How many old stone slates can be reused?

The figure comes from the technical note on Cotswold stone slate roofing that Cotswold District Council published in April 2000. Its remark is that around 50% of the slates have usually perished when the roof is taken apart. The note is old, and the remark is general rather than a measurement of any single roof, so treat it as a planning allowance and not a forecast.

Perished means the stone has lost its face, split along its beds or crumbled, so it no longer sheds water or holds a peg hole. Frost is the usual culprit, since water held in the stone expands as it freezes. Moss keeps a slate wet and makes matters worse, and the council suggests that yearly scraping can double a roof's span.

Two roofs of the same age can therefore give back very different amounts. A well-kept slope may return most of its stone, and a neglected one far less. We cannot tell from the ground, and we do not guess.

Stripping stone is slow because every slate is handled. As each comes off it is checked, tapped for soundness and stacked by length. The sorting follows the roof's structure. Every large slate comes with many small ones, so courses diminish from the double eaves course, where slates run to roughly 600 mm and sometimes 750 mm, to the top, where the smallest are only 150 mm. Mixed sizes cannot be laid back in graded courses.

Slates are rejected for deep cracks, delaminated faces, broken heads where the peg hole sits, and thin or crumbling edges. Those that pass go back, each course drawing on its own size group.

Cleft oak pegs usually go in new, because pegs are the part most likely to have rotted. That is why our answer on re-laying a Cotswold stone roof treats refixing as part of the job and not an afterthought.

When half the stone cannot go back, the roof needs topping up. English Heritage policy, as printed in the council note, leans toward fresh-cut stone slates rather than salvage wherever it can. New slates should echo the existing roof in rock, colour and dimensions, and salvaged ones belong only where they were taken from. So the shortfall is filled with new matched stone, not stone bought from another demolished roof.

That also keeps you clear of a dubious market. The council note links second-hand demand to the stripping of other old buildings, occasionally through theft, so buying reclaimed stone of unknown origin is not a neutral choice.

The note also says limestone slate imported from France has served well on a few local projects, and a matched limestone is how we would approach topping up. Sandstone is no alternative; our answer on dormers on Cotswold stone roofs assumes limestone throughout.

Reuse rate is the largest unknown in a stone re-lay, because new stone costs more than the stone you already own. Checkatrade's 2026 slate guide lands on £160 to £210 per m² for stone overall, and the exact number turns on the stone's source and your locality. It is not Cotswold-specific and does not tell you what your own roof will cost.

What we can do is publish typical prices first and give a written quote after the survey. Following the survey, the written quote covers scaffold, strip, sorting, new stone, pegs, battens, labour, waste and repairs. The new stone allowance rests on a stated assumption for the shortfall, and any change once the roof is stripped is judged against that, so you can see what the actual reuse rate did.

Steep lanes and terraced hillsides affect the scaffold, and we plan for that. Your quote shows VAT, which roofing normally attracts at the standard rate.

Stored stone needs a proper home. Keep sorted slates dry, off the ground and out of sight of the road, and write down what you hold by size. Our answer on buying a stone-roofed house explains why a record of earlier re-laying helps a future buyer.

Listed or in a conservation area? Ask Stroud District Council's planning team before anything is stripped. The district has 41 conservation areas, and the council says protection extends to the whole of a listed building. Consent is explained to you, and notifiable work is reported to building control by us.

A survey from us includes photographs of your roof that show slipped, flaking and mossy areas, which helps us judge the likely reuse. Our workmanship is guaranteed in writing for 10 years. To talk it through, ring 01453 933613, or write via WhatsApp or the enquiry form. More about the service is on the Cotswold stone roofing page.

Once a section is down, patterns show up. Slates near a failed valley or a blocked gutter are often soft, because water sat on them for years. Slates under a chimney or beside a dormer may be sound. Courses near the ridge, the smallest and thinnest, can perish first because they have less body to resist frost.

We share what we see as the work goes on, with pictures, so that a rise in the new-stone line is never a surprise. That is the practical benefit of pricing the allowance openly before the first slate is lifted.