relative to all other housing forms.

Colorado will come to the obvious conclusion that there’s no reason to exclusively limit ADUs to be developed by homeowners. Once this epiphany is understood by a working majority of legislators, they’ll update their ADU laws to a standard that eliminates owner developer requirements, providing parity with other housing forms. 

The other reason that I don’t mind this amendment is that Colorado cities don’t have to adopt this silly provision. “A SUBJECT JURISDICTION MAY REQUIRE”. Subject jurisdictions can simply allow ADUs to be developed by anyone, out of the gate, and they should! Adult cities like Denver can leapfrog past this baby step, and just allow professionals to develop ADUs like they already allow all other housing to be built.

In the end, the owner developer amendment may have been necessary to gain political support to ensure passage of the legislation. And, as an olive branch to the obstructionists who would not otherwise support the bill, this solution does not serve a roadblock to the ADU movement arising in Colorado.

The owner developer limitation is a quantum leap ahead of the insidious owner occupancy requirement. And, progress takes time. So, with all those caveats in mind, this amendment is a middle ground policy position that other states may look to emulate as a political matter, to move past obstinate owner occupancy sticking points in legislative policy discussions.

7/9/2023: A couple minor revisions were made to the regulations described above related to size and the subject jurisdictions.

This study laid the groundwork for a follow-up survey I conducted four years later, which used the same parameters and methods. The decision to revisit this survey was influenced by a significant policy change in April, 2021, when Portland legalized recreational vehicles as a form of housing in residential areas.

Previously, residing in mobile dwellings was part of an informal market, but it was suddenly recognized as a legal housing type. This transition, happening just a year after my initial survey, offered a unique opportunity to observe how legalizing this once-informal housing option would affect its usage over time.

Review the initial survey post for extensive description of the survey methodology and neighborhood context, which I will not repeat here. It’s worth reviewing the methodology if you’re interested in this research, as well as the additional notes toward the end of this post. 

In this post, I’ll use the shorthand “RV” for a recreational vehicle, and “THOW” for a tiny house on wheels. Together, I refer to them as “mobile dwellings”. 

Now, let’s dive into the findings and analysis of this new survey. 

A map of the locations on inhabited mobile dwellings in the Cully neighborhood in April, 2024

Here’s a link to the photo album of each of the 94 properties that I identified in 2024. (It is difficult to make out the mobile dwellings in some of the images. They’re often discreetly located or obscured by trees.) 

The photo album of the 94 properties

2024 Survey Findings

There were 94 residential properties with either an occupied RV or an occupied THOW in the Cully neighborhood.

This increase of mobile dwellings used as occupied housing was substantial – a 45% increase from 2020 to 2024. 

The breakdown of inhabited RVs vs THOWs in 2020 and 2024 respectively was:

Of the 65 properties that had mobile dwellings in 2020, 17 of them no longer had mobile dwellings on them in 2024. The other 48 still did.

46 of the 94 host properties in the 2024 survey – nearly half of all properties – were therefore new land hosts to mobile dwellings. 

At least seven sites of the 94 that I identified had two or more inhabited RVs – for the purposes of this survey, I counted these as “1” site.

Analysis of Findings

The growth of mobile dwellings being occupied as housing appears to be very significant since the prior survey

The number of residential properties in Cully that had an occupied mobile dwelling increased from 1.6% to 2.3%.

Inhabited Mobile Dwellings in 2020	Inhabited Mobile Dwellings in 2024

In Cully, the total final ADU count increased from 106 to 119 (12% overall) from 2020 to 2024. However, inhabited mobile dwellings in Cully increased by 45% over that same time period.

Here’s an image of the 94 properties with inhabited mobile dwellings, overlaid alongside the 119 properties with permitted ADUs.

As with ADUs, the absolute numbers for properties with inhabited mobile dwellings remains fairly small. But it’s clear that this form of residential infill housing is experiencing rapid adoption relative to other common housing types. This notable increase is certainly attributable to Portland zoning changes in 2021, which legalized their habitation on residential properties.   

