25 points are needed annually to remain ‘current’ and I have 12 thus far. These are from the 6 hour mould seminar with Caoimhin Connell for the PCA and my full day spent with Graham Coleman last month, receiving one-to-one tuition on damp diagnosis.

Why bother? Well, I believe that in life, we never stop learning and there’s always something new to discover. Clients rely on surveyors for up to date information including the latest regulations and methods. Many PCA members already take their on-going training and development seriously, but up to now they’ve had no way of demonstrating that or enjoying a structured program of self improvement. It’s reassuring for customers too because let’s face it, some of us are not getting any younger and on the one hand clients like to think they have an experienced surveyor working for them, whilst on the other they don’t want somebody who qualified 30 odd years ago and has not kept up to date. Clients now  have the best of both worlds – experience and proven currency – brilliant.

I have two CPD presentations in the pipeline (one for structural repairs and one for damp and condensation – both for groups of RICS surveyors) and a session talking to Leeds building Surveying students about damp, plus I am mentoring a student for a days Damp & Timber surveying next week.

My NVQ level 5 in occupational health & Safety starts at the end of the month and I hope that counts towards the scheme too.

I think that the Property Care Association is once more demonstrating that as a trade association they are serious about maintaining standards and they should be applauded.

Mind you – those members that don’t subscribe to this ‘optional’ CPD scheme, may find themselves having to explain why not in the near future, as those who do subscribe start promoting the fact…. like I have here.

Dry Rot

Click here to view pdf..

Back to school for more damp diagnosis training.

Graham kindly invited me down there for an intensive day of tuition on a one to one basis. I’ve attended many presentations and training courses with Graham, usually at the Property Care Association’s HQ and I jumped at the chance to visit him.

About half the time was spent on the computer playing around with data from some of my damp surveys done around Yorkshire using Lascar humidity and temperature data loggers. Graham has refined his bespoke spread sheets to enable extrapolation of RH’s at various air temperatures so it is easy to simulate the effects of raising or lowering the heating in a house effected by mould or condensation. We produced lots of graphs and discussed the best ways of getting the message across to clients, without confusing them with the science.

Graham has been using ibuttons to compliment the Lascar data loggers, allowing simultaneous surface temperature readings to be obtained, to add to the diagnostic process. These are great little toys and I’ve now bought a starter kit with the software and Graham actually gave me a couple of ibuttons to get me started off.

Graham fires up another set of data logged humidity readings

We then moved onto gravimetric testing and Graham showed me his lab equipment and took me through his vast collection of lab books, going back decades. Leafing through the books was an eye opener, with all the neat columns of total and hygroscopic moisture contents from thousands of samples he’s analysed over the years.  He looked me in the eye and said “if you compare the results from these profiles they almost always agree with the profiles obtained using a conductivity moisture meter”. That’s comforting for me, bearing in mind that i specify almost all my work using my Protimeter MMR.

However, for precise accuracy you cannot beat the gravimetric method, which allows calculation of the capillary or free water content, as opposed to the hygroscopic or air dry content. The basic method is described in BRE 245 but of course Graham has such great experience and carefully took me through the methods and equipment he’s found works best – priceless knowledge for me to use for the benefit of my clients and I’m very grateful to Graham for taking me under his wing.

Furniture moved - the cold blue area shows why mould finds these places so healthy.

We also messed about with Graham’s infrared camera and this is the cold spot we found when we pulled his pouf away from the lounge wall – quite a temperature difference eh?

Salt testing was covered and Graham is coming up to my Sherburn in Elmet office later in the year, for another master class – I can’t wait!

Dry Rot.

In saying that I do sometimes recommend installation of a new one, depending on the circumstance. Here’s why.

 Bridging built in

Often these houses had the potential for rising damp built-in from the start. They all have traditional bitumen damp proof courses and at only 60 or 70 years old, these should be working. The thing is though, after the war traditional building materials were in short supply. Timber in particular was hard to come by.  You can see this when you enter the houses. There’s often a increase in the use of solid concrete floors and the joinery is of small section; deep moulded skirting’s and architraves disappear and tiny plain bull-nosed and chamfered items come in. I see this all over Leeds and the rest of Yorkshire.

