One of the most striking features of the British landscape is the unending file of dry stone walls criss-crossing our upland, pastures and ascending moor land and fell. Many have stood for hundreds of years, buffeted and scarred by an unyielding barrage of rain, wind and snow - still standing proud and strong to this day. Monuments made from simple architectural techniques. An accolade to those craftsmen who struggled to climb the steepest incline carrying stone and tools. Braving the elements day in, day out.

The actual art of dry stone walling dates back thousands of years and the Celts were absolute masters of the craft. Evidence of their skill can still be seen today with their intricately constructed Cells within the British Isles. Perhaps the most striking element of this skill is that the technique has not really changed and the walls constructed today employ the very same principles used by those ancient tribes.

When the landscape was initially populated more than 4,000 years ago, the tribes were hunter-gatherers and did not practice agriculture. Most of the remains of their architecture have revealed to historians that their dry stone buildings were used for dwellings and ceremonial purposes. There are many Stone Age examples of the use of dry stone construction, hut circles in Dartmoor, and burial mounds in the North and South Downs are some of the best.

Later tribes built barrows and cairns, many of these can be seen on the upland areas of Britain. Iron Age Celts built homes using natural stone; some agricultural enclosures were constructed at this time. In the far North of Scotland, on the Isles of Hebrides and Orkney, there are examples of villages constructed from natural stones. One of the most striking features are the “Brochs”, possibly used for ceremonial purposes, these are tall cylindrical towers built of dry stones.

The greatest changes in agricultural practices took place around 900AD. During this period, populations became more settled and farming became the predominant activity. The system of agriculture in use was the ‘Open Field System’, crops were grown in strips of land in a large field and animals were grazed on commons. Farming practices did not change significantly until the 14th Century.

The craft of dry stone walling, as we know it today, owes much to the Scottish Drystane Dykers who probably mastered the art to blend in with the British farming system. Many of Britain’s field walls were built between 1500-1900. The greatest time of construction would have been between 1760 and 1845 during the ‘Enclosures Act’. The long walls stretching over the hills of upland Britain are our most recent – having been commissioned by the landowners and estates to mark the boundaries of the areas which they had claimed for themselves.

Those walls forming very small enclosures often found winding their way unevenly around homesteads are some of the oldest and were built, it is thought, to retain animals of subsistence farming. Families farming the harsh uplands built many of these before the Enclosures Act, but some were constructed during the Act in an attempt to claim the land for themselves. The larger landowners were more intent on requiring more fertile, valuable areas of lowland Britain.

Although in lower areas the Enclosures Act led to the introduction of hedges and fences, in the wilder remote uplands it was difficult to establish other methods of marking boundaries. The abundance of rocks and stone littering steep hillsides were utilised instead. Instead of following the contours of a hillside, the walls were erected from valley base to summit and beyond.

Nowadays, to the untrained eye, they seem to be held in place by some incredibly strong invisible force.

The varied appearances and styles of this type of construction are down to the inherent differences in the availability and properties of the locally found stone. The landscape of Great Britain is incredibly varied, often changing completely within a few miles. The reason for these dramatic transformations lies beneath the surface of the soil, in the large number of different types of bedrock. Individual rock types have varying properties, which leads to different patterns of erosion. This island has seen massive geological upheaval in the distant past, leading to rock types of different age and constituents surfacing side by side despite being formed millions of years apart.

There are three divergent rock types, igneous, sedimentary and metamorphic. Igneous rocks are formed when hot molten rock cools down and solidifies. They appear in two forms. Intrusive and extrusive. Intrusive rocks cool below the surface and extrusive rock cools above ground. Granite is an example of an igneous rock. As they tend to be crystalline, igneous rocks are very hard and difficult to break and form areas of high ground. Whilst this property makes stone resistant to erosion, it has the disadvantage of leaving it very difficult to dress to shape using walling tools.

Sedimentary rock is formed when particles of material are laid down and subsequently compressed. The particles can arise as a result of erosion of pre-existing rock or from organic matter such as shells or bones from animals. There are many differing rocks of this type, but the two examples that are widely used by dry stone wallers are sandstone and limestone. Sandstone arises from compressed sand particles and shale, but originally derived from compressed mud. Limestone is made from the bodies of sea creatures and is predominantly calcium carbonate. Chalk is also predominantly calcium carbonate but is a much softer rock than limestone.

Sedimentary rock is laid down in bedding planes, and as such is easy to split along these planes. Whilst this leads to the rock being more resistant to erosion, it makes it ideal for the experienced dry stone wall builder to dress and use. Stone of this type tends to have good “faces”, which again makes it ideal for walling.

The third type of rock is metamorphic. This rock is formed when existing rock (either sedimentary or igneous) is subjected to immense heat or pressure, or a combination of both. These conditions could have occurred at times when volcanic activity or earth movements were prevalent. Since most types of metamorphosed rock tend to be valuable, like marble, they are not likely to have been used for dry stone walling. However one type of metamorphic rock is extremely common in Great Britain and that is slate.

Slate was formed when shale was subjected to volcanic activity, and is prevalent in upland areas, particularly in Wales, Cornwall and parts of the Lake District. Slate is an easy to use stone for dry stone walling, hosting a number of useful properties include cleavage, this is where it is easy for a skilled person to break slate along the original bedding planes of the shale.