A shift towards THOWs instead of RVs

There was a 7% shift towards using THOWs instead of conventional RVs as housing. 

I’ll also note here that in our general contracting work installing RV hookups on residential properties over the last 2+ years, the vast majority of our installations have been for tiny houses on wheels. 

To add a little bit of color to this trend, it is reasonable to hypothesize that the legal formalization of this mobile housing option has possibly bolstered homeowner confidence to “invest” in a higher quality, more expensive RV (such as a custom-built THOW) rather than using a cheaper RV option. 

An inhabited RV	An inhabited THOW

You’d never even know that some of these were actually mobile dwellings

You would never know there was a THOW in the image below. But, I happened to install the RV hookups for this project, so I know that this light blue building in the center of the image is a THOW with skirting that hides the wheels, even though it appears to be a home on a foundation. 

This dwelling is lived in by an extended family member of the primary house, which is the case for most of the RV hookups that we’ve done. 

Mobile dwellings come and go 

Here’s an example of property that used to have a THOW but no longer does. This housing form separates ownership and utility of the dwelling from the primary home, allowing for housing to be used when needed and where it is needed. 

Property in 2020	Property in 2024

In this case, the THOW has apparently rolled along to greener pastures.

Of the 65 properties that had mobile dwellings in 2020, 17 (or 26%) of them no longer had mobile dwellings on them in 2024. 

The innocuous infrastructural RV hookups for a tiny house that used to be parked here: A spigot, and a power post. 

Of course, if the current property (a.k.a- land host) wanted or needed an instant backyard housing option again, they could likely do so, given that they had the capacity to do so in 2020.

This potential for dwelling transience is one of the defining attributes that makes this form of mobile housing extremely different from conventional housing on foundations, for RV owners, land hosts, and businesses alike. 

The other factor that is extremely different from conventional housing is the relatively low cost to get the proper setup for a mobile dwelling installed on a property. 

Given the inherently low cost (generally ~$10K or so) for installing RV hookups, there’s comparatively little investment or economic motivation for a homeowner to actually use the space for a dwelling if they lose their motivation or need to do so. The going rate for renting out an RV pad with hookups in Portland (at the time this post was published) is $500-800/month. 

By contrast, if a homeowner built a $225K ADU (the average all-in cost for a 400 sq ft ADU), they would be economically motivated to keep generating income from the unit on a full-time basis for 6-10 years to pay off the initial cost of development, or to at least defray the cost of the loan that they used to build it. 

Market demand for mobile dwelling clusters in spite of the regulations

At least seven sites of the 94 that I identified had two or more inhabited RVs. 

For purposes of this site survey, I counted these locations as “1” site, but if we count them on their own, it means there were actually closer to 101 inhabited mobile dwellings on the 94 sites.

Interestingly, inhabiting multiple RVs on a residential property is not allowed by Portland. However, in my decade-long experience working directly in this field with tiny house dwellers, it is obvious to me that there is very significant demand to live in “tiny house communities”. 

The reason that Portland does not allow multiple inhabited RVs on residential properties is that two or more RVs on a single tax lot are considered to be an RV park under Oregon law. RV parks are only allowed in zones in Portland that authorize a “Residential Manufactured Dwelling Park”, which are very limited. 

Incidentally, the Cully neighborhood DOES have legacy, legal RV parks, which have many permanently occupied RVs in these zoned areas. 

Example of one RV park in the Cully Neighborhood

One shining example of the market viability of a tiny house community is Tiny Tranquility, located along the coast in Waldport, Oregon. It is fully occupied and has a wait list.

Image from Tinytranquility.com 

Similarly, there appear to be only a handful of RV parks in Portland. Of those that exist, the long-term rental spots are largely taken. I have observed that RV parks are generally in short supply in areas where land values are high, whereas there are plentiful RV parks in more rural (and less expensive) areas. 

To fix the mismatch between the demand for this obvious affordable housing solution for high value urbanized areas, and the lack of legal means to achieve it, there are two zoning fixes that come to mind. 