Surprisingly, even this change impacts on the results of my damp survey, a few decades later.

As an example I’ve included a survey from this week; North Leeds in West Yorkshire, a damp survey for a home buyer.

The house has solid floors and cavity walls.  The solid floors lack a DPM, but the bitumen DPC is there, visible in the external brickwork.

Symptoms of damp include perished and salting plaster (lime based), on many of the walls including internal dividing walls, party walls and the inner skin of the external cavity wall. Profiling with my protimeter MMS in conductivity mode reveals a nice rising damp profile to match the damage.

However, the rising damp is only there to a height of around 150 to 250mm above the small section skirting. It is much higher on the chimney breast piers though, at around 700mm or so.

Now then,we all know that evaporation is a major factor in controlling how high damp rises, but I’ve seen it 600 or 700mm high on a single skin internal dividing wall many times, why not here? The images show the base of the wall with the skirling removed and the DPC exposed. You can see that in fact the bed-joint housing the DPC is about 50mm above screed level. The skirting boards are also about 50/60mm deep. Any plasterer will tell you that stopping lime render and finish 35mm above the floor takes care and effort, so naturally the plaster was applied down to the solid floor (in fact in some rooms the plaster extends down below the screed level).  This does two things in these cases:

It bridges the DPC allowing capillary action to bypass the DPC and rise past it and into the plaster and brickwork above the skirting’s

It allows the damp strip along the floor/wall junction intimate contact with the rear of the skirting boards.

Whilst the DPC is well bridged, some of the capillaries available for continued passage of damp are broken at the interface between the plaster and the brick. The wood absorbs some damp too and when you think about it, at only 15 to 20mm thick the ‘bridgehead’ if you will, is much smaller than the area of the base of a wall is, had it no effective DPC.  Not surprisingly the rising damp though damaging, is maintained at a low level.  Salts are still concentrated in the evaporation zone and the lime plaster has failed as a direct result.  The skirting harbours wet rot and wood boring weevils are breeding there too.

Remember, the floors have no effective damp proof membrane below them, so they will remain moist. Why not break them up and replace with a membrane and modern insulation? That would be a great idea and would allow a nice sealed waterproof joint at the DPC level too. However, the existing floors are generally level and true.  There’s no signs of sulphate attack, cracking or even any salting. Can we save the client some money? It will cost many thousands of pounds to replace all the floors.

Oh and another thing – some of the floors were laid after the walls were plastered, so the lime plaster is embedded in the concrete in places and so are some of the door frames and such.

What to do?

Let’s forget I am a damp specialist for the moment and think. What damage has this done?

The skirting is decayed

The plaster is perished to varying heights

You could just re-plaster and replace the skirting. That is one option. The problem may re-occur but hey, it took decades for the damage we see now to become a big issue. It’s an option.

As a specialist I want to leave the building and know, that a re-occurrence is either decades away, or will never happen.

A solution for internal bridging

Specification.

The client wants to retain the floors so here goes…

1. Un-bridge the DPC by removing the plaster to at least 300mm past the last extent of the rising damp profile
2. Rake out a chase (water proofers sometimes call this a reglet, but it is only extending into the floor, not into the wall), around the wall/floor junction and clean it all the way up to the DPC (about 50mm high). Remove the lime plaster from the chase; it’s too friable and soft to seal effectively.
3. Point up the chase with a good quality cementitious mortar; preferably a polymer modified one to reduce the chance of cracking
4. Apply a couple of coats of a liquid applied DPM, like Safeguard’s DryBase. Making sure that the material laps up past the DPC and extends out past the proposed bearing of the new skirting boards, door frames and architraves

The above has solved the bridging issue and the client can have the walls plastered and fit new skirting  too.

More specialist work.

