Early dry stone structures of Malta

Before the advent of mortars, all stonemasonry utilized drystone techniques. The oldest examples of this style of construction that still stand are the megalithic stone temples of Malta, the earliest dating from 4000 B.C., predating both the Pyramids and Stonehenge. The Stone temples of Malta utilized post and lintel construction, as well ingeniously corbelled stone which allowed half domes to be constructed, which were then covered with timber and animal hide. The temples typically featured an imposing entrance, from which one proceeded to a more intimate grouping of hemispherical apses, often arranged in a cloverleaf (tri-foil) pattern. Little is known of the people from this period, but the sheer size of the stones utilized implies a concerted effort from the populace, utilizing techniques lost to history, probably not unlike those used at Stonehenge (Gunther 1).

Stone walls of the Inca

Another interesting example of early drystone technique is provided by the Inca from fifteenth century Peru. The Inca utilized an Ashlar-type stone to build terraces and freestanding walls of astonishing workmanship. In many cases, the blocks are cut so perfectly it is impossible to slide even a knife between the individual stones.  The freestanding walls built by the Inca utilized a double wall architecture, where the exterior portions of each wall lean into each other in what’s called a ‘batter’. This same method was utilized by drystone masons throughout the middle-ages and is still used to this day (among other techniques) to impart greater strength to drystone structures. Of special note however, is the use by the Inca of oddly shaped, often trapezoidal stones arranged in a jigsaw-puzzle like fashion.  These stones allowed the walls built by the Inca to absorb and withstand the lateral and vertical stresses of the powerful earthquakes of the region, and then return to their original position as the earthquakes subsided  (Wikipedia, Incan architecture ).

With the advent of the first lime mortars in Egypt, followed later by the invention of hydraulic cements in ancient Greece and Rome, drystone masonry began to play less of a role in the construction of dwellings and other structures, and found greater use in its modern role as an agricultural enclosure. This shift in use did not occur overnight however, given that the technology of hydraulic mortars and cement (which had been perfected by the Romans) was then lost for nearly two millenia during the Middle Ages, where we see cathedrals and fortifications constructed with only simple lime mortars. Given that lime mortar can be degraded by contact with water, many of these structures have been damaged by wind blown rain over the centuries (Wikipedia, Mortar(masonry)). Thus even in the Middle Ages, we still find occasional fortifications, bridges, dams, kilns and other structures utilizing drystone techniques, where these had been all but abandoned in Roman times. Ultimately however, drystone masonry assumed the role as the method of choice for the agricultural enclosure, and we will see a profusion of styles, terminology, and construction methods over the centuries.

Any discussion of drystone walls requires a bit of understanding of the terminology used, as this varies from region to region, as well as an understanding of basic engineering involved.  Most simply, a dry stone wall (also known as a dyke in Scotland, or a stone fence in parts of the U.S.)  is any wall that is constructed without the use of mortar to bind the stones together; instead the wall is bound together by the weight of the stones, and, hopefully, by the careful selection and interlocking of stone on the part of the mason.  Most commonly dry stone walls were created by a farmer who was clearing a field in order to grow crops, and who subsequently added to the wall in following years as frost-heaving brought new stone to the surface of the farmer’s field. This type of dry stone wall is typically called a tossed wall, or dry-stack wall, and may often be a somewhat haphazard construction, as the first stones unearthed by the farmers were often very hard, rounded glacial till that were very difficult to work with and resulted in the rubbly ‘tumble-down’ appearance we find in the older stone walls of New England. When stones are more carefully placed in double walled design, and filled in the middle with rubble, the wall is usually referred to as a dry-laid wall, and one will find these constructed by farmers with greater masonry experience, or by masons in the form of ‘fancy’ or ‘estate’ walls; walls surrounding private residences of wealthier farmers and homeowners that have little purpose (beyond aesthestic). These terms are somewhat interchangeable however, and shouldn’t be too relied on to classify a wall, as ultimately the structure and design of a dry stone wall is determined by the kind of stone available and the aesthetic choices of the mason, though, as we will see below, there are certain ‘best-practices’ in drystone masonry which can result in a wall that will last centuries.