First, there is nothing in state law precluding Portland or other cities from changing their zoning to allow RV parks more broadly in Residential zones rather than limiting RVs parks solely to Residential Manufactured Dwelling Park zones. 

Second, the State of Oregon could update its law from stipulating that RV parks are 6 or more RVs on a tax lot, rather than 2 or more. 

Then, Oregon cities would be able to alter their ordinances to allow up to 6 RVs on a residential property without calling it an “RV park”. 

In this case, much like manufactured homes can be used to create a “cottage cluster” under Oregon state law, RVs could be classified as an alternative option for creating a “mobile cottage cluster” in residential zones. 

From Oregon’s HB 2001 Interpretation and Implementation FAQs

Neither of these two options are especially complicated or controversial. My experience is that there simply seems to be a lack of interest on the City’s part to engage on these mobile dwelling zoning solutions. 

This is terribly ironic, given the amount of political attention and capital that the City of Portland and State of Oregon are allocating to “affordable housing” solutions that now cost well north of $400,000 per door to develop. 

Legislative analysis

The reality is that RVs are already used as informal housing all over the country. This is especially true in lower-cost rural areas, but also true in cities. People create their own affordable housing solutions whether or not it is legal for them to do so.

Informal ADUs long preceded the contemporary ADU movement. It is by recognizing, legalizing, and daylighting ADUs into an accepted form of housing that we were able to foster an ADU explosion, at least on the West Coast. 

Similarly, RVs appear to be another example of a housing solution “desire path”; RVs are already the solution that average people are using to meet their housing needs. Rather than using a top-down approach to creating more affordable housing, it makes more fiscal and political sense to simply scale up this existing bottom-up approach to housing. 

Oregon law allows for RVs to be used as legal housing in manufactured home parks. What is necessary is simply to expand the entitlement of where RVs can be used as housing to all residential zones. This particular solution is not that hard, actually, as Portland has now proven.

Methodology Notes

This survey method of the 4,000 properties in the Cully neighborhood was a bit time-intensive and required expertise with recognizing this housing type, but there’s no other way to conduct this survey. 

For example, none of Google aerial imagery, Google Street View imagery, or any type of GIS analysis could provide much value in this type of survey.

There are no building permits for these dwellings. Instead, only trade permits for the hookups on the property are required, and there’s no mechanism to track those permits. And, even if there were such a mechanism, the presence of RV hookups does not indicate there would actually be an inhabited mobile dwelling located along with them (see section above Mobile dwellings come and go).

Instead, it required literally peering over fences on my tiptoes from the street, viewing backyards from strange angles, and walking down shared driveways, to catch glimpses of the tops of these dwellings in many cases as you can see from the full photo gallery. 

A shared private driveway that leads to another property, where a tiny house on wheels is parked.  Google Street view data doesn’t collect images from private driveways. See THOW in yellow box below. 

Using aerial imagery, a THOW is essentially indistinguishable from sheds and other accessory structures. 

In other words, AI can’t do this survey. 

Take that, AI. You are not my overlord.

A Request for Additional Qualitative Research on Mobile Dwellings on Residential Properties

While this type of drive-by survey is informative, it also has major limitations. It inherently lacks the ability to penetrate into the qualitative variables involved in this housing choice for both the land host and mobile dwelling occupant. 

• What motivated the owner to have a mobile dwelling on the property?
• What’s the relationship between the mobile dwelling occupant and the primary home occupant?
• Is this form of dwelling satisfactory for the occupant?
• Who owns the RV? 

There’s also many quantitative variables that it can’t address. 

• How much does the occupant of the RV pay to live there? 
• How long have they lived there? 
• What are the age and economic profiles of the occupants?
• How many vehicles are added as a result of the new occupants living in the RV?

A deeper study will require funding, or bootstrapped doctoral thesis research. If you are interested in funding additional research on this topic, or you are an academic who would like to conduct formal research to answer some of these questions, please reach out to me. I’ll share the granular locational data with those who intend to further this foundational research. 

We need to build more homes. Homeowners need the confidence to start ADU projects. How can we help? By bringing ADU to life before construction begins, before any money is spent on design and permits.

