Can commercial roofs be replaced in winter?

Cold does not stop a roofer; moisture, wind and short days do. The material problems come from three sources. Damp: a covering laid on a wet or frosted deck traps moisture, which can cause blistering, poor adhesion or condensation within the build-up. Low temperature: adhesives, sealants, primers and resins cure slowly or not at all when it is cold, and some become stiff and hard to work. Wind: large sheets and membranes catch the wind, which makes handling and temporary fixing a safety matter.

Daylight matters in a different way. Short days mean fewer working hours, and a section that cannot be finished and made weathertight by dusk should not be started. The sensible approach is to work in smaller areas, close each one up before leaving and watch the forecast. We make no promises on programme, because the weather sets it, and the quote shows the likely effect on time rather than hiding it.

None of this stops winter work. It means the planning is more careful, and the choice of system more selective.

Mechanically fixed single-ply membranes are the most winter-friendly choice. The sheet is fixed through the laps with fasteners and plates, and the seams are welded with hot air in PVC and TPO or taped in EPDM, so there is little reliance on adhesive curing in the cold. The deck still needs to be dry, and the welding needs a dry seam, but a dry day in cold weather is workable. Our guide to single-ply membranes explains how each type is joined and fixed.

Metal sheet roofs also install well in cold weather. Sheets are fixed with screws, side laps are sealed with factory-applied or tape sealants, and the roof is weathertight as each sheet is laid. Cold makes sealant tapes less pliable, and the sheet maker's guidance on minimum temperature should be followed. Standing seam metal is closed with a seaming tool, not an adhesive.

These two groups suit the situation where a roof is failing and cannot wait for spring. What matters is a dry deck on the day of laying and a plan that closes each bay before the light goes.

Anything cured by chemistry or heat is more sensitive. Membranes stuck down with adhesive depend on the glue tacking at the right temperature; in the cold, contact adhesives can fail to grip properly and bubbles form later. GRP is a resin that needs a minimum temperature and a dry surface to cure, and a damp or frosted deck leaves it weak. Liquid-applied coatings behave the same way, and a coat that gets rained on or frosted before it cures can be wasted. Our page on liquid coatings on commercial roofs explains why those are better timed for spring or autumn.

Built-up felt is mixed. Torch-on layers can be laid in cold weather, but felt is stiffer and harder to handle, and the flame has to be managed around a cold, possibly damp deck. Cold-applied felt systems depend on adhesive curing, so they are less suited to the coldest weeks.

The material maker's data sheet sets the working limits for each product, and those limits take precedence over anything a roofer says on a bad day. If the limits cannot be met, the work waits.

On a stripping job, the key rule is never to leave the building exposed. The roof is taken off in sections no larger than the crew can close up in a day, and each section is covered with the new waterproof layer or a temporary membrane before they leave. Materials stay covered on site, away from standing water, and a stack of insulation boards left uncovered will take up moisture and spoil the roof they are laid on.

Existing insulation matters too. If it is wet, it comes out, since laying a new membrane on damp insulation will trap the moisture. A survey with moisture readings identifies this beforehand, and the written quote allows for replacing any wet insulation, so it does not arrive as a surprise on the day.

Where the building is trading, the protection underneath is as important as the cover above. See repairing a commercial roof while you trade for how that is organised.

The choice turns on how bad the roof is. If it is leaking into stock or machinery, winter is when it needs doing, and a cold-tolerant system should be chosen. If the roof is tired but holding, a planned spring or summer start gives wider choice of system and a more even programme. Our page on how long a commercial re-roof takes explains how the programme builds up.

A middle route is to make the roof safe now with a repair and plan the full replacement for a better season. That keeps the building dry and stops a small defect from becoming a large one. The survey tells you which route is realistic, with photographs of the roof and a view of the deck and the insulation.

Whichever way you go, the quote that follows is written, our workmanship guarantee runs for 10 years in writing, and you can see more about the wider service on our commercial roofing page.