The stone slates on a Cotswold roof are limestone, and limestone takes up water. A slate that is soaked in November and caught by a hard freeze can lose a flake from its face or open along a bed. Cotswold District Council's 2000 technical guidance records that one of the two traditional stones, Stonesfield Slate, was frost-split: it was laid out over winter so that the cold would open its layers into slates. The quarrymen used frost on purpose. A finished roof gets the same treatment without anyone planning it.
This guide covers the winter side of owning a stone roof: how frost acts on the slates, what to check after a cold snap, why lime work needs shelter and sometimes a delay, and how we keep a roof dry when it is stripped in poor weather. Upkeep such as scraping has its own answer on scraping moss off a stone roof. The hub page on Cotswold stone roofing sets out the full service.
How frost works on stone slates
Water gets into stone through its pores and along its bedding planes, the layers the rock was laid down in. When it freezes, it expands. In a wet slate that expansion pushes the layers apart, and a thaw lets the water run back in deeper. Repeat that through a cold winter and the face of the slate starts to lift in flakes or sheets. The technical word is delamination.
Why some slates suffer more
Not every slate fails in the same way. A thin or poorly split slate holds less stone to resist the pressure. A slate that is already cracked, or one with a damaged peg hole, takes in water faster. Slates that have been wetted again and again, for example under a blocked gutter or beside a cracked lead flashing, are the ones we expect to flake first.
Sandstone and limestone behave differently
The policy the Cotswold council printed in its guide, from English Heritage, rules out swapping sandstone slates for limestone ones, or the reverse. Frost is part of the reason: the two stones hold and shed water differently, so a mismatched slate in a limestone roof can age and fail at a different rate from its neighbours. Our answer on sandstone and limestone slates goes into that.
None of this means a stone roof is fragile. The same guide says a regularly maintained Cotswold roof can easily reach 100 years and might reach 200 or 300. Frost is one of the forces that decide which end of that range a particular roof reaches.
What frost damage looks like from the ground and the loft
The signs are often small at first, and they show up in the weeks after a freeze, not during it.
From the lane
Look for fragments of stone on a path, a window sill, a porch roof or in a gutter. Flakes the size of a thumbnail or a fingernail point to slates losing their faces. On the roof itself, a slate with a pale, scaly surface where its neighbours are weathered and dark is a candidate for replacement. Gaps in the courses where a slate has slid or fallen are easier to spot after a thaw, when the pegs that held them have loosened.
From inside
In the loft, daylight through a join or a freshly stained rafter points to a fault in the layer above. After a freeze we look for damp patches on the timber and for stone dust or lime crumbs on the loft floor, which come from torching shaken loose by freezing and thawing.
Pegs and fixings
Traditionally each slate is hung from a cleft oak peg (occasionally two) pushed through a hole close to its top edge. Wet wood swells, and a peg that has weathered thin can let a slate drop. Cold and damp together are hard on both parts of the fixing: the stone around the hole and the peg itself.
It helps to photograph the roof from the same spot each autumn. A comparison picture shows slipped slates and bare patches far more clearly than memory does.
Dealing with a freeze-damaged slate
One flaking slate is not an emergency, but it will not recover by itself. What we do depends on how far the damage has gone.
Sound but weathered
A slate with surface loss only, still firm and well lapped, can often stay. The question is whether enough thickness remains to keep water out through another winter. We tap and look at the edges, because a slate that rings clearly is generally in better shape than one that sounds dull.
Failing
A slate that has split along a bed, lost a corner or cracked through the peg hole is replaced. New stone must be of the same rock type as the old, shade, texture and dimensions, and be graded to the course it enters, as our guide to diminishing courses explains. A sawn or uniform substitute does not suit.
Why one slate can turn into many
A slate that fails and is not replaced leaves a gap, and the exposed courses beside it get wetter. In a freeze they flake sooner. That chain reaction is why fixing one slate after the first cold snap is usually a smaller job than fixing a patch after another winter.