Let us explore the power of Augmented Reality in ADU design. 

One example illustrating this point is understanding the scale and how much space the new dwelling will take up in your backyard. How would it look next to the neighbor’s garage? Will it dwarf the main house if we built the ADU to maximum height? Will the oak tree be an issue?

Another example is considering the exterior look of the ADU – should it be the same as the main house? Or would a more contemporary look work?

You may indeed like a contemporary design like this.

But then, you see it next to the main house…

And you may realize that a more traditional pitch-roof design may look more appropriate.

Instances like these highlight the importance of leveraging technologies like augmented reality to mitigate risks and avoid costly mistakes during home design and construction.

Let me give you one more example: building around trees. A dilemma – a smaller home and orchard or a bigger home?

Augmented Reality (AR) enhances the home design experience. We visualize virtual homes in the real-world environment, right in the backyard. It eliminates surprises and reduces the likelihood of change orders.

We have all heard horror stories about construction gone bad. Here are two standard complaints:

• Difficulty for homeowners in visualizing the final look of their home based solely on 2D blueprints or floor plans.

• Frequent design revisions as homeowners discover preferences during construction, resulting in delays and additional expenses.

Ensuring client satisfaction can be challenging when there’s a disconnect between the client’s expectations and the final outcome. Addressing these challenges is crucial for improving the home design and construction process’s efficiency, transparency, and overall success. 

AR allows users to superimpose virtual home designs onto the actual physical space where the construction will occur. This provides a realistic sense of how the structure will fit into its surroundings.

Users can better understand the spatial relationships between various elements in the design, such as house height, room sizes, furniture placement, and overall flow. This improves the overall design decision-making process. Less analysis paralysis.

Even someone building a house for the first time can receive immediate visual feedback on design choices, allowing for on-the-spot adjustments and reducing the likelihood of misunderstandings or misinterpretations.

Homeowners with zero construction experience can actively participate in the design process. This reduces the chances of post-construction disappointment. Imagine the horror of regretting a $150,000 purchase…The ability to identify and address design issues early in the process means time and cost savings. It reduces the need for revisions and adjustments during construction.

ADU Viewer for your visual scope of work

Every homeowner wants to know how much money they need for ADU.

Cost estimation is only possible with a detailed project’s scope. How can you determine the budget before communicating what you want built? What can you build? What will fit in your backyard?

With current technology from Apple, anyone can visualize what an ADU may look like on their property. This type of visualization used to be possible only for new luxury residences. Today, pre-designed options are available for free for any homeowner or builder. 

Let me introduce an ADU Viewer – currently live in Appstore, with 67 ADUs to explore right in your backyard.

Select an ADU, select its location, push a button, and see it through your iPhone or iPad. Voila! No technical expertise is needed.

Too big? Delete and try a smaller one. Can you add some square footage? Hit “delete” and try a bigger accessory dwelling unit. Do you like the size of the bathroom and the location of the laundry? Something to discuss with your designer.

The ADU Viewer allows you to place the virtual version of an ADU in a backyard for some real-life magic:

1. One can walk around the unit, occasionally through the walls (mind the pools, please).

2. One can look out of the ADU windows and see what they will see once the unit is built. 

3. One can walk into the main house, look out the window, and check how ADU will look in their backyard.

4. One can also understand where precisely the bathroom will be. And kitchen.

5. One can explore how the new house would look if already furnished. 

Are you a homeowner considering an ADU? Take some pictures and show them to your contractor. 

What Makes A Successful Construction Project?

A successful construction project consists of multiple aspects. The activities during the pre-construction phase guarantee that your expectations are satisfied and that the project is completed within the budget and schedule decided upon.

The project scope precisely defines what the project is (a detached or attached accessory dwelling unit), the lot size and structure, the limitations associated with the project, and the objectives required for the project’s success. ADU Viewer helps you clarify your vision.

Once you have determined the scope of work, you can move on to cost estimating.