We are not there yet though. For starters, the base of the walls have been subject to a cycle of wetting and drying and there are the salts to think about. Modern plaster like gypsum act like a poultice on a wound in these cases and greedily absorb the salts, becoming hygroscopic themselves and failing. Lime mortars too, will do this. There’s nothing for it, we’ll have to take these into account by:

1. Applying a dense sand/cement render which will not allow any residual water to bring dissolved salts into the material or;
2. Dry line the walls so that the lightweight modern (or lime based traditional) finishes are completely insulated from contact with contaminated brickwork and bed-joints.

In this case the client has chosen a render, which let’s face it, is much cheaper, especially as the damage is confined to a narrow strip around each room and ‘patching’ a dry-lining is a none-starter.

There’s more though.

Despite the evidence of my eyes and my experience I cannot know whether the bitumen DPC is in perfect condition can I? The DPC is clearly bridged and we are going to fix that. But, is all the damp due to the bridging?  Could some be due to small breaks in the DPC or a lack of a DPC in places?

It’s clear that there is no DPC in the chimney breast piers. They are to be exposed and the hearths ripped out as part of the buyers plans. So I am installing a Dry Zone chemical DPC in these piers. They are very salty too, so the render needs extending, though as they are salty high up, a dry-lining option is recommended here, instead of the render.

The rest of the property is quandary though. Costs so far are quite high; The Chasing work, hacking off, floor/wall sealing, plastering skirting and waste disposal.  Every room is effected so that’s quite a lot of disruption.

So I’ve given my client the option of installing  Dry Zone DPC into the rest of the walls, just above the old one.  Modest cost and there as an insurance against having to do anything in the future if there is a break anywhere or if in a few decades the bitumen finally gives up the ghost.

In addition, as the client wants to keep the floors, he has an option of a surface DPM applied to protect any timber floor finishes he wants later

Rising damp – it’s not always straightforward. However by taking the time and trouble to get to the cause and explain the situation to the client so he/she can make an informed decision, we have a solution which should meet the customers needs.

Dry Rot

PS – damp diagnosis and solutions in Yorkshire by the author are available here

Damp slate laths under spray foam

many don’t like it…it just seems wrong.  Especially in this case when it’s been used in an 18th century grade 2 listed building in North Yorkshire.

I was called in to check the roof for a potential buyer. The RICS chap had condemned the entire roof on the basis that this foam had been used.

I found some light infestation by common furniture beetle but generally the roof timbers were fine. However, there was a bit of staining here and there and moisture meter readings from the exposed rafters confirmed some of these were leaks.  Externally there was some evidence of the odd slipped slate and this did correspond to the stained and damp areas.

However, I though I’d do some investigation work on the unstained and apparently dry areas, as a way of checking out people’s opinions; that  the spray foam can trap moisture in, which on face value seems a logical position to take.

Using a combination of deep probes and eventually by picking some foam away, to confirm what I was finding, the following results were found.

The rafters and trusses were dry, where they were exposed (11 to 16%)

The upper sections of the rafters and the slate laths were almost all on the damp side, ranging from 19 to 28%.

Now then.  The roof is old so I don’t think the laths are heavily treated with a salty preservative so why the high MC?

As can be seen the roof void was being assaulted by twin bathroom extractors venting into the void..never good.  So maybe that wasn’t helping. Could it be though that a high MC is there due to the reduced ability of the laths to dry out after getting wet, through inevitable condensation on the underside at night?  This seems likely.

Steam gone but not forgotten

Anyway, I didn’t agree that a new roof was in order, but I have put the new owner on notice that regular planned maintenance is an essential part of looking after this building and maybe the life of the  roof may be shortened by the presence of the foam.

Dry Rot.

Our houses are built from stone or brick, usually bonded in cement or lime mortar.  These materials soak up water, whether from the exposed surface when it rains or from the ground, after all, they are embedded in the soil.

Rain is sporadic and interspersed with sunshine and wind, so the effects of rainwater penetration are mitigated to some extent by the evaporation cycle.  Cavity walls are the modern way of almost totally eliminating penetrating damp.  Rising damp though, is different for several reasons.