The natural lifespan and demise of a dry stone wall is dependant on erosion and all three rock types are subject to this. Erosion is predominant in two forms, chemical and mechanical. Chemical erosion occurs when the actual constituents of the rock are dissolved by acid. This is called ‘chemical weathering’. Weathering takes place when carbon dioxide in the air combines with rainwater and falls to earth as acid-rain. The damage is caused when the rain penetrates the stone. All rock types are susceptable to this action, however the harder rocks such as granite take millions of years to be eroded in this way. If acidic minerals are present the process can be speeded up. Limestone, chalk and slate have become more vulnerable since the advent of pollution.

Mechanical erosion occurs when natural variation in temperature causes the rock to expand and contract. This action results in large pieces breaking free from the main structure. The process is exacerbated when water penetrates along natural fault lines then freezes. Eventually this results in the formation of piles of boulders being formed in exposed rocky areas. This would have been one of the original sources of material for upland farmers to use for construction. Other sources included quarries, specifically excavated for enclosure purposes and nearby river beds where walling stone was extracted.

Many of the contrasts in styles of walling throughout the British Isles arise from differences in the properties and availablity of local rock. As outlined earlier, there are many different bedrock types, all of which are millions of years old. An interesting thought for today’s wallers, when they pick up a stone to add it to a new structure, is that the material could have been formed even before the dinosaurs roamed the Earth.

The oldest rocks are the Pre-cambrian, which form some of the ancient sandstones of upland Wales and Southern Scotland. The bedrock in these regions was formed 3400 million years ago, before life began.

Later volcanic activity pushed up mountain ranges and created igneous and metamorphic rocks; this included regions of granite in Dartmoor and the Lake District. The mountains in these regions are made of very hard rocks that have resisted erosion. Large slabs of granite were used to build a dry stone drovers bridge in Dartmoor, the structure is still in use today as a footbridge. At Grimspound, in Devon there is a Bronze Age settlement which is completely surrounded by a dry stone wall made entirely of granite.

Following this period of upheaval, these islands became a desert. During this period the old red sand stones were formed. This excellent building stone is predominant in Devon (hence the name Devon Red sandstone), and forms a band up the west of Britain through the West Midlands, Shrewsbury, Chester and up to the North West of Cumbria.

In the dark peak area of the Peak District National Park, a similar type of stone is present, known locally as Derbyshire Gritstone. In areas where this stone was present close to the surface, there are ample examples of ancient dry stone structures made from this distinctive material. Sandstone, no matter what form it presents itself, is easy to dress to size and shape – hence the beautiful, smooth faces usually associated with this style of wall.

During the Carboniferous Period (between 345 million and 320 million years ago) Britain was covered with warm seas. Within this period limestone was formed by the compression of the remains of sea creatures. The presence of carboniferous limestone in this country has led to the formation of the distinctive landscapes of the Yorkshire Dales and the White Peak in the Peak District National Park.

In these upland areas the construction of dry stone walls came into its own. The abundance of exposed areas of rock and availablity of piles of stone provided the ideal material for the hill farmers to construct stock proof barriers. One of the great delights of walling with this type of limestone is the presence of fossils. If the waller is not careful, it’s possible to spend more time painstakingly chipping away with the walling hammer to extract the specimens, than on the job in hand!

A different type of limestone was formed later, during the Jurassic Period (around 195 million years ago). This limestone forms a ridge from Dorset through to the Cotswolds, and there is second ridge which finishes in the North York Moors. In the Cotswolds there are many fine examples of dry stone walls constructed from this limestone. This type of limestone is harder than the Carboneferous limestone, and is not so easy to wall with. The problem is mainly due to its small size and the lack of ideal stone to tie the walls together. It is for this reason that the Cotswolds walls are lower in height than any other region.

Chalk is a very soft rock, and is present in Southern England and forms the bedrock of the North and South Downs. There is also an area of chalk in the east, this is the bedrock that resulted in the formation of the Yorkshire Wolds. Chalk contains bands of fossilised remains resulting in bands of darker flints.

Although chalk has not been used extensively to form dry stone walls as stock barriers, ancient tribes used it to construct buildings. Some of these structures remain today, evidence of the durability of this construction method.

The newest type of rock in the British Isles was formed during a second period of volcanic activity as recently as one million years ago. During this time period the granites of the North of Scotland were formed. Dolerite was also formed in West Wales. This is the material used to build Stone Henge and there are examples of dry stone buildings made from this material in West Wales.

The origins of this rural craft are firmly rooted in the past, reaching back to a time before life as we know it began. The styles, shapes and appearances of dry stone walls are intertwined with the landscape and heritage of an area in a way that no other man made structure ever can. The practitioner of this ancient art can be assured that, as he or she places each stone into a dry stone wall, the act entwines a piece of history into a natural landscape. A human touch in complete harmony with nature, enhancing the appearance and conservation value of the countryside. There are not many building techniques in use today that can boast these kind of advantages!

Many of us, at some stage, have looked upon these ancient structures, wondering how have they managed to survive the onslaught of the years. With no cement to keep them together, why don’t they fall down?

Like most things in life, however, nothing withstands the passing of time without some element of decay. Theft, livestock pushing against well built layers, people taking short cuts across fields, climbing walls and dislodging top stones, can all lead to a wall’s demise. Urban sprawl has played its part also, as has the unfortunate demise of the farming community. Thankfully within our National Parks and conservation areas a program of preservation is in place and there are plenty of opportunities for anyone wishing to take up the craft.