Setting a budget in the pre-construction phase after discussing the project scope gives homeowners an accurate idea of what they can expect to spend. Contractors use multiple strategies to establish an estimate, such as:

• Referring to past projects with similar requirements
• Receiving quotes from material suppliers
• Allotting finances to the professional fees

Clients can then decide the quality of materials that can be used and the luxe features that can be included in the final design.

There are still some unknowns until the construction drawings are prepared and the permit issued. The homeowner may add a skylight or a loft during the design phase. The structural engineer may call for a different type of foundation. The energy consultant may specify the verification of measures. The plan checker may ask for fire-rated walls or tempered windows. This will impact the contractor’s final bid. 

However, an experienced professional will give you a reasonably accurate idea once they see your site and future ADU.

As the name suggests, the pre-construction phase includes everything that goes on from the beginning of the project to the first day of construction. It provides you with preliminary planning, construction drawings, and a strategic plan for the project. Make our ADU Viewer a part of your process, and build an ADU faster, to budget, and on schedule.

About the author: 

Olesia Chikunova has managed her construction projects as a serial remodeler and design enthusiast since 2000. After building 5 houses for her extended family, she started to help others with their new construction projects. 

She received an ADU Specialist certification in Portland in 2019 and has been an active advocate for backyard cottages since then. She has personally applied for ADU permits in 3 counties and 11 cities in the Bay Area with a 100% success rate.

Olesia runs a company called HomeWiP that focuses on pre-construction. HomeWiP is a developer of ADU Viewer. ADU Viewer owes its name to Kol Peterson and carries ADU models designed by various architects and builders, including Prefab ADU, Inspired ADU, Livio Building Systems, Masaya Homes and SFBay ADU.

This may seem weird, but I’m giddy to share this big new ADU dataset from the West Coast with you. This is the first time that this big dataset has been presented to the public. Here, I will show why this particular data is so important, and explain why I’m proud to release it. 

Getting my hands on this data from California, Oregon, and Washington was difficult. Making it presentable was also a challenge. 

But, 10 years ago, this data presentation would have been impossible–because ADU permit data was not collected in any of these states. 

10 years ago, even if states had collected this type of data in theory, the scarcity of actual data points would have rendered the policy analysis useless, and the graphs would have been lackluster.   

But in 2024, we have three West Coast states that have adopted the ADU religion. Each has passed strong ADU legislation (although Washington’s very strong ADU law, HB 1337, won’t take effect until 2025/2026). 

Unlike much of the rest of the country, these three states have preempted the ability of homeowner and neighborhood groups to stop local ADU legislation in its tracks–the common fate of local attempts of reform, especially in wealthy (entitled) areas. 

Instead, these states are acting like grownups, and have ended the countless mind-numbing, petty, and fickle local debates about how “ADUs will destroy the character of single family neighborhoods”. 

The West Coast is years ahead of all other U.S. states on ADU reforms. These states have taken action. 

When it comes to ADU reforms, many of the country’s jurisdictions are like whining children who refuse to eat their vegetables for the 458th time. 

Just eat your greens..  

Furthermore, these three states have each instituted programs to collect and aggregate that data at the state level. 

The West Coast states deserve accolades for both adopting strong reforms, and for collecting the data to track the impact of these reforms. 

As a result of these reforms and annual data collection, we are now, for the first time in history, able to make statistical observations about permitted ADUs across the entire West Coast.  

Statewide Annualized ADU Permit Numbers on the West Coast 

So, let’s get into some charts and basic analysis:

California is the largest ADU producer in terms of sheer volume. 

CA total from 2013-2023: 88,885

OR total from 2018-2022:   3,231
WA total from 2010-2023:                8,797

Collectively, this amounts to 100,913 permitted ADUs. 

My educated guess is that the rest of the country has fewer than 10,000 permitted ADUs combined, due largely to poor ADU regulations. But other states do not collect jurisdictional ADU permit data, so there’s no way to know this number for certain. 

Let’s focus on the five years of annualized data that all three states have: 2018-2022 (Oregon didn’t start to collect its statewide data until 2018 and only collects data for larger jurisdictions).

