Walling Stone

Purbeck Limestone dry stone wall on the South West Coast Path

Dorset is world-famous for the dry stone walls of Purbeck Limestone on the Isle of Purbeck and along the South Dorset Ridgeway. However, the rich geodiversity of the county provides a wide range of local walling stones. These are listed below, from the geologically oldest, to the youngest.

Blue Lias

Blue Lias strata in cliffs near Lyme Regis

The Blue Lias Formation consists of alternating layers of limestone and mudstone. Blue Lias limestone was historically quarried in south-west Dorset from the cliff faces and foreshore at Lyme Regis and Charmouth. Also, from inland quarries in south-east Devon at Uplyme. Currently, it is available from quarries in south Somerset around Glastonbury and the Polden Hills.

Mortared Blue Lias wall in Lyme Regis

The blue-grey colour is due to fine particles of pyrite (iron sulphide) within the stone. Some beds of Blue Lias, with high clay and pyrite content, are prone to weathering, in part due to oxidation of the pyrite to ochre minerals. This problem is exacerbated by the use of impermeable cement-based mortars which result in increased water-penetration and frost-damage to the stone surface.

Blue Lias dry stone wall

Dry stone construction without mortar, or the traditional use of permeable lime-based mortars, allows Blue Lias stonework to naturally dry-out, and makes it less prone to weathering.

Thorncombe Sand

Doggers in the Thorncombe Sand in a sunken lane near Symondsbury

The Thorncombe Sand exposed in the cliffs near Eype Mouth shows three lines of ‘doggers’, rounded boulders of sandstone naturally cemented with calcium carbonate (calcrete). These doggers are also visible in sunken lanes around Symondsbury, where they were quarried and used locally in buildings and walls.

Beacon Limestone

Beacon Limestone exposed in a sunken lane near Symondsbury

The Beacon Limestone Formation is exposed on the cliff-face of Thorncombe Beacon, near Eype Mouth. It is also known as the Junction Bed as it occurs at the junction between the Middle and Upper Lias. It is visible in sunken lanes around Symondsbury and was used in some  rubble walling. It was also quarried and used in north Dorset, around Nether Compton, Trent and Sandford Orcas. In south Somerset, many old buildings in Yeovil are constructed of Beacon Limestone, locally known as Yeovil Stone.

Bridport Sand

Resilient limestone cemented bands in the Bridport Sands of East Cliff, West Bay

The Bridport Sand Formation contains distinctive resilient calcium carbonate-cemented bands exposed in the cliffs to the east of West Bay and sunken lanes to the north of the county. The freshly exposed stone has a bluish colour due to the presence of iron minerals, though the surface oxidises to give the characteristic ochre colour.

Mortared wall of limestone-cemented Bridport Sand at West Bay

Blocks of this calcium carbonate-cemented sandstone are used for harbour buildings and walls at West Bay and the stone is locally used in rubble walls, elsewhere in the County.

Ham Hill Limestone

Dry stone wall of Ham Hill Limestone on Ham Hill

The Ham Hill Limestone Member is a very localised limestone deposit within the Bridport Sand Formation, only found on the Ham Hill plateau near Montacute in Somerset.

Ham Hill Limestone window in wall of Corallian limestone and Portland Stone. Church of St. Nicholas, Abbotsbury

Ham Hill Limestone is a fine grained freestone that takes detailed carving. It is used as an architectural stone throughout the region. Many Dorset churches are largely built from local stone but have carved doorways and windows of Ham Hill Limestone.

Inferior Oolite

Inferior Oolite reef at Black Rock, West Bay

The Inferior Oolite is exposed on the foreshore at West Bay and at the top of the cliff at Burton Bradstock.

Dry stone wall of Inferior Oolite (Burton Limestone) near Burton Bradstock

Inland, it was quarried as Burton Limestone along its outcrop from Burton Bradstock, through Bridport, Loders, Mapperton and Beaminster to Broadwindsor.

Dry stone wall of Inferior Oolite (Hadspen Stone)

To the north around Nether Compton, Sherborne and Oborne the inferior Oolite forms a thick deposit of building stone, Sherborne Limestone. Further into Somerset, Inferior Oolite is still quarried as Hadspen Stone, near Castle Carey, and Doulting Stone, near Shepton Mallet.

Fuller’s Earth Rock

Mortared cottage wall of Fuller’s Earth Rock, Thornford

In north Dorset, the clay of the Fuller’s Earth Formation contains a limestone member, the Fuller’s Earth Rock. This forms a scarp to the south and west of Yeovil and is used locally as a building stone and in rubble walls.

Forest Marble

Dry stone wall of Forest Marble sandstone, Langton Herring

Cornbrash

Upper Cornbrash exposure, Butterstreet Cove, East Fleet

Corallian

Dry stone wall of Corallian Abbotsbury Stone with Upper Greensand chert cope stones

Kimmeridge Clay

The Old Pier Kimmeridge Bay. Constructed around 1860 from the Yellow Ledge Stone Band of the Kimmeridge Clay Formation, originally consolidated with hydraulic cement

Portland Sand

Road cutting through the Corton Hill Member (Scar Cementstone or Exogyra Beds) of the Portland Sand Formation, at the entrance of Corton Farm

Portland Stone

Dry stone reconstruction, using blocks of Portland Freestone. of a retaining wall at the High Angle Battery, Portland

Purbeck Limestone

Dry stone wall with inclined courses of thinly bedded Middle Purbeck Limestone (Stair Hole Member)

Upper Greensand

Upper Greensand Cowstones in the Cobb at Lime Regis

The lower part of the Upper Greensand Formation comprises the relatively unconsolidated sands of the Foxmould Member. However, the Foxmould does contain some large rounded calcrete doggers, locally known as Cowstones. These have had some use as building stones and make up the core of the Cobb harbour wall at Lyme Regis

Upper Greensand (Eggardon Grit) foundation and cope stones in a dry stone wall of Abbotsbury Oolite

Chalk

Mortared estate wall of Chalk (clunch), Upper Greensand and Corallian Limestone, Shroton (Iwerne Courtney)

Flint

Dry stone wall using unknapped field flint

Heathstone (ferricrete)

Fallen Ironstone doggers below the cliffs of Hengistbury Head

Sarsens (silcrete)

Sarsen stone circle, the Nine Stones, near Winterborne Abbas. Probably built in the late Neolithic to Middle Bronze Age (about 2500-1000 BC)