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Dry stone, sometimes calleddrystack or, in Scotland,drystane, is a building method by which structures are constructed fromstones without anymortar to bind them together.[1] A certain amount of binding is obtained through the use of carefully selected interlocking stones.
Dry stone construction is best known in the context ofstone walls, traditionally used for the boundaries of fields andchurchyards, or asretaining walls for terracing, but dry stone shelters, houses and other structures also exist. The term tends not to be used for the many historic styles which used precisely-shaped stone, but did not use mortar, for example theGreek temple andInca architecture.
The art of dry stone walling was inscribed in 2018 on theUNESCO representativelist of the intangible cultural heritage of humanity, for dry stone walls in countries such asFrance,Greece,Italy,Slovenia,Croatia,Switzerland andSpain.[2] In 2024,Ireland was added to the list.[3]
Some dry stone wall constructions in north-west Europe have been dated back to theNeolithic Age. InCounty Mayo, Ireland,an entire field system made from dry stone walls, since covered in peat, has been carbon-dated to 3800 BC.[4] These are near contemporary with the, dry stone constructed, neolithic village ofSkara Brae, and theChambered cairn ofScotland.[5]
Thecyclopean walls of theacropolis ofMycenae, Greece, have been dated to 1350 BC and those ofTiryns slightly earlier.[6]Similar example isDaorson, inBosnia,[7] built around a prehistoric central fortified settlement oracropolis (existed there c. 17–16th C. BCE to the end of theBronze Age, c. 9–8th C. BCE), and surrounded bycyclopean walls (similar toMycenae) dated to the 4th C. BCE.[8][9]
InBelize, theMayan ruins atLubaantun illustrate use of dry stone construction in architecture of the 8th and 9th centuries AD.[10]
Great Zimbabwe inZimbabwe, Africa, is an acropolis-like large city complex constructed in dry stone from the 11th to the 15th centuries AD.[11] It is the largest of structures of similar construction throughout the area.[11]
Terminology varies regionally. When used as field boundaries, dry stone structures are more commonly known as dykes inScotland, where professional dry stone wall builders are referred to as 'dykers'. Dry stone walls are characteristic of upland areas ofBritain andIreland where rock outcrops naturally or large stones exist in quantity in the soil. They are especially abundant in the West of Ireland, particularlyConnemara. They may also be found throughout theMediterranean, including retaining walls used for terracing. Such constructions are common where large stones are plentiful (for example, inThe Burren) or conditions are too harsh for hedges capable of retaining livestock to be grown as reliable field boundaries. Many thousands of kilometres of such walls exist, most of them centuries old.
In theUnited States they are common in areas with rocky soils, such asNew England,New York,New Jersey, andPennsylvania. They are a notable characteristic of thebluegrass region of centralKentucky, theOzarks ofArkansas andMissouri, as well asVirginia, where they are usually referred to asrock fences orstone fences, and theNapa Valley in north centralCalifornia. The technique of construction was brought to America primarily byEnglish andScots-Irish immigrants. The technique was also taken toAustralia (principally westernVictoria,[12] some parts ofTasmania, and some parts ofNew South Wales, particularly aroundKiama[13][14]) andNew Zealand (especiallyOtago).
Similar walls also are found in the Swiss–Italian border region, where they are often used to enclose the open space under large natural boulders or outcrops.
The higher-lying rock-rich fields and pastures inBohemia's south-western border range ofŠumava (e.g. around the mountain river of Vydra) are often lined by dry stone walls built offield-stones removed from the arable or cultural land. They serve both as cattle/sheep fences and the lot's borders. Sometimes also the dry stone terracing is apparent, often combined with parts of stonemasonry (house foundations and shed walls) that are held together by a clay and pine needle "composite"mortar.[further explanation needed][clarification needed]
The dry stone walling tradition ofCroatia was added to the UNESCO Representative List of theIntangible Cultural Heritage of Humanity in November 2018, alongside those of Cyprus, France, Greece, Italy, Slovenia, Spain and Switzerland.[2] In Croatia, dry stone walls (suhozidi) were built for a variety of reasons: to clear the earth of stone for crops; to delineate land ownership; or for shelter against thebora wind. Some walls date back to theLiburnian era. Notable examples include the island of Baljenac, which has 23 kilometres (14 mi) of dry stone walls despite being only 14 hectares (35 acres) in area, and the vineyards ofPrimošten.[15]
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InPeru in the 15th century AD, theInca made use of otherwise unusable slopes by building dry stone walls to createterraces. They also employed this mode of construction for freestanding walls. Theirashlar type construction inMachu Picchu uses the classicInca architectural style of polished dry stone walls of regular shape. The Incas were masters of this technique, in which blocks of stone are cut to fit together tightly without mortar. Many junctions are so perfect that not even a knife fits between the stones. The structures have persisted in the high earthquake region because of the flexibility of the walls, and because in their double wall architecture, the two portions of the walls incline into each other.
The style and method of construction of a wall will vary, depending on the type of stone available, its intended use and local tradition. Many older walls were constructed from stones andboulders cleared from the fields during preparation for agriculture[16] (field stones) although some used stone quarried nearby. For modern walls, quarried stone is almost always used.