On a per capita basis, California also leads the pack with 0.0023 ADUs per capita. This means that there’s one ADU for every 441 people in California. 

This is probably because California was the first to adopt strong statewide ADU legislation, starting in 2017, and because it has the most expensive housing markets of the three states. 

ADUs generally make the most financial sense in more expensive real estate markets, because they leverage the “free dirt” in the backyard of a single family home. Thus, it is more “rational” to build an ADU in California than it is to build an ADU in Oregon. 

While the State of Oregon only started to collect ADU permit data statewide in 2018, it is worth noting that Portland was a uniquely dominant ADU Powerhouse City prior to that. In fact, the City of Portland was likely responsible for a considerable portion of the entire country’s permitted ADU production leading up to 2017 because it was one of the only cities in the nation with strong ADU codes up to that point. By 2017, Portland already had 2,449 permitted ADUs.

When we add Portland’s relatively large permitted pre-2017 ADU baseline figure into the mix, which is reasonable for our calculations, Oregon’s total ADU permit count changes from 3,231 to 5,680.

With this adjustment, we can detect an ADU per capita range (0.0011 – 0.0023 per capita) that starts to indicate statistical equivalence.

As we will cover next, Portland’s ADU leadership mantle has been squarely handed over to Seattle and Los Angeles, and a number of other California cities, whose ADU production has recently exploded. Portland’s ADU permit numbers have actually declined since 2018.

My guess is that California’s ADU numbers will continue to climb. And when Washington’s very strong ADU law comes into full effect by 2026, we will start to see its statewide ADU permit numbers soar.

These two states have higher home values overall. California’s home values are 43% higher than Washington’s, and 68% higher than Oregon’s. Thus, it’s likely that California will continue to have a greater adoption rate of ADUs per capita than Oregon and Washington, all else equal.

Observation of the ADU Powerhouse Cities

The largest cities in these three states have a disproportionate share of ADU permits, relative to the size of their populations.

Let’s examine the statewide share of ADU permits in the three largest ADU powerhouse cities: Los Angeles, Portland, and Seattle.

On average, these cities are responsible for four times as many of the statewide ADU permits than they “should” be, compared to the size of their respective populations.

What explains the ADU Powerhouse City phenomenon?

1) These ADU Powerhouse Cities were ahead of their peers in adopting strong ADU codes, meaning they met or exceeded AARP’s model ordinance standards. These ADU Powerhouse Cities have had the strongest ADU codes amongst their state peer cities for the longest period of time:

• L.A.’s code became strong in 2017
• Portland’s code became strong in 2010
• Seattle’s code became strong in 2022

2) The cottage industry to support their development is the most robust, due the sheer population size of the market. In other words, there’s sufficient motivation for builders, designers, lenders, and realtors to specialize in the niche ADU market, because that market has sufficient critical mass of homeowner ADU demand.

3) Other factors require contextual insight to add color to the story that the data tells us:

• In L.A., people saw their neighbors converting unpermitted ADUs to legal permitted ADUs, and this inspired them to consider the idea for themselves
• In Portland, ADU tours – and abundant ADU educational offerings – have helped to normalize ADUs and foster a greater familiarity with this novel form of development.
• In Seattle, half of the ADUs are built as condo units by professional developers – and condo developers are able to build more ADUs at scale than homeowners can.

But even so, the saturation rate of ADUs per household is still low – only about 1.4 – 2.2% of households (based on household sizes as listed here) have an ADU, even in these ADU powerhouse cities. 

On a per household basis, Portland still leads the pack, but just barely. We’ll get back to these ADUs per household figures in a moment.

Top Ten ADU Producing Jurisdictions in Oregon, Washington, and California

Here’s a peek at the top ten ADU producers in each state.

It would be a useful exercise to normalize each city’s ADU production against its population size. That would help us to identify ADU Powerhouse City outliers on a per capita basis.

ADU Permit Data Inaccuracy and Constructive Criticism

There is a large discrepancy between what permit data the state collects from cities, and what cities sometimes post on their own websites.