The ground gets wet when rain falls, but evaporation is reduced by a number of factors, including the earth’s ability to soak up lots of water, particularly at the foot of a wall; the ground soaks up not only the rain which falls onto it, but also the rainwater which hits the wall and runs down to the ground or settles there, due to the topography of the site.

In the case of ground adjacent to walls, there’s also the soil structure to consider; it’s been dig out to form a foundation and then in-filled again, so it is usually less well compacted than it was was before building commenced; it’s a natural sump, against the building.  The upshot of this is that the ground gets very wet and has not fully dried out, before it gets wet once more.  As a result, it’s often damp almost all year round.

Buildings are built into the ground at the base; surrounded by this damp earth. So the bit of the wall below ground level soaks up this water and becomes quite saturated. Whilst the building material is denser than the soil, it is much more homogenous; bricks or stones in regular bed joints and sometimes quite thick. This means that the capillaries are more continual and smaller. If anything the wall at and below ground level will retain this water with more enthusiasm than the soil it sits in.

Whilst less dense materials soak up a larger quantity of water, than dense ones, they also let it go faster too. This is because the smaller pores in dense materials exert relatively more ‘suction’ than larger pores. So the base of the wall is the last thing to dry out – if it ever does in Yorkshire.

It’s not all bad news though; the section of the wall above ground level is usually isolated from the base by a physical DPC. Without one of these the material will draw the moisture up the wall – classic rising damp. All the DPC does is offer it’s bitumen or plastic upper face to the wall above, so that the naturally absorbent materials rest upon this dry surface.  Below the DPC are pores and capillaries full of moisture, perhaps less that a couple of mm away from the wall above.

Now then, what if we remove, damage or bridge the DPC, so that the wall above has a connection to the wall and ground below? Will dampness be drawn up the wall also?  The answer is almost always yes. The height depends on many factors but some spread of the moisture is inevitable.

This happens slowly at first but will normally accelerate as the building materials ‘age’, the exact reason for this is not fully understood, but new cement mortars are more resistant than very old mortars or lime mortars.  Nevertheless, it will happen eventually, as seen on the images above. The top image is from a six year old building – the lower image from a 100 year old building.

Look at the top image.  It is a six year old prestige office building in Wakefield. The DPC is a heavy duty plastic type and there’s nothing wrong with it. The damage seen in the image is caused by rising damp and rainwater splash at the base of the wall. The DPC is out of view, only 5 to 75mm below the path and resting on a course of engineering brick. The severe damage is confined only to the sections of wall where the path is higher than the DPC; the building is a great example of the negative effects of having the ground even slightly higher than the DPC - bridging it.

On other parts of the building, where the ground is just below the DPC level, the damage is very slight because only rainwater splash is involved there.  Note that it is stone and the damp is clearly rising up within the stone, crossing the cement bed-joints and concentrating salts in all the materials. It’s hard to se on the image but the stone is already spalling at the base due to the last 6 winters of freeze/thaw cycle.

Rising damp is a very common problem because it is a natural consequence of building anything on the damp earth without insulating the building materials from the ground. A DPC is the building’s essential equivalent of a camper’s ground sheet – try sleeping in a tent without one!

However, diagnosis is important, so that remedial action is appropriate and effective. There are damp specialists who, having passed an examination called CSRT, can help to establish the cause.  Experienced building surveyors can be consulted too.

My advice for the client in Wakefield is simple – lower the ground and allow the existing DPC to work properly.

Dry Rot.

I use Lascar data loggers and have just bought Lascar’s latest offering; The Data Pad, and I’m reviewing it here.

Data loggers are just sensors with a memory chip inside and all they do is collect a set of measurements at fixed points for analysis later.  Time lapse measurements are crucial in getting real information and avoiding the snapshot readings via a hand held hygrometer and thermometer; measurements on the day may be way off the average or miss important fluctuations. This approach is growing and was introduced to me by Graham Coleman of the Property Care Association, who has included instruction on their use and on psychrometrics for a number of years, as part of the PCA’s Damp Diagnosis and condensation course. That course is a well respected one and I’m sad to admit that I’ve sat through four times and I’ve seen it evolve over the years, getting better every time.

