A 2000 note from Cotswold District Council on stone slate roofing makes a claim every owner of an old roof should hear: kept up properly, a Cotswold roof can last a century with ease, and possibly 200 or 300 years. It also points out that many roofs being replaced on the oldest buildings are thought to be original. Stone is a durable material, and the failures we are called to mostly come from neglect of the details around it rather than the stone itself.
This guide covers all of the upkeep, in the order a roofer would walk it: what is visible from the pavement, what needs a ladder or a survey, how to deal with moss, pointing and gutters, and how a few small jobs add up to a long life. It is the overview for the whole subject. The service summary is on our Cotswold stone roofing page, and the single question of scraping moss has its own answer, should moss be scraped off a stone roof.
Why upkeep decides how long a stone roof lasts
The council's guidance says that historically Cotswold roofs were well maintained and kept free of moss that holds moisture. Scraping was a common job, but it has been mostly discontinued, partly because of the expense. The guidance calls that a false economy. Many roofs now needing near-total replacement would have needed only a few new slates if they had been scraped. It adds that a yearly scrape might give the roof twice the working life.
It is a striking claim from a guidance note, so we treat it as an informed rule of thumb rather than a measured result. The mechanism is easy to see. Frost is the principal agent of decay in stone roofs. A slate that stays wet under a mat of moss takes in water, the water freezes, and the stone splits along its bedding planes. Keeping the surface clear stops the cycle starting.
Two kinds of failure
Roofs fail in two ways. In the first, the stone itself delaminates and perishes. The same note says a stripped old roof often turns out to have lost about half its slates to decay. In the second, the fixings and the details fail while the stone is sound: pegs rot, flashings lift, pointing falls out, a gutter blocks and overflows onto the wall. The second kind is cheaper to fix and more common than people expect, and it is what an annual check is for.
Big jobs avoided
A single slate that has slipped will let in water for years if nobody sees it, and the damp may rot the batten, the rafter and the ceiling below before it shows. A re-lay of a slope costs a great deal more than the slate would have. This is why we say that the best time to look at a stone roof is before there is a problem.
The annual look: from the ground, then from the roof
Pick a dry day and take a pair of binoculars. You can learn a great deal without leaving the ground, and the whole check takes less than an hour on an ordinary house.
From the ground
Look along each slope for gaps, for slates that sit proud of their neighbours, and for courses whose tail lines dip or wander. Check the ridge for a line that has opened up. Take in the chimney stack, the valleys, the verges and every spot where a slope butts up to a wall. Scan the wall below the eaves for green staining, which can mean an overflowing gutter. Inside, look at the ceilings and the loft for new stains, and for daylight through the roof, which should not be there.
Debris in the gutters
Fallen leaves and bits of stone shed from the slates collect in gutters and valleys. A blocked gutter overflows over the wall, and in cold weather the water can freeze at the eaves.
From the roof
A full inspection means walking the slopes or using ladders and a roof ladder, and it should be done by someone who is used to stone, because a stone roof is heavy but can be easily broken underfoot. We lift loose slates to look at the pegs and battens. The photographs we take go into the report.
MyBuilder's 2026 roof inspection cost guide gives £150 to £500 for a roof survey, with a standard inspection at £150 to £250, a drone survey at £200 to £400 and a thermal survey at £300 to £500. A drone is useful on a tall or steep roof where access is awkward, which is common in the valley lanes around Stroud. Our quote after any survey is in writing, and the report lists what needs work, in order of urgency.
Slipped slates, pegs and battens
Each stone slate is held by a single oak pin, cleft from the log and pushed through a hole near its upper edge, so the slate hangs over the batten. Nothing else holds it. When a slate slips, one of a small number of things has happened.
Why slates slip
The peg may have rotted or snapped, so the slate is no longer hanging from anything. The hole may have broken through the slate at the head, which can happen when stone has delaminated. The batten may have decayed, so the peg no longer has anything to hang from. Or the whole slope may have moved, because the timbers under it have sagged. Before fixing we rule out all four, since renewing the slate without finding the cause only invites a repeat.
A slight bow is normal
The council's guidance says that the heavy weight of a stone slate roof often causes a slight bend in the roof, and that it is now thought that roofs were made deliberately to allow this bow, because it packs the slates more closely together and keeps out rain and snow. So not every dip is a fault. We look at whether the slope has moved lately. A new crack in the ceiling or a new gap in a verge is more telling than a bow that has been there for a century. Our note on the structure behind a stone roof goes into the timbers.