For example, in this chart provided by the City of Seattle in its own annual report, you’ll see that Seattle’s data is a year ahead of the state’s reported data. Perhaps this is due to the administrative processes of how the state aggregates the data… government is slow and ADU permit numbers typically aren’t available right away.

The year that the State of Washington reports out Seattle’s data appears to be delayed by one. When I correct for a year lag in reported data, most of the inconsistency in the data is explained.

However, even when corrected, it’s still up to 20% off for some years, such as 2011, 2013, and 2018.

Perhaps this 20% disparity is due to clerical errors. Or perhaps it relates to which department in the City of Seattle reports this data to the state, versus which department posts the data in the City of Seattle.

While it is admittedly frustrating to have inconsistent data published between cities and subsequently by States, it’s not surprising to me.

Even within Cities, queries to various municipal departments (e.g., planning and zoning, GIS, publicly available databases) can result in wildly different numbers.

I’m not just picking on Seattle and Washington. Indeed, this type of data disparity is also present in data that comes from the City of Portland and other cities whose ADU permit data I’ve looked at closely.

Consistent database standards for housing permit data would be helpful. It’s just not prioritized or legislated in a manner that is meaningful, apparently. Perhaps in the coming years, these West Coast cities and states will be able to focus on data normalization and protocols that create consistency in permit data reporting, to assist in policy-making efforts.

Even so, I’m confident that, while the exact numbers shown in this data are most certainly not the precise numbers of permitted ADUs for the correct year in each jurisdiction, they are nonetheless sufficiently representative to be valuable as means to draw broader generalizations about ADUs, and to be used for other statistical correlations and causations that housing policy researchers may seek to analyze in the future.

As a proxy for understanding the relative scale of ADU development and for policy-making purposes, annualized and aggregated state datasets are absolutely the best tool available, which is why I’m giddy to share this one.

The Big ADU Dataset

I’m proud that I was able to collect, aggregate, and display this wonderful and rich data for you, dear reader. This ADU data was not yet published anywhere in a format that is available to the public until now. I happened to know the right people in the right organizations to help me get this data, and I happen to care enough to normalize and publish it. Otherwise, this ADU data may never have seen the light of day.

From the point of obtaining this data in their original source formats, it took hours of data wrangling to create this clean spreadsheet. As a gift to the academic and policy-making community, I’m presenting this full data set as an Excel spreadsheet file (.xlsx). While I am publishing it for public use, please credit BuildinganADU.com if you do reuse it in the future.

My intent is to foster further analysis by academics, statisticians, policymakers, and ADU advocates to draw additional conclusions.

My hope is that more individuals will conduct even more complex analysis, import external data such as home value data from MLS, Census data such as income levels and household size, or GIS data such as parcel size and lot configurations to make more insightful statistical correlations than me.

What other variables may predict where ADUs will explode in popularity next? In aggregate, this dataset has the potential to propel urban planning hypotheses forward, and to prove many other hypotheses dead wrong.

Up to this point, there was very poor data about ADU permit trends for factors that are difficult to pinpoint, but they likely relate to a lack of state legislative prioritization and direction to municipalities to collect housing permit data in a standardized way.

We are ADU housing policy Neanderthals’ fumbling in the dark, playing darts.

In the absence of good data, only through incredibly deep experiential understanding of ADUs could subject matter experts like me generate viable hypotheses about the impact of regulatory policies that stymy their development.

The data itself has been inadequate for drawing absolute conclusions up to this point. To the extent that it could have helped, the analysis would’ve been flawed, because the data has been so fragmented, sparse, and not normalized.

Actual policy conclusions are very granular and contextual. Even with the assistance of big data, many other factors will likely play into what type of ADU movement we could expect to see. 

For example, one day in the future, with big data, we may be able to predict which cities have the “most affordable ADU potential”, by analyzing cities that have snout houses built in the 1970s (ripe for a garage conversion because they have no off-street parking requirements), who have larger households or a severe housing shortage, or whose households own their property for sufficient years (such that they have the accrued equity), because interest rates are dropping to below X%.

