Ridge and verge faults tend to show themselves in winter, when a gale brings down a tile or a hard frost opens a crack that has been there all year. The natural reaction is to want it fixed at once, and then to wonder whether anyone can do a proper job on a roof in January. The truth is that some work can go ahead in cold weather and some cannot, and the difference is mostly about mortar. Water in fresh mortar freezes, and frozen mortar is weak mortar. This guide explains what frost does, how lime and cement behave differently, why dry-fix work is less fussy about the weather, and how we decide what to do straight away and what to leave until the forecast improves. Safety up on the roof counts for as much as the choice of material, so that is covered here as well.
What frost does to fresh mortar
Mortar is sand, binder and water. The binder, whether lime or cement, stiffens as the mix reacts and dries. While that is happening the mortar holds a lot of free water in its pores. If the temperature drops to freezing before the mortar has hardened, that water turns to ice and expands.
The expansion pushes the grains of sand apart and breaks the early bonds that were forming. The mortar may look fine when the ice melts, but it has lost strength. Often it crumbles to a sandy powder within a season, and the ridge tiles it was meant to hold are loose again. A bad frost on a newly bedded ridge can undo a whole day's work without leaving any visible mark.
The danger is greatest in the first days after laying, when the mix is wet and weak. It is also greatest on an exposed ridge, where the cold air sweeps over the top of the roof and nothing shelters the work. A still, clear night after a damp day is the classic risk, because the temperature can fall a long way before dawn.
For that reason a roofer will not lay mortar on a day when frost is forecast overnight, and will not trust a mix that has been left out in the cold. Where a patch of work has been caught, the proper remedy is to rake out the damaged mortar and re-lay it, not to leave it and hope.
Lime and cement in the cold
The two main mortar types behave differently when the weather turns. Cement mortar gains strength through a quick chemical reaction, and it is the more forgiving of a damp day. It still needs to be kept above freezing while it hardens, and it dislikes being laid on a frozen or soaking base.
Lime mortar is slower. Hydraulic lime sets partly by reaction with water and partly by slowly absorbing carbon dioxide from the air, a process that can run for weeks. That slow set is what makes it breathable and gentle on old tiles and stone. It also makes it more vulnerable in winter, because it stays soft and wet for a long time. Lime laid in a cold spell and then frozen is likely to fail, and in the worst case it never fully hardens.
Heritage bodies are firm about using the right mortar. In a casework comment on a Walcot Buildings chimney, the Trust wanted lime used for the flaunching (the sloping mortar fillet at the foot of the pot) and noted that cement may have harmed the stack. The same principle applies to a ridge: the right material, laid when the weather suits it. Our page on lime mortar ridges goes through the mix itself.
In practice, this means that lime work is generally held for a milder period unless the repair is urgent and can be protected. Cement work can sometimes go ahead on a cold but frost-free day. Neither is attempted on a frozen roof, in rain that would wash out the mix, or when the temperature is about to fall.
Why dry-fix is easier in winter
A dry ridge or dry verge system uses no wet mortar. The ridge tiles are held by a rail, clips and screws, and the weather seal is a roll or strip laid along the top. There is no mix to freeze and no waiting for anything to cure, so the main limits are wind, rain and ice on the roof. That makes dry-fix a sensible choice when a ridge has to be done in the cold months.
The standards back the method. Under BS 5534:2014 a ridge, hip or verge piece needs a mechanical fixing, while dry-fix systems are tested under BS 8612:2018. A dry ridge also has the advantage of being finished the moment the last screw goes in. The roof can be left finished when the light goes, with nothing wet exposed to an overnight frost.
It is not always the right choice. A listed building, or a roof whose appearance matters, may call for a bedded ridge in a matching mortar, and the council may expect that. Some tile shapes do not suit a standard dry system. Where that is so, the decision becomes one of timing: do the temporary make-safe now, and the permanent bedded repair in spring.
Typical UK cost is the same in any month. One third-party guide (MyBuilder, 2026) puts the system at £40 to £60 a metre run. The actual price for your roof depends on the ridge length, the number of hips and the scaffold, and you receive it in writing after the survey.
What we can do straight away in cold weather
Not every ridge or verge job needs mortar, and some jobs are mostly about stopping water getting in. When a tile has come off in a storm, the priority is a roof that is secure and keeps the rain out. That can mean refixing a loose tile with a mechanical fixing, covering a gap with a temporary measure, or stripping a dangerous piece before it falls.
Leaks and storm damage are our priority. Where rain is coming through, the first visit is about stopping that, and the lasting repair waits for suitable weather. Why ridges and verges give way first is covered in wind and storm damage to ridges and verges.
A single lost ridge tile can often be replaced on a cold but dry day, provided the new tile is held by a fixing and not left to sit in wet mortar alone. That job is described on the page about replacing a single ridge tile. A longer run of loose bedding is a different matter. Rebedding a length of ridge in mortar is better left for a spell of settled weather, with the loose tiles secured in the meantime.
We judge each case on the roof. The factors are the forecast, the mortar to be used, whether the work can be protected with covers, how wet the existing masonry is, and whether anyone can reach the roof safely. If the permanent repair cannot be done properly yet, we tell you that, and the temporary measure and the later visit go in writing.
Ice, wind and working at height
Mortar is only half the question. A frosty roof is slippery, ladders are unsafe on iced ground and a light dusting of snow hides loose tiles. Short days also matter. The light fades early in midwinter, and a job started late can be left half done as it gets dark. None of that is a good reason to skimp on a repair, but it is a good reason to plan the visit.
Wind speed matters even more on a ridge, because the ridge takes the full force of any gust. Lifting a ridge tile or a long length of verge into a strong gust is risky for the roofer and for people below. We will not work at height when conditions make it unsafe, and we would rather re-book than rush.
Scaffold is a sensible response where the work is extensive. A properly boarded scaffold gives a stable platform and an edge that protects people on the ground. It is a cost, but on a long ridge or a tall house it can be the difference between a careful repair and a hurried one. For a ladder-height job, access may be adequate, and we will tell you which applies.
If you need to inspect from the ground, wait for daylight and dry ground, and look from a safe distance. Do not go onto a roof yourself to check a tile. A photograph from a distance is more use than a risky climb. Our page on ridge repair costs explains how access affects the price.
Planning ridge and verge work around the weather
If the work is not urgent, there is real value in planning it for the best part of the year. Spring and early summer give long days, dry spells and warmer nights, which suit lime and cement alike. A booked job in a settled week is more likely to be done calmly, to a good standard, and without a tarpaulin standing by.
If you have noticed signs of trouble, a survey in autumn gives you time to plan. Look for gaps or loose mortar along the ridge line, tiles that have shifted, and mortar debris in the gutter. If we find them, you can decide whether to do a temporary measure for the winter and a full rebedding in the spring, or to book a dry-fix upgrade in the cold season.
It also helps to think about what a delayed repair costs. A small gap at the ridge can let water into the loft. Wet insulation, rotting battens and staining on the ceiling can follow, and they cost far more than the ridge repair. So the right answer is rarely to wait without doing anything. It is to make the roof safe now and to pick the right moment for the permanent fix.
In Bath, with so many older houses and some listed roofs, matching the mortar to the building matters more than speed. A lime mortar that is matched in colour and texture, laid in good conditions, will outlast a hurried mix in the wrong weather. The wider service sits under ridge and verge repairs, and the survey will settle the plan for your roof.