Guide
Reclaimed or new Cotswold stone slates: how to choose
Short answer
Reuse your own sound slates first. For the shortfall, heritage guidance prefers new stone slates that match the original stone. Reclaimed slates can come from other roofs, sometimes stolen ones. Whichever you choose, match the stone type, colour, size and thickness, and ask for proof of where the slates came from.
Start with your own slates
The first source of slates is your own roof. When a roofer re-lays a slope, they strip it with care and sort every slate.
Sound slates go back on. Damaged slates can often be dressed down to a smaller size and used higher up the roof. Cotswold District Council guidance says that about half the slates on an old roof have often perished. So most jobs need some extra slates.
What heritage guidance says
Heritage guidance prefers new, matching stone for the shortfall. Cotswold District Council guidance from 2000 quotes English Heritage policy on this.
- Use new stone slates rather than second-hand ones wherever possible.
- Use reclaimed slates only on the building or group of buildings they came from.
- Do not use substitutes such as concrete, fibre resin or reconstituted stone on historic buildings.
- Match the new slates to the old in stone type, colour, texture, size and thickness.
- Never mix sandstone and limestone slates.
- Sawn slates can be unsuitable for historic buildings.
Why reclaimed slates are a problem
Reclaimed slates come off other old buildings. The council guidance says the demand for them has led to the stripping of many old roofs, sometimes through theft.
Reclaimed slates can also be near the end of their life. They may have hidden cracks or frost damage. They may come from a different stone, which can weather differently from yours.
If you do use reclaimed slates, ask for a receipt that names the source. A roofer who cannot tell you where slates came from is a warning sign.
How to match new slates
Match the stone first, then the look. The Stone Roofing Association says to find the original quarry if you can, or else a stone of the same geology.
It also says that stones from the same rock can differ in colour, texture and sizes, and can weather and grow moss differently. Where looks matter, it suggests that you view a roof laid with the new stone at least five years ago.
Ask the roofer for samples. Lay them next to your own slates in daylight. On a listed building, show the samples to the conservation officer before you order.
Practical steps
Follow these steps before you agree a specification.
- Ask the roofer how many of your slates they expect to reuse, and how they will test them.
- Ask which stone they suggest for the shortfall, and why.
- Ask for samples and for the name of the quarry or supplier.
- Ask for a receipt that names the source of any reclaimed slates.
- Ask where they will put the new slates. Some roofers put new slates on a rear slope and keep the old ones on the front.
When to call a roofer
Call a stone slate specialist when a slope has many slipped or decayed slates, or before any re-lay. They can tell you how many slates you are likely to need.
On a listed building, involve the council early. Its advice on the stone can decide the choice for you.
What it may cost
New stone slates and good reclaimed slates both cost far more than most roofing materials. Supply is limited, and laying them is skilled work.
Our guide Cotswold stone roof cost explains what changes the price of a re-lay and of new slates.
Questions
Are new Cotswold stone slates still made?
Yes, but supply is limited. The Stone Roofing Association says frost-split slates of the Stonesfield type are hardly made today.
Can I use imported stone slates?
Some imported limestone slates have been used on Cotswold roofs. Check the match carefully, and ask the conservation officer if the building is listed.
Will new slates look different at first?
Often, yes. New stone is usually paler. It weathers over the years, but each stone weathers in its own way.