16 CONTEXT 189 : SEPTEMBER 2026 Two roofs: (right) with clay plain tiles to supplement Horsham slabs, and (left) with Horsham slabs ‘stretched’ to single lap (Photo: Matthew Slocombe) A streetscape with Horsham slab roofs, East Grinstead, WestEast Sussex border (Photo: Matthew Slocombe) MATTHEW SLOCOMBE Horsham roofing stone The difficulty in obtaining this regionally important, distinctive roofing material means that hard choices are being forced on owners, advisers and planning authorities. Heritage Crafts maintain a Red List of endangered skills; Historic England and some local planning authorities have lists of historic buildings ‘at risk’. Sadly, though, nothing comparable exists for traditional building materials, yet many are now unavailable or extremely difficult to obtain. Examples include Swithland roofing slates from Leicestershire, Marram grass for coastal thatching and the Horsham stone roofing slabs used in parts of Sussex, Surrey and Hampshire. Natural stone for roofing comes in many forms. ‘True’ slates include the purply-blue examples from Penrhyn in north Wales, the blue-greys from Delabole in Cornwall and the thicker green-grey slates from Westmorland. Additionally, some sandstones and limestones are sufficiently fissile to be usable for roofing. These roofing stones vary in texture, colour and geological type, contributing to local character. The relatively slender stone slates of Collyweston in Northamptonshire differ markedly from the substantial Purbeck slabs from Dorset or the Yorkshire Greys. Among the weightiest of all roofing stones are the Horsham slabs of the south east, requiring a robust roof structure. Horsham roofing stone is a Wealden sandstone of the Cretaceous period, roughly 130 million years old. Lower Horsham beds contain a hard building stone, but the layer above has the potential to laminate under the action of frost. This produces slabs suitable for paving or roofing. Historic England’s Building Stones of England: West Sussex (2023) explains that ‘Horsham Stone slate… is the most important indigenous roofing stone in the county… [found to] the south and west of Horsham.’ This area, around Christ’s Hospital and Southwater, is generally considered the centre of Horsham roofing stone production, with roofs found in a 15–20 mile radius from this location – from the Hampshire-Surrey border, over to the northern meeting point of East and West Sussex, and down to the south coast. This radius may offer evidence of transportation limits in the past, but it is also possible that Horsham roofing stone was extracted locally from other outcrops. The county is peppered with quarrying delves, and Sussex was known historically for its difficult roads. Horsham roofing stone is a high-status material with a long history of use. Examples have been found on Roman sites such as Bignor Villa in West Sussex, and in the medieval village of Hangleton, near modern Brighton, which was deserted by the 1340s. Horsham slabs survive on standing buildings from the medieval
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