How long does it take to fit a roof window?

When a new roof window goes into the opening of an old one, the framing is already there. The job is to lift the surrounding tiles or slates, remove the old frame and flashing, check the timbers for damp or rot, fit the new window and flashing kit, and relay the covering. In that case the roof is open for a short time and it can be sealed up before the day ends.

Even then, the old unit sometimes holds a surprise. A leak that has been there for some years may have softened the timber at the head or sill of the opening, and rotten wood has to be cut out and replaced. A flashing built into a stone or slate covering may need the surrounding courses re-laid, which takes longer than a cut-and-fit job in plain tiles. We photograph the opening at the survey where we can, and a repair to the framing is flagged in your quote, so the extra work is visible. A rotten sill timber found at that stage is replaced before the new frame goes in, since fitting a new window onto a weak surround only hides the problem for a few winters.

If you suspect that your window is leaking, our guide to roof windows and skylights explains how we survey one.

A new opening takes more steps in a set order. The covering is stripped back from the area, the rafters are marked and cut, and trimmers, short timbers fitted across the opening, take the load from any cut rafter. The roof window is then installed with its flashing and the covering is cut and laid back around it.

Inside the loft, the opening needs lining so that it reads as a finished reveal, with insulation fitted around the frame, a vapour control layer and plasterboard. Skilled plastering follows, then decorating. The time is spread over trades and drying periods, which is why we plan the roof work and the finishing in sequence and say so in the quote. The roof can be made weathertight early; the plaster and paint come later.

Ask early how many separate visits the plan needs, because a job with plastering and decorating has gaps between trades that a roof-only swap does not. The more windows in the job, the more the programme depends on staging and materials. A pair of windows in the same slope is quicker per window than two jobs on two slopes, because the scaffold, stripping and covering work are shared.

Weather comes first. If rain is forecast we would rather move the date than open a roof, and temporary sheeting is the fallback, not the plan. Starting times are a judgement made nearer the day, and no hour is promised.

Access is second. A house on a steep Stroud lane or terrace with no room for a tower or a delivery vehicle, adds handling time. A long carry up a hillside path for windows, timber and materials takes longer than a driveway. We note these on the survey so they are priced and planned in advance and do not turn up on the morning.

Materials are third. A window in a standard size is on the shelf; an unusual size or finish can take weeks to arrive. Natural stone slates or old clay tiles around the opening may need matching, and sourcing them is a lead-time question as well as a cost one. Ordering ahead helps, because a window that arrives after the roof is opened leaves the weathering to temporary cover, so we confirm delivery before any stripping begins. Our answer on roof windows in a conservation area covers when consents might add time before any work starts.

The window is not finished until the inside is. The reveal, which is the sloping lining around the opening, must be insulated and plastered or boarded. The sill, the paint, the blind and any electrical connection for an electric window are the last steps. Plaster needs time to dry before decoration, and that wait is a feature of the trade rather than a delay on the roof. If a loft room is being converted at the same time, the window is only one item in a larger programme of floors, stairs, insulation and electrics.

For a window that is being fitted from the inside, with no scaffold outside, the internal sequence is similar but the access plan differs; our answer on fitting a roof window from inside explains when that works.

When the work is done, the rubbish goes with us and the site is left tidy. A 10-year workmanship guarantee, in writing, covers the installation.

Time and cost are linked, because labour is most of what you pay for. MyBuilder's 2026 guide puts installation of a standard roof window at £350 to £600, with scaffold at about £500; those are national ranges and do not describe our own pricing. Our guide to roof window costs goes through what pushes a job above or below them.

Following the survey comes a quote that covers scaffold, window, structural timber, covering work and making good, with the expected programme alongside. Should weather or a decayed rafter alter the plan, you hear about it before the work changes, not after.