Let’s face it, how many times has a damp surveyor arrived at a mouldy and apparently dry house?  Only to be told by the frustrated owner “Well it was really wet yesterday, you should have come then”!  Data logging solves this problem.

Anyway, up to now, I’ve had to take my laptop to site, to set the loggers up and download the data.  This takes time and means that I have to have my valuable laptop on hand.  Why not set them up at the office Bryan?  Well, until I survey the building I don’t know how many I’ll want to set up, where to site them or what to name them (if you look closely you can see the report number, followed by a location prompt on the screen 2 below –internal -  back bedroom).

I’ll need at least two, but sometimes more, if the house is larger and there are widespread problems with mould or damp.  I only used two at the Harrogate survey.

The Data Pad replaces the computer for setting up and downloading data.

It’s about the size of my blackberry curve or maybe a little smaller.  A simple case with a USB socket, small colour touch screen and a power switch. I surveyed a property in Harrogate a couple of weeks ago and set up two EL-USB-2LCD+ loggers there. I chose the locations after the survey, so I had to have my laptop to hand to do this, however, having received my Data Pad last Friday, I collected them today and left the laptop in the office.

Switch the unit on and a welcome screen gives way to the option screen at the top of the page:

Insert the logger in the USB on top of the unit and the unit acknowledges connection and you can select by just touching the screen to either: view data, set up a new logger or stop and download from one as I have below: ( There’s also access to the unit’s settings such as time and  unit measurement too)

The data comes down in a moment and you can view it as a graph with your three plots and any alarm levels you set previously.

Back at the office just plug the unit into the USB and it’s recognised as a new drive – just drag or copy the files to your folder of choice and open with Lascar’s EasyLog software.  From there it’s a snip to export to a spread sheet and get the essential information you need to find out how the internal and external environments are acting.

Do you need it?

Well, it’s not essential, as the laptop will do.  But if like me, your laptop is slow to boot up (damn that Vista) and if you don’t fancy lugging an extra case around on surveys, this is a snip at only £120 + VAT. It can hold up to 500 data files and I was able to get it working without even reading the quick start guide; it’s that easy.

Top marks to Lascar for a simple and very neat tool.

Dry Rot.

Last week I was in a roof void in Horsforth, carrying out a pre-purchase timber survey for a client. The obvious infestation in some of the roof timbers had already been noted and I thought I’d pop something up on the blog for those who are not familiar with The Bark Borer Beetle Ernobius mollis.

This insect shares many of Common Furniture Beetle’s visual’s such as similar exit hole diameter and even the adults look similar.

Anyway, the video below tells the story and I’ve also taken a close-up macro shot of the frass for you.

Here’s the macro image I promised you.  Note the pellets reflect the food – almost black through to buff colour.

I have come across treatment guarantees for work done in roof voids, where this was the only infestation, so it does pay to get diagnosis right. Any self respecting timber surveyor with CSRT will have had to demonstrate his ability to identify these common insect species, but there are many untrained ‘specialists’ and some building surveyors who don’t always get this right.

Remember, the bark may be missing, leaving the tunnels and some exit holes clearly visible.

Dry Rot

Why?  Well there’s a growing band of people who believe that mould in houses is a serious threat to health and they are busy putting forward this view.  Others (like myself), are sceptical. We decided we needed an independent expert’s help.

His presentation was broken onto five parts:

1. Moulds and fungi – a basic introduction.
2. Fundamentals of Toxicology
3. Mould and Illness
4. Sampling strategies and data interpretation
5. Control strategies (Assessment).

Caoimhin didn’t mess around and it still took all day to get through the above, so I’m going to keep my review brief. This blog post is parts 1 & 2. I’ll post the others later.

