How long does it take to fit a roof window?

Exchanging a window for a new one of matching size means the opening already exists, the rafters are already trimmed, and the lining is largely in place. The work is to take off the flashing, lift the old window out, set the new one, fit the new flashing and make good inside the reveal.

This is the fastest version, and it is often done in a single visit. The things that slow it are surprises: rotten timber around the old frame, flashing that does not match what is left of the roof covering, or a replacement whose dimensions differ slightly from the unit it replaces. A survey picks most of these up beforehand.

Where the old window is a different make or an obsolete size, a lining adjustment may be needed, and that adds time. Our page on roof window replacement explains when to swap and when to repair.

Cutting a new opening is a staged job. First the covering is lifted away, then the opening is marked and cut, rafters trimmed with new timber, the window set, the flashing dressed over the tiles or slates, and then the inside is lined and insulated. Each stage has to finish before the next can start, and the roof must be left watertight at the end of each working period.

That sequence is why a new opening takes noticeably longer than a swap. Where several windows are going in, the work can be arranged so the roof is only open in one place at a time. The job is modest beside a re-roof, but the care required is higher than people expect. Our page on whether a roof window fits any roof shows what we check first.

A wet spell can postpone the roof work by a day or two, and good firms do not open a roof in the face of a forecast. If your loft is full of belongings, clearing the area under the opening before the day makes a real difference to the speed and the tidiness of the work.

Building control inspections, where needed, can set milestones for the programme, such as inspecting the trimmed opening before it is closed up.

Two practical points help you plan. First, ask for the expected stages, not only a single date, because a job with a delivery wait looks very different from one using stock in hand. Second, keep some slack for the interior finishing, which is where most overruns on small projects happen. A realistic plan is better than an optimistic one.

Several things stretch the timetable. Access is one: a high or steep roof may need scaffolding to be put up first, and MyBuilder's roof window guide of August 2026 puts scaffolding at around £500 for a typical job. Weather is another, because covering stripped from a roof cannot be left open to rain.

The roof covering counts. Plain tiles and slate take longer to lift and relay than interlocking tiles. Natural stone slate takes longer again. Older roofs may also reveal rot or poor timbers once opened, which means repairs before the window can go in.

Some windows are made to order, with a wait before delivery. Special glazing, such as obscure glass, may take longer; see roof window obscure glass for the choices.

The window may be in within a day or so, but the room is not finished until the lining is plastered or boarded and decorated. Plaster has to dry before paint, which stretches the overall time. If you are having electric or solar windows, wiring comes first; see electric roof windows.

Many people plan the roof work first and the decoration afterwards, so the roof team and the decorator do not meet on site. That keeps dust off fresh paint and keeps the roof job on schedule.

Some of the time is spent before anyone arrives on site. Forming a fresh opening in a pitched roof alters the structure, so Building Regulations approval comes into it, and a replacement window must reach 1.4 W/m²K or earn Window Energy Rating Band B. Where approval is needed we walk you through it and deal with the notification to building control. See our page on roof window Building Regulations for the detail.

Listed buildings and some conservation areas need consent first, and that can take weeks. Starting with the consent question avoids a stalled job.

We survey the roof and photograph it, then give you a written quote and a plan of the stages. We aim to leave the roof weathertight whenever we stop for the day, and once the work is done the debris goes with us and the site is left clear.

On the day, expect noise and some dust while the covering comes off and the opening is cut, and expect access to the loft or the room below to be needed. We lay protection down inside before starting, and we ask you to move anything fragile from the area beforehand. After that the work is quieter, as the frame is set, the flashing is dressed and the lining goes in.

If you are choosing between options, the alternatives to a skylight can differ a lot in timescale, so it helps to compare them. You can reach us on 01793 626096, by WhatsApp or through the form. Our skylights and roof windows page has more.