MyBuilder's 2026 slate roof guide gives a national figure of £60 to £120 for a single slate repair and £150 to £350 for five to ten slates. Those prices are for ordinary slate rather than hand-selected stone, so the same job on a Cotswold roof can differ. The quote we write after surveying covers scaffold and stone.
A freeze does the most harm to slates that were already wet. Clearing gutters and downpipes in autumn keeps water off the stone before the cold arrives.
Lime in the cold
Lime mortar is the other part of a stone roof that winter targets. Torching, ridge bedding and verge pointing are all made with lime, and lime is particular about its conditions while it cures. Our guide to lime mortar on stone roofs covers the mortar; this section covers the weather.
Why frost spoils fresh lime
Freshly applied lime is full of water. If it freezes before it has firmed, the ice crystals break up the mortar, and what looks fine on the day turns powdery within weeks. Lime putty is the most sensitive, because it hardens by absorbing carbon dioxide, a slow process. Hydraulic lime sets faster and is more tolerant, but it can still be ruined by a hard freeze in its first days.
Why we may wait
Work that does not have to be done now can be left until conditions improve. If torching is crumbling but the slates are sound, a delay of a few weeks costs little. Where a repair cannot wait, we plan it for the middle of a mild spell and protect it with hessian or sheeting as it firms.
Keeping fresh work covered
Fresh lime also needs shelter from heavy rain, which washes out the binder before it sets, and from wind that dries it too fast. In winter that means shorter working sections, a cover ready before the first section is finished, and a check on the forecast before we start and again before we leave.
If pointing is better left until the weather improves, we will tell you so instead of pushing it into a freeze. Mortar that fails in March has to be done twice.
Temporary cover and making a roof safe
When a stone roof is leaking, or has been damaged in a storm, the first aim is to stop water getting in. Leaks and storm damage come first on our list, and the roof is made watertight before any longer repair is discussed.
What temporary cover means
On a damaged slope that might be sheeting battened down over the failed area, a few replacement slates fixed in the worst gap, or a temporary cap over a broken ridge. It is a stopgap for the weather, not a repair. Sheeting has to be fixed so that wind cannot get under it, and it must not be pinned through sound slates, since each new hole is another break in the stone.
Working on a stripped roof
A planned re-lay in winter needs more preparation than the same job in summer. A section of roof is stripped only as far as can be re-covered in the working day, or the whole roof goes under a scaffold-supported cover so that rain does not reach the battens and the loft. Timbers that sit open to the weather soak up water, and wet frame timber is slower to dry out once the slates are back. Our guide to re-laying a Cotswold stone roof describes the process in full.
Protecting the stone
Stripped slates are stacked off the ground on boards, sorted by length and kept covered. Stone left lying wet on a frosty night can take damage before it ever returns to the roof.
The weight of the stone also matters during a winter job. A stack of slates on a scaffold lift or in the loft needs the support to carry it; the timbers are covered in our guide to roof timbers under stone.
Planning stone roof work around the season
Because stone roofing is slow, careful work, a few decisions made early help the whole job.
Book repairs before the cold
The most useful time to deal with loose slates, failed torching and broken pegs is early autumn. Gutters can be cleared, flashings checked and weak slates replaced before the first hard frosts. Work done then is also easier on the lime, which has time to cure in milder weather.
After a storm or a freeze
When the weather turns, walk round the house in daylight and scan the slopes from the garden or the lane. Look at the courses, the ridge line and the gutters, and check the loft for damp. If anything has moved, send us photographs. One clear photograph is a good start, and a survey can follow.
Costs and the quote
On cost, Checkatrade's slate roof guide (September 2026) gives about £160 to £210 per m² for stone slate, depending on whether the stone is new or reclaimed and on location. This is a national guide, not a Cotswold price. Winter working adds items such as temporary cover and extra visits, and these are covered in our written quote, not as a loose allowance. The guide to Cotswold stone roof costs explains how a quote is built.
Consent
Like-for-like repairs do not normally need planning permission, though a listed home or a conservation area with an Article 4 direction changes that, so ask the council. Our workmanship guarantee lasts 10 years and comes in writing.