One type of wall is called a "double" wall and is constructed by placing two rows of stones along the boundary to be walled. The foundation stones are ideally set into the ground so as to rest firmly on thesubsoil. The rows are composed of large flattish stones, diminishing in size as the wall rises. Smaller stones may be used as chocks in areas where the natural stone shape is more rounded. The walls are built up to the desired height layer-by-layer (course by course) and, at intervals, largetie-stones orthrough stones are placed which span both faces of the wall and sometimes protrude. These have the effect of bonding what would otherwise be two thin walls leaning against each other, greatly increasing the strength of the wall. Diminishing the width of the wall as it gets higher, as traditionally done in Britain, also strengthens the wall considerably. The voids between the facing stones are carefully packed with smaller stones (filling,hearting).
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The final layer on the top of the wall also consists of large stones, calledcapstones,coping stones orcopes. As with the tie stones, the capstones span the entire width of the wall and prevent it breaking apart. In some areas, such as South Wales, there is a tradition of placing the coping stones on a final layer of flat stones slightly wider than the top of the wall proper (coverbands).
In addition to gates, a wall may contain smaller purposely built gaps for the passage or control of wildlife andlivestock such as sheep. The smaller holes usually no more than 200 millimetres (8 in) in height are called "Bolt Holes" or "Smoots". Larger ones may be between 450 and 600 mm (18 and 24 in) in height, which are called "Cripple Holes".[17]
Boulder walls are a type of single wall in which the wall consists primarily of large boulders, around which smaller stones are placed. Single walls work best with large, flatter stones. Ideally, the largest stones are being placed at the bottom and the whole wall tapers toward the top. Sometimes a row of capstones completes the top of a wall, with the long rectangular side of eachcapstone perpendicular to the wall alignment.
Galloway dykes consist of a base of double-wall construction or larger boulders with single-wall construction above. They appear to be rickety, with many holes, which deters livestock (and people) from attempting to cross them. These dykes are principally found in locations with exceptionally high winds, where a solid wall might be at risk of being unsettled by the buffeting. The porous nature of the wall significantly reduces wind force but takes greater skill to construct. They are also found in grazing areas where they are used to maximize the utility of the available stones (where ploughing was not turning up ever more stones).
Another variation is theCornish hedge or Welshclawdd, which is a stone-clad earth bank topped by turf, scrub, or trees and characterised by a strict inward-curvedbatter (the slope of the "hedge"). As with many other varieties of wall, the height is the same as the width of the base, and the top is half the base width.
Different regions have made minor modifications to the general method of construction—sometimes because of limitations of building material available, but also to create a look that is distinctive for that area. Whichever method is used to build a dry stone wall, considerable skill is required. Correcting any mistakes invariably means disassembling down to the level of the error. Selection of the correct stone for every position in the wall makes an enormous difference to the lifetime of the finished product, and a skilled waller will take time making the selection.
As with many older crafts, skilled wallers, today, are few in number. With the advent of modern wire fencing, fields can be fenced with much less time and expense using wire than using stone walls; however, the initial expense of building dykes is offset by their sturdiness and consequent long, low-maintenance lifetimes. As a result of the increasing appreciation of the landscape and heritage value of dry stone walls, wallers remain in demand, as do the walls themselves. A nationally recognised certification scheme is operated in the UK by the Dry Stone Walling Association, with four grades from Initial to Master Craftsman.
Notable examples include theMourne Wall, a 22-mile (35 km) wall in theMourne Mountains inCounty Down,Northern Ireland, and the wall around theOttenby nature reserve, built byCharles X Gustav in the mid-17th century inÖland, Sweden.
While the dry stone technique is most commonly used for the construction of double-wall stone walls and single-wall retaining terracing, dry stone sculptures, buildings, fortifications, bridges, and other structures also exist.
Traditional turf-roofed Highlandblackhouses were constructed using the double-wall dry stone method. When buildings are constructed using this method, the middle of the wall is generally filled with earth or sand in order to eliminate draughts. During the Iron Age, and perhaps earlier, the technique also was used to build fortifications such as the walls ofEketorp Castle (Öland,Sweden),Maiden Castle, North Yorkshire,Reeth,Dunlough Castle in southwest Ireland and the rampart of the Long Scar Dyke. Many of the dry-stone walls that exist today in Scotland can be dated to the 14th century or earlier when they were built to divide fields and retain livestock. Some extremely well built examples are found on the lands ofMuchalls Castle.
Dry stone walls can be built against embankments or even vertical terraces. If they are subjected to lateral earth pressure, they are retaining walls of the type gravity wall. The weight of the stones resists the pressure from the retained soil, including any surcharges, and the friction between the stones causes most of them to act as if they were a monolithic gravity wall of the same weight. Dry stone retaining walls were once built in great numbers for agricultural terracing and also to carry paths, roads and railways. Although dry stone is seldom used for these purposes today, a great many are still in use and maintained. New ones are often built in gardens and nature conservation areas. Dry stone retaining structures continue to be a subject of research.[18]
In northeasternSomalia, on the coastal plain 20 km (12 mi) toAluula's east are found ruins of an ancient monument in a platform style. The structure is formed by a rectangular dry stone wall that is low in height; the space in between is filled with rubble and manually covered with small stones. Relatively large standing stones are also positioned on the edifice's corners. Near the platform are graves, which are outlined in stones. Measuring 24 by 17 m (79 by 56 ft), the structure is the largest of a string of ancient platform and enclosed platform monuments exclusive to far northeastern Somalia.[19]
In Great Britain, Ireland, France and Switzerland, it is possible to find small dry stone structures built as signs, marking mountain paths or boundaries of owned land. In many countries,cairns, as they are called in Scotland, are used as road and mountaintop markers.
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