Replacing a slate
A good repair uses a stone of the same type, colour, size and thickness, and hangs it on a new peg. Where the old slate is intact, it can sometimes be re-hung. Single slates in a slate roof cost £60 to £120 each, according to MyBuilder, but that is for natural Welsh or Spanish slate and not stone, so it is not a stone price. We price stone work on survey, with the stone named in the quote.
Pointing, ridges and mortar
Mortar plays a smaller part on a traditional stone roof than on a tiled one, but it still matters in a few places: the ridge, the hips, the verges, the chimney stack and the abutments, where a slope runs into masonry.
The ridge
On a traditional Cotswold roof the ridge is cut from dressed stone in a plain angle, with a roll-topped version reserved mostly for churches and other grander buildings. Ridge stones are bedded on mortar. Over time the bedding weathers and cracks, and a ridge stone that moves is a danger to anyone below it. BS 5534 was revised in 2014 and stopped treating mortar as enough alone to secure ridge and hip pieces, so mechanical fixings go in alongside it. MyBuilder's range for re-bedding or renewing ridge tiles is £300 to £600, and £200 to £400 to repoint a ridge or hip; those are national figures for tiled roofs, so we price a stone ridge on survey.
Which mortar
On an old stone building, lime mortar is the traditional choice, and it is usually the right one. It is softer and more flexible than cement, so it gives before the stone does. Our guide to lime mortar on stone roofs explains how it is mixed and applied and why a hard cement repair can do damage.
Chimney stacks
With all four faces in the weather, a chimney stack asks a lot of its pointing. MyBuilder's chimney repair guide puts repointing at about £750 on average, within a range of £500 to £2,000, and flashing repairs at £250 to £1,200. We check the flaunching (the mortar crown around the pots), the flashings and the pointing together on the yearly survey.
Moss, lichen and cleaning without harm
Lichen belongs to the look of an old stone roof, and we leave it be. Moss is different. It holds water against the slate and lifts at the edges, and it is the growth the council's guidance says should be kept off.
Scraping by hand
The traditional method is to scrape the moss off with a hand tool. It is slow, which is why it is expensive, but it is the gentlest on the stone. For cleaning, MyBuilder (2026) lists hand scraping at £5 to £10 per m², pressure washing at £10 to £15 and soft washing at £15 to £20, with a caution that pressure jets can harm delicate tiles. We clean stone by hand scraping, since a pressure jet can drive water into the bedding planes and strip the surface off a soft slate. Our separate answer on scraping moss off a stone roof covers when and how.
Costs for a whole roof
MyBuilder's guide says roof cleaning starts from about £300, with pitched roofs at £450 to £850. Those are general roof cleaning figures and stone is not singled out, so your quote follows the survey.
Biocides and sealers
Chemical treatments are sometimes offered. Ask what is in them and whether the council or a conservation officer would accept them on a listed roof before you agree. Sealants and paints on stone are another thing to avoid, because they trap moisture. Our companion guide to stone roofs in winter explains why timing matters.
Gutters, flashings and the places water gets in
Before gutters came into use, the eaves of a stone roof were projected as far as possible to throw water clear of the wall. Many old stone buildings now have gutters, and they need to be kept clear and in working order, for water sheeting down a wall can damage it as surely as a leak through the roof.
Gutter basics
Gutter manufacturers usually specify a gentle gradient towards the outlet, between 1:600 and 1:350 depending on the product, and brackets close enough together to take the load. A sagging run holds water and overflows. Cast iron gutters are common on older buildings and can be repaired and repainted. Our own check on the survey covers the brackets, the joints, the outlets and the downpipes.
Lead flashings
A flashing is a strip of lead worked between slope and masonry, at a wall or around a chimney. Once it lifts or splits, water gets in at the very point where stone meets stone. MyJobQuote reports lead flashing lasting over 80 years when fitted correctly, longer in higher codes. Lead flashing repairs run at £50 to £70 per metre, and stepped flashing at £80 to £120 per metre for code 5 lead, ex VAT, according to Checkatrade. Our answer on stone roof abutments shows the detail.
When to call us
Call us for a stain on a ceiling, a slate on the ground, a ridge stone that has moved, or a flashing you can see lifting. Leaks and storm damage take priority with us, and we make a roof safe before anything else. Following a survey you get pictures of your roof and a written quote. Our ten-year workmanship guarantee goes on paper when the job is complete, and the waste leaves with us.