Part one – Moulds and Fungi

This section was fascinating and Caoimhin filled in lots of blanks for me – moulds are just fungi, like dry rot, wet rot or mushrooms.  However, they are in fact any filamentous fungi and don’t need to be small. They are ancient species and occupy virtually all environments from snow, to desert, to leaf litter and even our bodies (think thrush and athletes foot). All air samples contain mould – ALL.

Recognising mould species by eye is hard because they vary so much, even within the same species – with sexual and asexual states. Many moulds have more than one name, though only one genus. (later on Caoimhin explained that the species is irrelevant in most cases anyway).

Mould needs moisture to grow and food too. Food is everywhere so water is the factor which kicks off and sustains mould growth. The spores are produced and expelled for procreation and not all the time, so a growing patch of mould does not mean an automatically high spore count in the air (not that a high spore count matters anyway – see part 4).

We’ve lived with mould for millennia and there are still over 1000000 which haven’t been named yet. They are used in food, beer, marmite, wine, cheese, salami and drugs too.

Part Two – fundamentals of Toxicology

This was my favourite part because it put those terms we see in many newspaper reports in a new context.

Caoimhin went through the difference between toxicology and pharmacology. Hazard and poisons were covered – did you know that one of the toxic chemicals which mould experts say is going to kill you is found in ALL peanut butter too? Doesn’t matter though, the quantity is tiny and as Caoimhin told us “The Dose makes the poison’.  And the dose is minuscule where mould is present.

A harmful substance can be present (like bleach under the sink), but the risk is tiny (it’s sealed in a bottle).

But the best bit for me though was the section on Epidemiology – the study of occurrence of end-points. He introduced three common concepts that are used (and abused).

• Association
• Correlation
• Causation

Mould is Associated with ill health!  Sounds reasonable and is found in lots of mould experts adverts web sites and such. So what is an association? Sounds bad eh?  In fact from the Epidemiologist’s point of view Association is almost less than nothing. It only means that an observation occurs with another observation – without further quantification.

For example (this is lifted straight out of the presentation).

• “…the last person who lived in this house died of lung cancer”
• “….the last five occupants of this house died”

• FACT – “Occupation of this house is associated with death”
• Fallacy – “This house is causing people to die”.

Facts:

• Virtually all people who have ever died lived in a house
• Absolutely all people who live in a house will die.

It follows then that associations are misunderstood by laypeople like me. If I see that the Daily Planet says mould is associated with illness and death I take notice.  What a con! Using scientific speech out of scientific context causes this and is the stock in trade of those who would have us fear mould.

Correlation.

• This is a type of quantified association.
• Stronger than an Association
• Required for causation but independent of causation
• An event is observed to change with another event.

The correlation could be positive or negative.

In some studies the positive/negative bit is used to confuse readers. For example one study of Radon gas showed a correlation between lung cancer and radon levels.  Sounds fair? yet when the data was checked the correlation was negative and less people died of lung cancer in the houses with the higher radon levels….counter intuitive and a surprise. This does not mean Radon is not bad for you –it just means that the report misinformed the reader in that case by not stating which way the correlation pointed.

Causation

• There must be a plausible biological response
• There must be a strong and consistent correlation
• The event, when removed, must result in an effect that fails to appear.

This is important because from an Epidemiologist view there is a confounder where mould is concerned – there is no causation resulting in illness associated with mould

I found this bit easy to understand and very refreshing.

Then it got a bit more complicated.

Caoimhin used shots of whisky poured into a tank of fish to demonstrate toxicity. This was fun and also very illuminating for a none –scientist (no fish were harmed, it was all done with slides).

So 15 shots were tipped in and 90% of the fish died

So the reference level (RfL) is 15 shots with a result of ED90

Some survived, so we see that not all members of a group respond to the same dose in an identical manner. Most died – these are the majority and death was the average effect of 15 shots. Of course, those who were sensitive died too, only the tough few (1), survived.  These are the resistant individuals.

let’s try an RfL of 10 shots…

This time we get an ED50, so half the fish died.

Now try five shots RfL 5 = an ED10.  The opposite of the results with RfL 15 – now only 10% died.

