Horsham Stone

Horsham stone is a calcareous, flaggy sandstone from the Weald of south-east England, around the town of Horsham in West Sussex. Split into large, heavy slabs, it was used as roofing on churches, manor houses, mills, barns and dovecotes across Sussex and neighbouring counties, and its thickest slabs were used for paving.

Geology

The stone formed about 130 million years ago in the Lower Cretaceous, when sands rich in quartz and mica were deposited in the Wealden Basin. Ripple marks preserved on many slabs record the action of water on the ancient sea or lake bed. It occurs in bands about 10-13 cm (4-5 in) thick just below the surface of the Weald Clay, in an arc several kilometres around Horsham.

Use on roofs

Like other English stone slates, Horsham slabs are laid in diminishing courses, with the largest at the eaves. Historic England classifies it among the sandstone stone slates of England, which should not be mixed with limestone slates on the same roof.

History

• The earliest recorded use is from the Bronze Age, in quern fragments found at Amberley Mount.
• The Romans used it for the Stane Street road and for floors and roof slates at the villas of Bignor and Fishbourne.
• Large-scale commercial extraction had stopped by the 1880s, and regular quarrying ended in the 1930s.

Supply

With the old quarries closed, Purbeck stone was often used as a cheaper substitute in repairs, though it is a limestone. The Nowhurst quarry, reopened in 2004, produces roofing slates for historic buildings. Heritage guidance recommends like-for-like replacement where possible.