Chapter one
Horsham slab roofs on Tarring High Street
Existing stone slates go back on before any new ones are bought, and a repair ought to blend into the roof around it.
The Victoria County History says most of West Tarring's old buildings are of brick, flint and cobbles, some painted, rendered or tile-hung, with roofs of tile, slate or Horsham stone slab. The council's appraisal adds that High Street properties are two-storey with steep pitched roofs, several on medieval timber frames later refaced in flint, brick and render. Behind that refacing, the loft is the best place to begin. Rafters that have moved, battens rotted at the eaves and wall plates, the timbers that carry the rafters' feet, gone damp all show themselves there well before a stain reaches the ceiling below.
At a glance
- Horsham slab is a flaggy, lime-bearing sandstone
- Slab sizes step down from the eaves towards the ridge
- Stone already on the roof gets reused ahead of anything new
1.1 How a stone slate roof is laid
Horsham stone slates, to quote the Stone Roofing Association, are calcareous and flaggy sandstones, and two laying systems exist for them. Double lap is the usual one; single lapping, a method found only on Horsham stone roofs, weathers the joints with slivers of Welsh slate, called shadows, bedded in mortar. Either way the slabs vary in size, with the biggest at the eaves, shrinking steadily to the smallest at the ridge. Wherever it can be done, the Association wants double lap kept or restored. Moving between single and double lap means checking the loading and stability of the roof, so building control approval follows, along with a church faculty where that applies and listed building consent for a listed building.
1.2 Reuse first, then new, then reclaimed
On the Association's advice, a repair should begin by returning as much of the roof's existing stone to the roof as it can. If suitable new Horsham slates are available, they should make up any shortfall. Slates taken from other buildings are best avoided, since a market for them speeds the loss of historic roofs, and if they cannot be avoided the supplier should show they were obtained legitimately. A 2019 report quoted a heritage building charity on a supply crisis affecting Horsham stone roofing slabs, so a stone repair may need a wait while suitable slates are found. The slabs come up and are graded by size, the battens under them are renewed, and the slabs are laid again in order. Afterwards you get a written note of how many of your roof's own slabs went back. A split slab is replaced from the new or reclaimed stock and placed on the least conspicuous slope. Our Horsham stone roofing page covers the method.
Horsham stone roofs at a glance
- The stone
- Calcareous, flaggy sandstone (Stone Roofing Association)
- Laying systems
- Double lap, and single lap unique to Horsham stone
- Course sizes
- Biggest slabs low down, smallest at the top
- Single lap to double lap
- Review loading first; approval routes may apply
- Supply
- A crisis of supply reported in 2019
Source: Stone Roofing Association, Horsham Stone Roofs (2nd edition); Stone Specialist, 31 July 2019, fetched October 2026