Wall cross-section credit:DCS- Dry Stone Conservancy

Naturally, drystone walls were also constructed as barriers for livestock, and in this use we find many of the characteristics that make up a durable stone wall that will stand the test of time.  To begin, a drystone wall does not typically require a deep foundation as is required with other masonry work, as the wall is able to bend and flex with the movement of the earth during periods of warmth and frost (though a foundation below the frostline will certainly add to the life of the wall). Typically only the topsoil is removed, and a course of heavy foundation stones is laid. The foundation course is typically laid wider than subsequent courses as this provides more support should any stone shift outwards over time. Following this stones are laid in the time honored ‘one over two, two over one’pattern ensuring that each joint, or break between stones, is crossed. Individual stones are selected for the best looking face, and laid so that the angle of the face of the stone matches the overall batter, or slant of the wall. The center of the wall, or ‘hearting’ is packed with rubble or unattractive stones that aren’t useful for the face of the wall. The packing of the wall is an integral part of it’s structure, and as each face stone is placed, packing is also placed underneath and behind the stone to ensure many points of contact with adjacent stones. A good mason will typically strive to use the largest stones that can fit in the available space between the two faces of the wall, as larger stones will break down more slowly than smaller, increasing the lifespan of the wall. Packing from behind each stone, instead of chinking from the front, ensures that stones don’t fall out, weaking the wall, but also ensures that as the smaller ‘hearting’ stones break down over time, the wall will settle into itself, actually becoming stronger. You will see in the provided picture a course of tie-rocks (also called through-stones) laid halfway up the height of the wall- these are longer stones that extend the full width of the wall, and are placed around every three feet along the length of the wall. These stones serve to tie the two faces of the wall together, providing additional structural support, and ideally will stick out an inch or two from the face of the wall, which helps resist settling in a fashion similar to the wider foundation stones. Sometimes throughstones do not protrude as the does the foundation, which may be an aesthetic choice made by the mason, but this does reduce the lifespan of the wall. At the top of the wall you find a cover course of heavier stones that extend the width of the wall, and on top of this you might find a decorative (and functional) coping (a row of stones placed in a vertical or diagonal fashion). The use of a coping is more common in the U.K. and only typically found in the U.S. in communities that were once very English, such as Newport, Rhode Island.

One of the interesting aspects of a drystone wall is its resistance to the effects of water. Rain water can simply drain right through a drystone wall, and wind can pass through the sides, drying it out, whereas in a mortared wall water can infiltrate the cracks in the mortar, and freeze/thaw cycling will eventually cause the joints in the mortar to fail. As a result, drystone walls can frequently outlast mortared walls, and indeed there are well built drystone walls in the U.K. thought to date to the fourteenth century and earlier (Wikipedia, Dry Stone). That said, a drystone wall is not immune to water, and the aforementioned cover course serves two purposes, one is to add additional wieght (and strength) to the wall, and the second is to protect the top of the wall from leaf litter and other debris accumulating inside the top of the wall. Over may years, this material breaks down into dirt, which can absorb water, making the wall slightly subject to the freezing and thawing that plagues mortared walls.

'Fallen Soldiers' coping

The coping on top of a drystone wall typically consists of stones that have no proper flat surfaces that one might want to use in the face of the wall, and so is a good way to make use of what might otherwise be considered waste rock. The coping also adds weight to the top of the wall, and serves the second purpose of protecting the wall from large livestock who might attempt to browse for forage by reaching their necks over the wall. The sharper and often irregular shapes of coping stones make this too uncomfortable and helps to prevent these hefty beasts from shiftng the stones near the top of the wall which have less support than those below.

We find a number of additional design features in drystone walls as well: Stiles were frequently built to allow people to cross a wall and while keeping livestock contained-

A step style with gap to pass through

A dry stone Gap Stile

A Hoghole, Slip, or Sheep Creep is a small hole in a wall created to allow the passage of younger sheep or hogs while preventing the passage of adults:

A 'Hog Hole' or 'Sheep Creep'

Even smaller holes called Smoots were created to allow the passage of badgers and rabbits, discouraging them from digging under (and undermining) the wall:

Dry stone 'Smoot'

Here we see square recesses for beehives called Beeboles: (Fellsanddells.org, Drystone Walls).

'Bee Boles' for some lucky bees!

One can see how these features might still have a use in a modern landscape. A Step Stile might be used as a series of ledges for planters, whereas a Beebole might be used to frame a plant or garden ornament.

From an aesthetic standpoint, it’s often considered a good practice to use stone native to a particular region. This is why certain types of stonework seem to ‘fit’ within a landscape, while others seem to have no business being in a particular landscape. A wall made of red sandstone located in an area where there is no native sandstone just doesn’t seem to work. However some flexibility exists. In the Washington D.C. metropolitan area for example, the local stone is a mica shist, and works naturally within the landscape. However other stones, such as a Pennsylvania fieldstone, or a Shenandoah stone will work equally as well as they are native to the overall Mid-Atlantic region. Similarly the style of a stone wall is often dictated by the types of stone available in the area, and we will see that drystone walls can often have quite a bit of regional character:

