The short answer
A straight replacement of one VELUX window, same size in the same opening, can often be done in a day, with the weather and the roof covering allowing. A new window in a roof that has none takes longer: cutting and trimming the rafters, forming the lining and plastering it are separate stages, and the finish needs time to dry before it is painted. So the roof can be closed in a day, but a finished room is a matter of days, and a promise of "fitted in a day" is worth reading carefully.
A replacement, the quick case
When the opening is already there, the work is a sequence that fits a day comfortably. The old window and its flashing come out, the new frame is set in the opening and fixed to the rafters, the new flashing is laid into the roof covering, and the sash goes in. The roof is weathered the same day, before the light goes, because an open roof overnight is not something anyone plans.
That day is for the roof side. What happens inside depends on how much the old frame disturbed the plaster and paint, and the survey is where we find out. A neat swap with a sound lining may only need a bead of sealant and a touch of paint. A frame that was bedded in filler and foam may mean making good the reveal, which can need a second visit to let it set. A single window is also easier to fit in a day if scaffolding is not needed, so access from inside the loft or a ladder matters.
A new opening, the longer case
Cutting a window into a roof that has none is a different order of work, and it runs over several days for a few reasons.
The roof covering has to be stripped back, a rafter or two cut and trimmed with new timbers, the frame fitted and flashed, and the roof made watertight. That is a structural alteration, notifiable to Building Control, and the trimming has to be sound before anything is closed up. Inside, the ceiling is opened, the lining frame is built to suit the depth of the roof, insulation is fitted behind it, and the lining is boarded and plastered or taped and jointed. Plaster needs time to go off before it can be painted, and a splayed lining takes longer than a straight one.
Our page on VELUX window installation sets out the full sequence for a new opening, and the guide to how a rooflight is finished inside covers the plastering stage.
What decides how long it takes
Four things move a job from one day to several.
- Replacement or new opening
- The biggest difference, as above.
- Number of windows
- Two windows side by side in a loft room are quicker per window than two on different roofs, but they are still two sets of flashing and two linings to finish.
- Roof covering and access
- Slate and plain tile are slower to cut around than large interlocking tiles. A steep roof or a tall house may need scaffolding, which has to be erected before the work starts and taken down after. The flashing family has to match the covering, and VELUX flashing kits explained shows how it is chosen.
- The state of the ceiling
- An old lath and plaster ceiling in a Georgian terrace needs careful opening and lime plaster that is built up in coats, which cannot be hurried. A modern plasterboard ceiling in a new build, as in Cranbrook, is simpler.
The weather, and why it can move a day
Roofs can only be opened in settled weather. In Devon, a forecast of heavy rain or strong wind can push a roof job back, because a roof that is open is not left to chance. We plan the day around the forecast and, where it turns, the roof is closed in or the job is moved. That is a decision made in the interest of the house, and it is better made on the morning than halfway through.
Dust, access and the room
A day of work in a lived-in house raises dust, and a good job plans for it. Furniture is moved or covered, the floor is protected, the opening is sheeted from the room and the work area is cleaned before we leave. A plastering stage creates more mess than a window swap, and the clean-up is part of the job, not an extra.
It is also worth clearing the space under the window before we arrive. A landing or a bedroom with a bed beneath the opening is much easier to work in empty, and it reduces the risk to your belongings.
Painting and the last day
Even a quick swap ends with the finishing, and it is the part people forget to ask about. New plaster or filler needs to dry before it takes paint, and a mist coat or sealer goes on before the topcoat so the colour does not flash. If the quote says the lining is left ready to paint, you have a dry, sound surface to decorate when you are ready. If it says painted, we return to put the finish on once it has dried. Either is a fair arrangement, as long as it is written down before the work starts and you are not left guessing which one you have bought.
A window that is fitted in a day but left with raw plaster and a pencil line is not finished, however quickly the roof was closed.
What to ask for in a quote
Ask how many days, split between roof and inside, and what state the room will be in at the end of each. Our written quote comes with a finish schedule that records how the lining is formed and what state the surfaces are left in, from bare plaster ready for your decorator to a finished coat. It also states the Building Control notification, which we handle, and the dust management. If you are replacing a whole window, can a VELUX window be replaced like for like explains what a swap involves.
To get started, ask for a quote with a photo of the room and the roof, and we will arrange a survey to give you an honest estimate of the time.