Cotswold Stone: Geology, Craft and the Golden Village Landscape

Most English regions are recognised by their landscape. The Cotswolds are recognised by a building material. Walls, roofs, churches, barns, field boundaries and gateposts are made of the same limestone, quarried from beneath the same hills, so that the villages seem to grow out of the ground they stand on. Cotswold stone is more than a pleasing colour: it is a whole system of quarrying, masonry, roofing and repair, and once you understand it, a Cotswold street becomes a document you can read. Two days of our small group tour of England’s villages are spent among these villages, and this article explains what you are looking at.

Where Cotswold stone comes from

The Cotswold hills are made of limestone laid down in the Jurassic period, more than 150 million years ago, when this part of England lay beneath warm, shallow tropical seas. The Cotswolds National Landscape compares the conditions to the seas around Bermuda today. Much of the stone is oolitic: it is built from countless tiny round grains called ooids, each formed as calcium carbonate came out of warm seawater and coated a small particle while waves rolled it back and forth on the sea floor. Look closely at a weathered block and you can sometimes see these grains, like fish roe; the name comes from the Greek word for egg.

Geologists divide the Cotswold limestones into two great groups, the Inferior Oolite and the Great Oolite, laid down at different times and quarried for different purposes. The rocks dip gently eastwards towards Oxford and London, so the hills present a steep scarp to the west, overlooking the Severn Vale, and a long, gentle dip slope to the east. The Cotswolds National Landscape describes the escarpment as the largest continuous landform feature in lowland England. Most Cotswold villages sit on that dip slope, in the sheltered valleys of rivers such as the Windrush, the Coln and the Eye.

Why is Cotswold stone golden in some villages and grey in others?

Because the stone contains different amounts of iron oxide. The Cotswolds National Landscape describes a range from silvery and creamy white, through greys, to golden ochre, depending on how much iron the stone holds. Cotswold District Council’s design code notes a broad pattern across the region: paler creams and greyer tones in the south, deeper creams and honey colours further north. In the far north of West Oxfordshire, ironstones give an orange or ginger-coloured building stone.

The pattern is broad rather than strict, but it is worth watching for as the tour moves from Castle Combe, on the southern edge of the Cotswolds, north to the villages around Bourton-on-the-Water and Stow-on-the-Wold. The colour of a village is a clue to the quarry that supplied it, and many villages built with stone dug close at hand: at Castle Combe, Wiltshire’s community history notes, local quarries have supplied building stone since Roman times.

Quarrying and the reputation of Cotswold freestone

Cotswold limestone has been quarried since Roman times. Historic England’s survey of Gloucestershire’s building stones calls the Cleeve Cloud bed of the Inferior Oolite, also known as Painswick stone, the most widely used and versatile of the Cotswold limestones. It was used by the Romans, and later in great single sections for the fan vaulting of the church of St John the Baptist at Cirencester; the last Painswick quarry closed in 1962.

From the Great Oolite came Taynton stone, quarried in the Windrush valley near Burford and still worked today at Farmington. An Oxoniensia study of the Burford masons traces it in an eleventh-century church tower in Oxford, in Oxford college buildings from 1299, at Windsor Castle and at Eton. Burford’s masons and their stone also travelled to London: Christopher Kempster, one of Christopher Wren’s master masons, supplied stone for St Paul’s Cathedral, and the house he extended at Burford in 1698 still stands. Stone from these hills, in other words, built far more than villages.

The best beds are known as freestone, stone that can be cut and carved freely in any direction. Freshly quarried limestone holds natural moisture known as quarry sap, which makes it easier to work; as the sap evaporates, the stone hardens. Historic England notes that Taynton stone was easy to mould when freshly quarried, which helps explain the crisp carving of so many Cotswold window mullions and doorways.

Masonry: ashlar, rubble and the details that matter

Walk along any Cotswold street and you will see two quite different ways of building in stone. The grander houses, churches and public buildings are often of ashlar: blocks sawn and finely tooled, with flat faces, sharp edges and joints so tight they almost disappear. Most cottages, barns and walls are of rubble, stones roughly squared or used much as they came from the ground, laid in rough courses with wider joints of lime mortar. Many buildings combine the two, with ashlar for the corners, window surrounds and chimneys, and rubble for the walls between.

The details are as characteristic as the stone. Windows are divided by stone mullions, and many are crowned with a projecting hood mould that throws rainwater clear of the window below. Stone is laid as it lay in the ground, with its natural bedding horizontal; set on edge, its layers would be forced apart by frost. Cotswold houses also tend to have narrow gables and shallow plans, a form that sits naturally under steep stone roofs.

The difference between ashlar and rubble is also a record of wealth. A church rebuilt in fine ashlar, or a merchant’s house with a carved doorway, shows where money was spent. In the Cotswolds that money came above all from wool, and our articles on Castle Combe and the making of a Cotswold wool village and on the Cotswold wool churches follow the trade that paid for the finest stonework in the region.

