The short answer
Stone tiles on the oldest buildings, Welsh slate on many later ones, and tile or modern materials on the newest. A local appraisal says stone tiles were everywhere on the A4 corridor until slate began arriving around 1790, so what is on a given roof often hints at its age.
Reading a Corsham roof is a little like reading a page of local history. The covering suggests when the building went up, or when the roof was last renewed, and that shapes how we approach a repair.
Q1.1Why were stone tiles so common here?
Stone was on the doorstep, heavy goods were costly to move, and the district had skilled quarrymen and masons already on hand to cut and lay it. A conservation area appraisal for Pickwick, next door, says stone tiles were found everywhere along the A4 Bath road from Calne to the centre of Bath until about 1790. Slate arrived with imports and then with the canal, and the same document says very little reached Corsham until the canal came as far as Lacock. Those are regional statements, but they fit what a roofer sees on older buildings here.
Q1.2What happens when slate replaced stone?
A roof structure designed for stone is heavy and strong, so it can carry slate easily; the reverse is not true. Slate is lighter, thinner and laid in even courses. Where a historic stone roof has been swapped for slate, the rafters can be more than strong enough, but the look of the street has changed. Our slate roofing page sets out what we check on those roofs.
Q1.3How can you tell which covering you have?
Stone tiles are thick, uneven and laid so the biggest sit at the eaves. Slate is thin, flat and uniform. Concrete and clay tiles are interlocking or plain, with a regular profile. If you are unsure, a photograph sent by WhatsApp is enough for us to give you a first opinion.
Knowing the covering matters because each one fails in its own way and needs its own repair. A cracked stone tile, a slipped slate and a split concrete tile call for different materials and fixings, and the quote reflects whichever of them your roof actually needs.