Ok, we don’t want anyone to die – what if these were our children and not fish. Three shots it is – RfL 3 – no deaths.

We now have a new term NOEL – No Observable Effect Level or. The Lowest Observable Effect Level (LOEL).

This means that at these concentrations we are at the lowest level at which there are statistically significant increases in frequency or severity of adverse effects.

So the lowest Observable Effect Level is used to:

• Establish a reference dose
• Establish a reference concentration

The reference dose is an estimate, with attributed uncertainty of daily exposure levels, including sensitive populations, that is likely to be without appreciable risk or deleterious effects during a lifetime.

The trouble is that these RfD and RfC’s are heavily weighted:

Uncertainty factors

reductions in the LOEL to account for known uncertainties.

Modifying factors

Reductions in the LOEL to account for unknown uncertainties.

This means that caution is used and a RfD of say 0.05mg/kg/day, may have been derived from a LOEL of say 1.0mg/kg/day – 20 times higher!

So it’s the uncertainty which drives science – as Caoimhin puts it – “Uncertainty is the heart and soul of science”.

I’ll skip the statistics and get to the quick –

What is a poison and how much is too much?

So what are these toxins in mould?

Lets go for the daddy of them all Trichothecenes. These are monstrously toxic and can be produced by the black mould Stachybotrys atra. They are officially classed as extremely toxic:

The LOEL is 0.03mg/kg/day

LD50 is 1mg/kg/day

LC50 is 200-5,800 mg*min/m3

So if you have Stachybotrys in your house you’re in danger, right?

In a very mouldy house covered with 500ft2 of the mould a study found 16,000 spores m/3. This was a flooded building – not cleaned, full of visible mould.

The Trichothecenes were measured very precisely:

the amount per m3 of air was 0.0000013 mg/m3 or 1.3ng/m3

Well the NOEL is actually 0.11mg/m3

So the amount in this mould city was about seventy six thousand times lower than the NOEL which is the No biological observable effect with inbuilt certainty and uncertainty.

From this the level of spores can be calculated thus:

Noel = 3000,000 spores /kg are needed.

The air concentrations needed to deliver that dose are to humans in 24 hours are:

Infant 2,100,000 spores/m3

Child 6,600,000 spores/m3

Adult 15,300,000spores/m3

The expected spore concentration in a house heavily infested with Stachybotrys is <200 spores/m3

Adult hazard quotient is 0.0000013 (virtually zero).

The story is the same for Aflatoxins, Fumitreorgens, Satratoxins and trichoverrols – even at 10,000 spores per m/3 (the very maximum you are likely to get in a very mouldy house), the amounts are below the LOEL by orders of magnitude.

Remember that the LOEL’s include susceptible persons.

Also, bear in mind that these complex chemicals are organic and are expensive for the mould to produce, so they are not manufactured for nothing. Moulds will produce these toxins is direct response to competition from other moulds. So most of the time they are not in ‘chemical warfare’ mode, they are in keep growing mode. Presence of mould doesn’t mean presence of toxins.

MVOC’s

And another thing – MVOC’s Microbial Volatile Organic Compounds.

These sound bad don’t they? The thing is though, that the long list of terrifying toxins above are all large complex molecules, so guess what?  They are not volatile and do not form part of the MVOC’s. The smell of mould is due to MVOC’s which though unpleasant are not in any way associated with the toxins we are told to fear…..no mould fear monger will tell you that.

Remember – as I said above, toxins are there for a reason, why evolve a mechanism to makes these toxins and  then waste them, by spitting them out into the air as volatiles? They are needed at the point of growth, where mould meets mould in a fight for territory, on the surface of the growing medium- not in the spores, which are basically seeds anyway; merely a packet of DNA waiting to settle somewhere moist.

What all this amounts to is that toxicity without quantification of risk is meaningless. The toxic mould crowd focus on toxicity and ignore the risk – which is vanishingly small.

see a short video of the day here PCA mould Seminar

George Dunnett’s experience with the CSRT Course run by the PCA

About the author.

