'Good shoes and a hat' style

The North Wessex Downs form the largest designated Area of Outstanding Natural Beauty in southern England, a broad expanse of chalk upland through South Oxfordshire, West Berkshire, Wiltshire and North Hampshire.

The Downs covers 1,730 sq km and was created in 1972 to protect one of the largest tracts of chalk downland in southern England. The AONB celebrates the area's rich diversity of archaeology, ecology, landscape and culture for everyone to enjoy.

The natural beauty is enhanced by the picturesque villages and towns, whose buildings, typically using local materials, vary in style from one location to another.

This variation can be linked to changes in the underlying geology. In past centuries the transport of heavy building stone was expensive and local masons used what was close at hand. Sometimes this was chalk or flint, sometimes sarsen stones and sometimes clay for brick and tile-making, although bricks were also expensive.

Builders evolved styles which used these materials in combination. Only where extra strength or versatility was needed was building stone such as Cotswold limestone brought in from further afield, which was costly and considered only for the more prestigious buildings.

Upper, Middle and Lower Chalk underlies most of the region. Generally, the chalk is too soft, porous and friable to be used as a building stone. However, it is used as a building stone along the northern edge of the region where, historically, chalk block was quarried.

The use of flint matches well the distribution of Upper Chalk. This pure, soft, white chalk locally contains thin bands of flint which weather easily and are found scattered in fields across the Downs.

Chalk block cottages have resisted the weather for centuries by having "good shoes and a hat", that is a plinth of stone or brick to stop rising damp and overhanging eaves of thatch to resist the weather.

Lime-washed cob walls at Blewbury are protected from the weather by a thatch capping and from rising damp by a stone base. Cob is an ingredient of wattle and daub and is compacted to form broad boundary walls with the rounded outlines.

A more ambitious chalk block building is Ashdown House in Upper Lambourn. But here stronger limestone has been used for the corner stones, window frames and balustrades.

Sarsen stone has been used for building in the west of the region, close to areas where surviving scatters of sarsen stones can be found in the landscape such as near Ashdown House.

Sarsen stone has resisted weathering for thousands of years. It has been used as a building stone since Neolithic times, the best known example in the region being the megalithic monuments at Avebury.

However, sarsen stones have also been used over the centuries for domestic buildings and walling. By the mid-19th century, a sarsen-cutting industry was flourishing in this area and sarsen stone was being cut into regular blocks suitable for walls, corner stones and paving.

Brick is the dominant material used across the region. Houses built solely of brick with clay roof tiles dominate the clay areas. However, in areas where chalk, sarsen and flint building materials are available, brick has been used for framing and strengthening these materials.

The clays were dug extensively for brick making, especially around Inkpen, Kintbury and Hermitage.

Local brick-making began around the 15th century with kilns fired using wood or charcoal. By the 16th and 17th centuries, brick, although still expensive, was being used in timber-framed buildings to replace earlier wattle-and-daub.

From the early 19th century, coal brought by canal or railway was used to fuel the kilns and so cheaper brick became the dominant building material. This was the hey-day of the local brickworks.

Limestone is sourced from outside of the area. The Jurassic oolitic limestones quarried in the Cotswolds of Oxfordshire are the most commonly used in this region.

However, the need to import limestone made it expensive. Traditionally it was only used for prestigious buildings such as churches and wealthy merchant or manor houses.

The use of flint with limestone characterises the majority of church buildings. The limestone is used primarily for dressings such as the basal plinths, cornerstones, window and door frames and buttresses.

Local field flints, embedded in mortar, were used to build the rough walls of Saxon and Norman churches, although the cornerstones and window surrounds had to be made of larger blocks of cut Jurassic limestone brought from outside of the area.

The Oxfordshire Geology Trust was launched in 2000 to protect and conserve geological sites and the landscape, and to raise awareness of the county's rich and varied heritage and geology. The OGT was funded by the North Wessex Downs AONB to complete the Diversity in Stone project. For more information on OGT, write to The Geological Records Centre, The Corn Exchange, Faringdon SN7 7JA , call 01367 243260, email contact@oxfordshiregt.org or visit the www.oxfordshiregt.org website. To find out about the North Wessex Downs AONB, visit www.northwessexdowns.org.uk Looking After an Old House, looking at timber-framing and wattle and daub, is on May 10 at 9.30am-5.15pm, in Blewbury. To book call 01235 850836. Picture courtesy of Oxfordshire Geology Trust