Can rooflights be fitted in winter?

The short answer

Yes, and it happens throughout the Gloucestershire winter. What changes between June and January is not whether the work is possible but how the day is planned around it. The governing rule is the same in both seasons: the roof is never left open overnight, so an opening is only started when it can be closed and made watertight the same day. In December that day is shorter, the weather turns faster, and a few materials behave differently in the cold, so the sequence tightens and the margin for a late start disappears. Nothing about a winter installation is a compromise on the detailing. It is a compromise on the amount that can be attempted between first light and dusk. What happens on the day itself is on what happens on installation day.

Closing the roof every evening, which decides everything else

The whole winter method follows from one commitment. An opening is formed, trimmed, the unit set, fixed and flashed, and the covering re-laid into the flashings before the crew leaves. Where a job cannot reach that point in the light available, the outside work is not started that morning.

On a straightforward roof window in an accessible pitch that is comfortably achievable in a winter day, with the reveal, insulation and plaster following on a second day inside the house where the weather is irrelevant. Where several units are going into one slope, the sequence runs from the top of the slope downwards, so every evening ends with a whole roof rather than a temporary covering. On a lantern with structural work the deck is sheeted and weathered at the end of each day, and the programme is written on the assumption that it will be.

Eight hours of daylight, and what fits inside them

At the end of December, Gloucester gets light at around a quarter past eight and loses it a little after four. Usable working light on a roof is shorter than that at both ends, because early and late sun is flat and low and a wet slate is genuinely hard to read.

So a winter start is early, the materials are on site the day before rather than arriving at nine, and the scaffold or tower goes up as a separate visit rather than eating the first two hours. One unit a day is the realistic figure on a pitched roof in January where two might go in during July. That is a scheduling fact rather than a price one, and it is why winter dates are quoted with fewer units per day rather than with a longer overall programme.

Rain, and the difference between working in it and opening in it

Roofers work in light rain all the time. Stripping a covering, setting a frame and dressing lead are all possible with water about. What is not sensible is having a hole in a roof over an occupied room while rain is coming in, and what is not possible at all is bedding anything that needs a dry surface.

The practical rule is that the forecast decides the morning. Where a settled window of several hours exists, the opening goes ahead. Where the forecast turns during the day, the outside work stops at a point where the roof is whole, which may mean the frame is in and flashed with the internal work deferred. The Severn Vale gets a lot of grey drizzle between November and February and very little of it stops work. Heavy sustained rain does, and that is a call made in the morning rather than at eleven o’clock with the covering already off.

Wind, which stops a job long before rain does

Wind is the real limiting factor and it is underestimated by everyone except the people on the scaffold. Handling a sheet of glass, a large flat unit or a length of lead in a gusting wind is dangerous, and the load on a person holding a flat object at height rises very steeply with wind speed.

Around gale force the work stops entirely, and glass handling is usually curtailed well before that. Gloucestershire’s weather arrives from the south west with force behind it, and the exposed places are exposed: the tops of the wolds catch everything, the Forest of Dean is wetter and windier than the vale, and a Stroud valley funnels it into something worse than the forecast suggests. A February gale is the most common reason a winter date moves, and it moves by days rather than weeks.

Frost and ice, on the covering and underfoot

A frosted slate roof is a surface nobody works on. It is slippery in a way that a wet one is not, and the fragile places on an old covering are hidden under white. On a hard frost the outside work waits until the roof has cleared, which on a north facing slope in the Forest can be late morning.

Scaffold boards ice over as well, and edge protection that is perfectly adequate in July needs looking at again when everything is glazed with frost. None of this stops January work. It shifts the start time and it takes an hour out of the day, and an honest winter programme has that hour in it rather than discovering it on site.

Materials in the cold, and the ones that care

Most of the job is mechanical fixing and overlapping, which is indifferent to temperature. That is one of the underrated virtues of a properly detailed rooflight: nothing relies on adhesion, and every joint is a lap running in the direction the water is already travelling.

Lead works cold, but it is less forgiving when it is very cold and it is dressed more slowly and more patiently to avoid splitting at a corner.
Sealants and adhesives generally have a minimum application temperature of around 5 degrees, and cure slowly below that. Where any are used they go on to a dry, clean surface or they wait.
Mortar is not laid in frost or when the temperature is falling towards it, which matters on a stone slate roof where bedding is part of the detail.
Plaster needs warmth and air movement to dry. A reveal skimmed in an unheated loft in January takes considerably longer before it can be decorated, and rushing it with a heater against the wall causes cracking.

Getting there, which is a winter problem of its own

Access changes in Gloucestershire between seasons more than the roof work does. The vale lanes around Maisemore, Ashleworth, Frampton and Twyning flood and stay soft for weeks, and a scaffold lorry on a saturated verge is a recovery vehicle waiting to happen. The valley approaches at Chalford, Bisley and Rodborough are steep, narrow and frequently sheeted with ice on a north facing bend.

Where material has to be hand carried in, doing it in the dark and the wet is slower and more hazardous, so those jobs get the early slot in the day and the better half of the week. This is looked at during the survey rather than on the morning, and a winter date for a valley address is set with the lane in mind.

Snow, and the days that are genuinely lost

Lying snow stops roof work. It hides the covering, it makes every surface unsafe, and clearing it off a slope to work is neither quick nor sensible. Gloucestershire gets few of these days in a typical winter, more of them on the wolds above Northleach and Stow than in the city, and they are usually short lived.

The way that is handled is with float in the programme rather than with optimism. A winter date carries a fallback date, the internal work is arranged so it can proceed on a day the roof cannot, and nothing is promised for a specific morning that depends on the weather cooperating.

Why winter is frequently the better time to book

Three reasons, and they are practical rather than promotional. Lead times through the trade are shorter between November and February than they are in spring, so a survey turns into a date faster. Scaffold is easier to get hold of. And the case for the work is at its clearest in the season it is meant to solve, because a dark room in a Gloucester terrace is at its darkest in January and the difference a rooflight makes is obvious immediately rather than in six months.

There is also the argument for not waiting. A unit that has already misted, or a frame with perished gaskets whistling in a gale, is not improved by another winter. Replacing an existing unit follows slightly different rules because the opening is already there, and that is on replacing a rooflight in winter. Booking lead times are on how far in advance to book, and the work itself on the skylight and rooflight installation page.