I am a Chartered Surveyor working in North London and currently undertake residential mortgage valuations and Homebuyer Surveys. Early in the year I decided to study for the Certified Surveyor in Remedial Treatment qualification (CSRT), run by the Property Care Association in Huntingdon. Bryan Hindle has kindly asked me to write a review of the course, to perhaps try to encourage other chartered surveyors to consider it too.

I think the need for a better understanding of timber and dampness related defects by chartered surveyors is vital, not least because of the very considerable cost to the homeowner of either misdiagnosis or inappropriate remedial treatment. A better understanding of these issues by chartered surveyors will lead to fewer unnecessary timber and damp referrals. This will be profoundly beneficial to homeowners and to the home buying process in general.

Passing the course not only allows you to use the letters CSRT, but more importantly, provides formal confirmation that a certain level of knowledge and understanding has been achieved.

The Course.

The course is split into three modules.

1) Legal and health and safety aspects of remedial treatment;

2) The identification and remedial treatment of infested timber;

3) The identification and remedial treatment of dampness.

The course has been designed for those actively involved in the remedial treatment industry and therefore a certain level of practical understanding and a degree of hands-on remedial experience is expected.

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The legal and health & safety module is the topic that helps you understand and remain legally compliant when undertaking remedial timber and damp services. Steve Hodgson makes the topics (which could be quite ’heavy‘) relevant and amusing, bring into the discussions practical examples of how the law is interpreted.

The legal aspects of this module include The Party Wall Act, environmental and contract legislation together with the Law of Tort. The health & safety topics include the H&S at Work Act, the H&S Management Regulations, Control of Substances Hazardous to Health and the various regulations relevant to on-site remedial work.

This module provides a sound basis upon which to undertake remedial work and property inspections safely and within the law.

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The Timber module was of particular interest to me, having been an apprentice trained carpenter and joiner in the early 1980s and a life-long woodworker.

The timber module is split into two sections: the first covers insect damage, while the second investigates damage caused by fungi.

The CSRT Timber syllabus is a real treat. Not only do you have Graham Coleman providing the expert tuition, there are also high quality photos and timber samples showing precise details of the different types of fungal and insect damage. This course will probably be your best opportunity to “nail” this subject. The course material and tuition is first class.

The level of knowledge and experience Graham Coleman brings to this topic is quite amazing. What is also impressive is how he manages to present the information in a clear and uncomplicated manner for students of varying backgrounds and experiences; even a Chartered Surveyor can understand it!!

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The final element of the course is the Damp Syllabus. This was my particular reason for joining the course, since it presents me with the biggest challenge in my work.

Graham Coleman once again sets-out dampness and its various manifestations in a clear and impartial manner. The science behind “rising damp” is explained along with the physics of condensation.

Graham’s impartiality and objectivity in this topic is important, since such is the level of polarised opinion with damp issues, some potential students might be put off, simply by the course’s title. This is a shame since there is much to be learnt. I can certainly confirm that there are no agendas at play or dark forces at work.

My particular eureka moment on the course was when Graham explained hygroscopic salt damp. I suddenly released that those darker damp patches on the wall and on internal chimneys masonry were actual hygroscopic salt contamination and not an active leak. The penny dropped!!

Overview

The CSRT course is primarily designed for the remedial timber and damp practitioner, but this should not put off the chartered surveyor, interested in broadening his/her knowledge and understanding.

In order to pass the course I strongly recommend the exam preparation sessions are undertaken, since it provides helpful revision shortly prior to the exams.

The exams are not easy and if you think a bit of study the night before will get you through, think again! This course requires serious revision and the exams require a good deal of stamina. My own private study amounted to some 80 hours and this was on top of a 60 hour week with a young family.

Future development

Due to the cost of the course and the need for a better understanding of dampness, it may be a good idea to develop a standalone course in damp diagnosis. This may encourage more chartered surveyors to gain valuable CPD in dampness and develop a deeper knowledge in this area.

George Dunnett.