20 CONTEXT 189 : SEPTEMBER 2026 Matthew Slocombe is chief executive of the Society for the Protection of Ancient Buildings (SPAB) and author of the Shire Book of Traditional Building Materials. With thanks to Terry Hughes, Chris Wood, Nicola Westbury, Clarke Roofing and Dale McCabe Further reading Historic England (2023) Building Stones of England:West Sussex Stone Roofing Association (2009) Horsham Stone Roofs Historic England (2015) Strategic Stone Study: a building stone atlas ofWest Sussex Roger Birch (2006) Sussex Stones: the story of Horsham stone and Sussex marble Alternative options have been discussed with the conservation officer in the event of a large quantity of replacement Horsham slab being needed and difficulties in obtaining it being met. These options included transferring slab from the short gable end to the main slope, or if no other options are available transferring sound slab to a smaller slope and using Kent peg tiles on the east facing slope… we shall be making decisions about whether to buy in additional stone… to reuse the salvaged stone (which was laid double lap) as single lap to eke it out, or to keep double lap and introduce peg tiles at the ridge and/or hip.’ As these examples illustrate, a point has been reached where difficult choices are being forced on owners, advisers and planning authorities. The real answer, of course, is to revive supply. There was some resumption of production on one site near Horsham in the early years of the 21st century but this source is no longer regularly available. Historic England has encouraged Horsham Council to support production, and in 2019 a group, including SPAB, the Stone Roofing Association, local authority conservation staff, Historic England and conservation professionals wrote an open letter to the chief executive of Horsham Council urging a new approach. The plea, which came at the time when a county minerals policy was under review, was that the planning system could assist a resumption of supply of Horsham slabs. With much new housing development in the Horsham area, excavation for construction offers possibilities. Horsham stone for roofing is The 15th century farmhouse at Standen shortly after reroofing, clearly showing the stretched-out single lap (Photo: Matthew Slocombe) not deeply buried (a depth of 3–4 metres below the surface is common) and with many sites newly cleared for housing, some are likely to contain stone suitable for roofing. A partnership between developer and quarry could yield stone which is commercially valuable as well as of conservation benefit. Examples elsewhere suggest that Horsham’s case may not be hopeless. Quarrying of Scotland’s distinctive, small, textured ‘true’ slates had ceased some time ago, but a recent initiative on the Isle of Luing has brought a welcome revival of supply. Collyweston roofing stone in Northamptonshire had ceased to be available but an initiative by Claude N Smith Ltd, encouraged by Historic England and others, has revived the supply. The quarrying operation combines traditional quarrying with innovative techniques. In the past, the splitting of stone into thin roofing slates was lengthy and laborious. To speed the process, Claude N Smith now use container-freezers to accelerate natural effects before splitting. Stones are then hand-dressed and sorted into 26 sizes that can be used on roofs with diminishing courses. The draft National Planning Policy Framework, under review following consultation in early 2026, has some useful clauses about mineral policy, covering both stone and brick, but more could be said about materials for conservation work. If historic roofs, that are much-enjoyed and help define the character of an area, are to be sustained, public and private sector support is needed for the production of suitable new materials.
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