A dry stone wall built of slate

This wall combines slate & river cobbles

Big enough stones allow for a 'Standing Stone' wall

Dry laid wall of Cotswold limestone

A diagonally-laid wall in Dorset

A Herringbone pattern wall

Frequently stones were laid into earthen banks to form hedges such as those for which Cornwall is famous:

Stone hedge in Cornwall

Vertical stone wall in Cumbria

A Scottish boulder dyke

A fieldstone wall in Kentucky

A 'lace' wall in Connecticut

A civil war era wall in Virginia

In America, drystone walls are often attributed to the colonial period, and are seen as representative of the hard labors endured by the Puritans as they hacked an existence out of the wilderness. However, as the countryside was slowly cleared, wood was in abundance, and this wood was made use of for fences. The early settlers were also accustomed to working land in common, and formed small villages with common fields on the outskirts. This was done in part because this was what they were familiar with, and also because the threat of Indian hostilities made many fearful to venture out past the protection of the settlements. It was not until these Indian threats were ‘contained’, and “the New World’s great abundance of land began to change the colonial mindset, that the system of common fields came to be seen as a waste of both time and land, and farms were established as the cohesive isolated units we know them as today.” (Allport 32). Additionally, early settlements were frequently located near estuaries, with a sufficiently thick layer of alluvial soil for farming, and it wasn’t until settlers moved out into surrounding rocky uplands that a large amount of rock needed to be cleared (Thorson 77). The early Americans also used large amounts wood for structures, fences, and most importantly for fuel, and as the colonies expanded, the rapid development led to it’s diminished availability.

Lastly an increased interest in the raising of sheep towards the end of the 18th century caused an increased need for pasture fencing, for which wood was [becoming] scarce. Thus the stage was set during the Revolutionary period for a boom in drystone wall construction, and “millions of stone walls were built after the beginning of the American Revolution between 1775 and 1825” (Thorson 104).

Interestingly, some  sixty percent the wood fences in the 1800’s were built in the split-rail, zig-zag (or ‘worm’) style that did not require any fence posts, (as often the soil was too rocky to drive posts into) and we even find some early drystone walls built in a zig-zag pattern as well. This wouldn’t appear to make much sense at first, until we realize that the early farmers were actually throwing stone along their zig-zag wood fence as they cleared their fields, and after many years this collected into a wall with a very distinctive pattern (Allport 43).

As the farmers cleared their fields each spring, they tossed the frost-heaved stone next to their original wood fence, until there was so much stone that they needed to stack it to maximize the amount of arable land.  Since additional stone seemed to magically reappear each year, the farmers must have wondered where all this new stone came from. Some naturally declared it to be the work of the Devil, and others swore that the stone grew from seed, as in an old New England maxim: “Maine’s number-two crop is potatoes, Its number-one crop is stones” (Allport 59).

The new surge in stone wall construction, combined with the increase in sheep-farming, led to a need to create stone walls of greater quality. Sheep are nimble animals, and only a high, steeply faced wall can contain them. However, a steeply faced wall is unstable unless properly built, and this led to a greater development of the craft of dry stone masonry in the New World. As old farms were converted into sheep-pasture, farmers rebuilt the old tossed stone walls into more stout ‘dry-laid’ walls capable of containing the sheep. Another method, if wood was available, was to drive wooden stakes at an angle on either side of the old wall, forming an ‘x’ shape above the wall, on which a wooden rail was laid. These ‘stakes and riders’ formed a picturesque half-stone, half-wood fence:

A 'Stakes and Riders' fence

Often however, the ground would be so rocky that a zig-zag fence, or a drystone wall would be the only option.

“At the same time that New England farmers were beginning to convert their wheat fields to sheep pastures, a development was taking place in the towns of New England that would eventually transform the nature of farming in the region, as well as contribute to the 19^th century wall building boom. This was the growth of manufacturing. Or, rather, not so much the growth of manufacturing itself, but the growth of an industrial or manufacturing population- a population that needed the goods that farmers produced” (Allport 96).  The new demand for agricultural products led to progress and differentiation in farming, as well as increased wealth. Farmers were able to improve their stock, renew depleted soils, and rebuild their fences. “Most of the publications of the period advised their readers to replace their ‘half-rotted, worm eaten’ fences with stone walls and that when building those walls, they should spend the time and money to build them well”  (Allport 99).  In 1842, The Cultivator reminded farmers that “good fences prevent eructations of bile among neighbors, contribute much to the good appearance of the farm, prevent the destruction of crops, and check in the bud that disposition to live at large which exists in most animals” (Allport 99).

The walls that received the most energy on the part of the builders were those that surrounded their farmyards, garden plots, town pounds, (a storage place for livestock) and cemeteries. These would often receive a proper foundation, and be carefully laid. Many of these still survive today.