Perhaps one city has a sufficient freelance construction labor market and cottage industry that is capable of working with homeowners to build custom ADUs and has the capacity to do so, while a different market only has a limited supply of laborers who are already aligned with professional developers and, therefore, the construction of custom ADUs is not possible. But, while this latter city would lack the capacity for custom ADU development, it may be an especially ripe market for prefab ADUs. 

We may be able to determine which neighborhoods have sufficient demand for housing development, and where an entrepreneur should focus their energy and financial resources to do condoization of ADUs. An entrepreneurial company can offer to ‘buy the backyard’ for $150K because they can speculatively make the costly development of a detached ADU pencil out. Indeed, we are seeing the sketched contours of this business model started to occur in the Bay Area, Austin, and Seattle. 

The Wildly Inaccurate Data Analysis of Freddie Mac

In the many articles written about ADUs, you’ll note a paucity in statements about how many ADUs there are. That is because, prior to this post, there was no data to make such claims. This data makes such data speculations defensible, as I have done earlier, where I speculated that there are likely 110,000 permitted ADUs in the US. 

Where such claims do exist, they came from other methodologies, such as this MLS study of ADUs based on real estate listing text mining conducted by Freddie Mac in July, 2020. But, this report from Freddie Mac is wildly inaccurate if we’re interested in looking at the number of permitted ADUs… It’s off by orders of magnitude! That is because this study included informal ADUs. The problem is that the gap between formal and informal ADUs is vast. Their study concluded that:

“In 2000, 1.6% of active for-sale listings had ADUs. By 2019, the share of active for-sale listings with ADUs had grown to 6.8%. In terms of numbers sold, less than 9 thousand or 1.1% of homes sold on MLS in 2000 had ADUs. By 2019, sales of homes with ADUs grew to nearly 70 thousand or 4.2% of homes sold on MLS.”

In the most prolific markets in the entire country (i.e., Portland, L.A, Seattle), only ~2% of all households have a permitted ADU. As it stands currently, Portland has the most ADUs per household of any large US city, as described in the Powerhouse Cities section, and only 2.2% of households have an ADU in Portland. 

So it is grossly inaccurate to state that 6.8% of all homes in the US have an ADU. The answer may be more like 0.068% or 0.0068%. While I wish 6.8% of all US homes had permitted ADUs, we’re probably 100 years away from that day. 

Freddie Mac’s research does show that realtors are now more likely to state that a listing has an (informal) ADU because the concept of an ADU has become popularized in the last decade. 

While the Freddie Mac research is misleading in terms of conveying how many ADUs there are, it is helpful in showing how large the demand has become for ADUs. 

The delta between the number of informal ADUs (6.8% of households) and the small number of permitted ADUs per household (0.068%?) shows the potential of better ADU codes to help bring permitted ADUs into being. 

Obstructive ordinances prevent the legal development of permitted ADUs, and cause informal ADUs to flourish. 

I raise Freddie Mac’s study to show the importance of the data that I have collected here. Unlike Freddie’s Mac reliance on MLS textual data, the data that I am presenting is based on actual permitted ADUs — inspected and approved by building inspectors.  

Conversely, MLS textual data is based on mythology and marketing and hopes and dreams. It has no bearing on the reality of how many actual permitted ADUs there are.

The researchers of the Freddie Mac study were working with the best information that they had and using a logical method. Federal, state, and local policy is made based on research done by entities like Freddie Mac. 

But I can tell you that my data is (relatively) right, whereas MLS textual data is very misleading. Those numbers could result in problematic analysis of policy causation and impact. 

I’d like state and local governments to clean up their building permit data so that we can get a better understanding of ADU policy. 

Fun with Dynamic ADU Charts
Finally, from this link, you can see annualized ADU permit charts from all cities up and down the West Coast.

Here’s the graph of ADU permit data from Berkeley, California.

Here’s the graph of ADU permit data from Bend, Oregon.

Or, this one from Bellingham, Washington.

Ever wondered how many ADUs have been permitted in your West Coast city?

Wonder no longer.