Woodchester Mansion is built in Cotswold stone, and the stone-slate tradition belongs to the same limestone country. Stone slates are laid with the weightiest pieces forming the lowest rows and the thinnest near the top, so the roof tapers as it climbs. Roofers call that pattern diminishing courses.
Q2.1What do stone roofs need to last?
Attention before they fail. The Cotswold District Council guidance of 2000 says regular yearly scraping of a stone roof could double its life, and that about half the slates were frequently found decayed when a roof was finally stripped. Pegs, usually oak, rot and let stones slip. Moss holds water against the stone, and a blocked gutter feeds it. A yearly look from the ground with binoculars costs nothing and finds the first slipped stone.
Q2.2Can stone be swapped for a modern lookalike?
Policy from English Heritage, set out in that Cotswold District booklet, treats concrete and reconstituted copies as unsuited to historic buildings, and on a listed house the loss of natural roofing can be refused outright. Even where nothing is listed, a lookalike weighs less, sits differently and ages differently. Our Cotswold stone roofing page covers the choices.
Q2.3What does repair look like in practice?
The roof is photographed and the stones are sorted by size as they come off. Rotten pegs and battens are replaced, the same stones go back in the same order, and broken ones are made up with matching stone. Swept valleys, where specially cut slates curve through the angle, are rebuilt in the same way instead of being replaced with a plain lead trough.
It takes longer than patching, but the roof then carries on for decades, and it still looks like the roof your house was built with. That is worth having on a lane where the stone is what people notice.