Ironically, contained within the industrial revolution and the agricultural improvements of the 19^th century were also the seeds of the demise of the drystone wall. “The family farm came to be seen less as a home to be lived in than as an exploitable resource to be managed for personal gain. This ideological shift coincided with the realization that the larger, stone-free fields of the praries would yield a higher profit, given the transportation improvements that were taking place. Economic incentive rather than individual liberty and self-sufficiency became the guiding principle of land use.” (Thorson 154) After the Erie Canal opened, farmers began to move west to take advantage of the wide rock-free expanses, and the exodus reached great proportions when by 1850, one half of native born Vermonters had moved West. (Allport 142).

Western farmers were able to make use of new farming technologies such as the horse drawn  “McCormick reaper, horse rakes, and seed drills, and the very great irony of the stone walls of new England is that they helped to make the use of these fast and cumbersome machines impossible“ (Allport 142). Eastern farmers were quickly unable to compete with western farmers, who were able to farm on a scale impossible in the East.  Another great disincentive to remaining on the old New England farms came with the Homestead Act of 1862, which gave away vast amounts of land with rich soil, and made the small scale farming of the East a losing proposition. The final death knell of the agricultural drystone wall came when livestock farmers were also lured West by the invention and manufacture of wire fencing, which came into wide use after 1874, and meant that there was no need to maintain the drystone old walls. Vast tracts of land in the West could be enclosed in short order. To be sure it is much easier to string up barbed wire than handle the tons of stone required to build a stone fence  (Thorson 169).

No stone wall can last forever, and the best rarely have life spans exceeding 200-300 years.  As the farms were abandoned, trees grew in the previously cleared fields, and subsequently fell on the old walls, breaking them apart.  Freezing, thawing and erosion all did their part to weaken and undermine the walls.  Walls built on slopes faced the inexorable pressures of soil creep, as soil slowly flowed downhill and gradually pushed walls apart. Drystone walls also found themselves ready quarries for those who needed stones for construction, and most recently, have suffered the indignity of unscrupulous stone dealers, who harvest the old walls because the lichen covered ‘weatherface’ stones can be sold at a premium to those who desire stone with an instantly aged appearance.

Interestingly, one can (roughly) date a stone wall by the lichen on it’s faces. A wall of ten years or so will have just a few colonies of lichens, whereas an older wall may be nearly covered.  Some lichens, such as Crustose lichens grow l millimeter per year or less, so a Crustose lichen with a radius of 3 centimeters would indicate the lichen had been living on the rock at least 30 years (Allport 183). There is no need to harvest these old walls, however, if aged stone is the aesthetic one is looking for.  Lichen covered rocks can routinely be found on the scree slopes of mountains, and in this author’s experience, stone walls will grow mosses in very short order. I have seen stone walls turn green with baby mosses in as little as six months after construction, given the right conditions.

An engineer in 1939 used federal agriculture records to estimate that just after the Civil War, there were approximately 240,000 miles of stone walls in New England.  It would be impossible to guess what remain today, but certainly far less, which make those that remain all the more deserving of restoration. Organizations such as the Drystone Conservancy in Kentucky, and similar organizations abroad, do great work in the preservation of old drystone structures, and more importantly, in perpetuating the craft of drystone masonry.

Having studied at the Conservancy, and worked with large quantities of stone, I  can speak to the rigors involved in drystone masonry, but also to the pleasure gained from the simplicity and honesty of the work. Stone walls can humbly impart a sense of time, history, and place, and the knowledge that one’s work may be appreciated for generations is truly gratifying.  In a time where homes are built with rapid building systems, and designed to last for two generations at best,  “The old stone walls stand guard against a future that seems to be coming too quickly. They urge us to slow down and recall the past” (Thorson 232)  as well as serve to remind us “that all history is paradoxically as eternal, and ephemeral, as a simple stone wall.”(Thorson 232)

Works Cited:
Thorson, Robert M. Stone by Stone, The  Magnificent History in New Englands Stone Walls. New York: Walker & Company, 2002.

Allport, Susan. Sermons In Stone, The Stone Walls of New England and New York. New York: W.W.Norton & Company, 2002.

Gunther, Michael. “Prehistoric Temples of Malta” Art-and-archeaology.com. 1998. 13 April 2008 <http://www.art-and-archaeology.com/malta/malta.html>.

“Incan Architecture.” Wikipedia: The Free Encyclopedia. 13 April 2008, <http://en.wikipedia.org/wiki/Incan_architecture>.

“Mortar(Masonry).” Wikipedia: The Free Encyclopedia. 13 April 2008, <http://en.wikipedia.org/wiki/Mortar_(masonry)>.

Source: Connect to history with Dry Stone Walls - Sisson Landscapes