Timing answer
How long does fitting a skylight take?
The hours on the roof are only part of the timeline. This answer separates the fitting from the steps that come before it, and shows what stretches or shortens each.
The answer
A roof window going into a pitched roof is a short job on site, measured in days rather than weeks. A flat rooflight with a new upstand takes longer, and a lantern longer again. The wait before the fitting, for a survey, a made-to-measure order or planning permission on a flat, can outlast the work on the roof.
What decides how long the fitting itself takes?
Three things: an opening that is already there or a new one, the material on the roof, and the number of units. A swap into an existing opening is quicker than cutting a new one.
On the roof, three things set the pace. The first is whether the rafters or joists already have an opening of the right size. Replacing a unit in a sound opening involves less carpentry than creating one, because the structure has already been trimmed.
New opening or existing one
Making a new opening starts with lifting the covering, then cutting into the timbers, supporting them on trimmers and setting the frame. That is several trades' worth of steps in one place, and each has to be done in order.
The roof covering
Slate and plain tile are lifted by hand and relaid around the frame, which takes longer than working into a concrete tile or a bonded membrane. A flat roof needs its upstand built and the membrane dressed up it before the unit goes on.
How many units
Two roof windows side by side in a loft take longer than one, though not twice as long, since the scaffold or access, the loft clearing and the finishing are shared. Our survey adds up these factors for your roof, which is how we know whether yours is a short job or a longer one.
Why can the wait before fitting be longer than the fitting?
A survey, a quote, a made-to-measure order and, on a flat or a listed house, an application all come first. The fitting visit is the last step in a chain that can be longer than it.
Homeowners often ask about the work and forget the sequence around it. Each step before fitting day has its own pace, and a few of them depend on other people.
Survey and quote
The survey comes first and is free. We look at the house type, the roof and the room, and then send a fixed written quote. Taking the quote in and agreeing it is up to you.
Made to measure
Standard roof windows come in set sizes and can be ordered once the opening is decided. Flat rooflights and lanterns are generally built to the size of the opening, so they are ordered after the measurements are confirmed and arrive when the maker has finished them.
Permissions
A new rooflight on a flat needs planning permission from the council, and almost any rooflight on a listed house needs listed building consent. Both depend on the council's decision time, so we do not place the order until the answer is in. On a house within Class C, no application is needed, and the lead-up is shorter. The work is notified to Building Control in every case, and we deal with that where it applies.
| Job | Before fitting | On the roof |
|---|---|---|
| Roof window, existing opening | Standard size, ordered after survey | The shortest job |
| Roof window, new opening | Standard size; flat or listed homes wait for a decision | Short, with structural work |
| Flat rooflight | Made to measure after the survey | Longer: upstand and membrane |
| Roof lantern | Made to measure, longest wait | Longest: frame built up in stages |
| Sun tunnel | Standard kit, ordered after survey | Short: small roof opening |
What happens during the fitting visit?
First the covering is opened up, then the timbers are cut and propped on trimmers, and the frame goes in and is weathered before the lining inside. Each stage has to dry or set before the next, which is what shapes the schedule.
The visit follows a fixed order, because each stage supports the one after it.
Opening up
The roof covering is lifted around the position, and the rafters or joists are cut and supported with trimmers. On a flat roof the deck is cut and the upstand is built. This is the stage where the roof is most exposed.
Setting and weathering
The frame is fixed to the trimmed structure and the flashing or membrane is dressed into place. Pitched roofs get a flashing kit chosen for the slates or tiles. On a flat roof the membrane climbs the upstand and tucks beneath the frame. Only then is the glazed unit fitted and checked for operation.
Inside the room
Indoors, the shaft that links roof to ceiling gets its lining and finish last of all. Depending on the room, that means plaster, boarding or paint, and some of it needs time to cure before it is decorated.
Sign-off
The Building Control notification covers the work, and the written guarantee, ten years on the workmanship, is issued when the job is done. Both are described on our guarantee page.
What can add time once the job has started?
Wet or windy weather, a roof structure that differs from what the survey showed, and access to the loft or the roof. Where the job changes, the written quote changes with it.
Most of the variables are known before the first day, which is the point of surveying first. A few can still shift the schedule.
Weather
A roof is opened up for a fitting, so the work waits for conditions that suit it. Rain or strong wind can move a visit, particularly for large flat rooflights and lanterns, which are lifted into place.
What is under the covering
The survey looks at the roof from the loft and from outside, but the timbers around the position are only fully seen once the covering is lifted. If the structure differs from what the survey showed, the job has changed, and the price on the quote changes with it. We explain why before going on.
Access and the room
A loft full of belongings, or a room that cannot be cleared underneath the opening, slows the start. Telling us about this at the survey lets us plan the first hour properly.
For the full run of products and what goes with each, start from the main page; for pitched-roof windows in particular, see how sizes for loft rooms are worked out.
More on timing and booking
Does someone have to be in while the work goes on?
Access is needed to the room under the opening and to any loft above it. The arrangement is agreed beforehand, at the survey, so the day itself holds no surprises about who lets whom in.
Does a bigger unit take longer to fit?
Yes, because more covering is lifted, more structure is cut and a heavier unit has to be lifted into place. A wide flat rooflight is a longer visit than a small roof window, even on the same house.
Can fitting be done in winter?
Yes, with the forecast in mind. Cold alone does not stop the work, though rain, ice and wind can move a visit, and plaster or paint finishing takes longer to dry in cold weather.