How were Cotswold stone roofs made?

They were made from thin, fissile beds of limestone that could be split into slabs, and in some places the splitting was done by frost. These are not true slates; local craftsmen called them tile-stones. At Stonesfield in Oxfordshire, the source of the most famous Cotswold roofing stone, the Geological Society describes men mining blocks of stone known as pendle in low underground galleries, often only three to five feet high, between Michaelmas and Christmas. The blocks were kept damp under earth to preserve their quarry sap, then uncovered when frost was expected, and the frost split them along their natural layers. A bell was rung to summon the men when a hard frost was due.

Laying the roof was a craft in itself. Stone slates are heavy, a single large one can weigh around 20 kilograms, and they need a steep pitch, typically between about 47 and 55 degrees, to shed water. They are laid in diminishing courses: the largest at the eaves, where they once threw rainwater clear of the walls before gutters were common, and progressively smaller towards the ridge. Cotswold District Council’s roofing guidance records some of the old names for the sizes, from cussoms, the largest at the eaves, through followers, to short cocks near the top; names varied from village to village. Traditionally each slate was hung on the roof timbers with one or two cleft oak pegs.

Today the supply is the problem. Only a handful of quarries produce new stone slates, and they are expensive. Demand for second-hand slates has led, the council warns, to old buildings being stripped of their roofs to supply others. At Collyweston in Northamptonshire, where another famous roofing stone was split by frost, mild winters led Historic England and its partners to experiment with artificial freezing to keep the craft alive.

Dry-stone walls: the stone beyond the village

The same limestone divides the fields. The Cotswolds National Landscape estimates that there are around 6,000 kilometres of dry-stone wall in the region, built without mortar and finished with a coping of stones set on edge. Most of what survives dates from the enclosure of open fields and downland in the eighteenth and nineteenth centuries, though walling here is far older: the Neolithic long barrow at Belas Knap contains some of the earliest known dry-stone work. Many walls are now derelict, and fewer people have the skills to rebuild them. The tour sees a very different walled landscape later in the Yorkshire Dales, explored in our article on Yorkshire’s dry-stone walls.

Weathering, repair and conservation

Cotswold stone ages beautifully, but it needs to be looked after in the right way. The Society for the Protection of Ancient Buildings explains why traditional lime mortar matters: it is softer and more porous than the stone, so moisture leaves the wall through the joints, and the mortar slowly wears away and can be renewed. Hard cement pointing does the opposite. It forces moisture out through the stone itself, where salts and frost then damage the face. West Oxfordshire’s design guide is blunt: cement-rich mortars are not appropriate for limestone, and replacement stone should match the original in size, colour, texture and thickness.

Lichen is part of the look, and its effects are mixed. The British Lichen Society notes that some species can damage stone while others may protect it, and that aggressive cleaning can do more harm than the lichen. Modern building raises its own questions. Cotswold District Council’s design code accepts that reconstituted stone products are common, but notes that they are not the authentic traditional material, do not weather in the same way, and may not be permitted on listed buildings or in sensitive settings. The council expects natural local limestone in the most sensitive places.

How the material shapes a village street

Put all of this together and a Cotswold street begins to make sense. The colour of the walls tells you which quarry was nearby. The contrast between ashlar and rubble shows who had money to spend. The steep roofs and narrow gables are the shape that stone slates demanded. The walls that run from the back gardens into the fields are the same stone again, laid dry. Few English landscapes are so consistent, because few have one material so good, so plentiful and so close at hand.

Arlington Row at Bibury, on the tour’s route into the Cotswolds, shows the system at its simplest. Historic England dates it to the late fourteenth century, when it was built as a wool store, and records its conversion into weavers’ cottages in the late seventeenth century. Its walls are random rubble limestone and its roof is stone slate, and it has been repaired with the same materials ever since.

Where does the tour see Cotswold stone?

The ninth day of the tour enters the Cotswolds through Castle Combe, whose houses are built of Cotswold stone with thick walls and split stone roofs and are listed as ancient monuments, before continuing by way of Cirencester and Bibury to Rodborough. The tenth day is a full excursion to Bourton-on-the-Water and its eighteenth-century bridges, a two-kilometre return walk to Lower Slaughter and its old mill, Lower Oddington’s medieval wall paintings, the market square of Stow-on-the-Wold and the coaching inns of Moreton-in-Marsh. The tour is rated Level 2 (Moderate), with three to five hours of activity a day; village pavements can be narrow and uneven, so comfortable shoes are worth packing.

The Cotswolds are one chapter in a longer story about how England’s villages were built from what lay around them, from Sussex timber and Dorset cob to Dartmoor granite and Yorkshire gritstone. Our guide to the England’s villages itinerary follows that thread from start to finish. If you would like to see the golden villages with someone who can explain how they were made, the England’s villages small group tour is a good way to do it.