Can a roof window be fitted from inside?

1What is done from inside the house

Inside the roof space is where a good deal of the careful work happens. The position of the window is marked out from below, so the opening lines up with the room rather than with a guess from the roof. Insulation is cut back, the rafters are measured and, where one has to be cut, the trimmers that carry its load are fitted from inside.

Once the frame is in, the finishing is done from below as well: the lining of the reveal, the insulation around the frame, the plastering and the decorating. A well-done lining makes the difference between a window that looks part of the room and one that looks like an afterthought.

So when people ask about fitting without scaffolding, they are often really asking how much can be kept off the outside. The inside work is a good part of the job, but it is one part.

2What cannot be done from inside

A roof window is sealed to the roof at the covering. Tiles or slates near the opening must be lifted, the battens cut and the frame screwed down to the rafters from above. The flashing kit, the metal surround that steers water past the frame, is then layered in with each course of the covering. None of that can be reached from the loft.

Consider too what happens when a step is missed. Water that gets past an unfinished flashing runs down the underside of the roof, not away from it. For that reason we never suggest a window can be fitted without touching the roof at all. It cannot, and any claim that it can deserves a second look.

Our answer on how long a roof window takes to fit sets out these stages and why the weather matters for each.

3How the roof is reached

Access is decided by the building, not by preference. On a low roof, such as a bungalow or a rear extension, a hooked roof ladder and a crawling board to spread the weight may be workable. A taller house is different: scaffold supplies a platform with edge protection, and somewhere to land materials.

The covering matters too. Slate and old clay tiles are brittle, and walking over them breaks them, so a slate roof usually needs a platform or boards rather than someone treading across the slope. We cover slate specifically in fitting a roof window in a slate roof.

We judge this at the survey from the eaves height, the covering, the position of the window on the slope and the ground below. If a method is unsafe, we rule it out, and the quote reflects the access the roof actually needs. Our skylights and roof windows page shows the wider range of this work.

4Scaffold on the highway needs a licence

Section 169 of the Highways Act 1980 bars anyone from putting up scaffolding that obstructs a highway without written authority from the highway authority. Across Worthing and Adur that body is West Sussex County Council, and it needs 10 working days' notice before the scaffold goes up. The scaffold firm makes the application, not the householder. Brighton and Hove runs a separate licence of its own through the city council.

That wait can dictate the start date more than the window does. Scaffold standing wholly on your own drive or in a back garden is not on the highway, so the licence question does not arise in the same way. A scaffold that spans a front path onto the pavement does.

MyBuilder's roof-window guide, updated on 21/08/2026, gives scaffolding as approximately £500 for a window job as a typical UK figure. The cost of yours depends on the house, the sides that need covering and how long it stands; the written quote follows the survey.

5Deciding whether it is worth it

If you want to keep the outside work to a minimum, the best options are a window on a low, accessible slope, a like-for-like swap into an opening that is already framed, or a position near the eaves. A window high on a tall roof is unlikely to avoid scaffold safely, and a position over a porch or bay adds its own complications for placing ladders and boards.

It also helps to clear the loft below the window position before the day, so the team can work from inside without carrying stored items out of the way first.

A walk-on rooflight in a flat roof is a different kind of job, because the work is done from above on a level surface. Our answer on walk-on rooflights goes through those.

For the cost side, see roof window cost. We show photographs of your roof with the written quote, one total price, so the access decision is visible rather than assumed.