Question answered
Can you add a roof window to a top-floor flat?
The short answer
You can sometimes add a roof window to a top-floor flat, but you cannot assume the house rules apply. Part 1 of the permitted development order covers dwellinghouses, and the order says a dwellinghouse does not include a flat or a building containing flats. So a flat needs planning permission, and as the roof is normally owned or managed by someone else, you also need the freeholder's written consent.
Sometimes, but not on the same footing as a house. A flat has no householder permitted development rights, and the roof above you is usually not yours alone, so two permissions come before any fitting date.
Why a flat is treated differently from a house
The householder rights that let a house owner fit a roof window without an application sit in Part 1 of Schedule 2 to the General Permitted Development Order 2015. They apply to a "dwellinghouse", and the order's own definition excludes any building containing flats and any single flat within one.
The result is simple to state. Class C, the class that covers other alterations to a roof, is not available to a flat. A conversion of a house into flats loses the rights too. If your flat sits in a converted Victorian villa or a purpose-built block, the same position holds.
The legislation website lists amendments to this part of the order that are not yet applied, so get the current position confirmed by the planners before you rely on this page. Ask them in writing, and keep the reply.
What that means for a planning application
Without permitted development rights, a roof window in a flat generally needs a planning application. In Worthing and Adur you apply to Adur & Worthing Councils, where one team at Worthing Town Hall serves two separate planning authorities. For a flat in the National Park, the Park authority is the planning authority.
The application is usually modest. A drawing showing the position and size of the window, the make and the roof covering is the sort of thing the planners look at. A window on a rear slope that nobody sees from the street is a very different case from one on a front slope in a conservation area, where appearance carries real weight.
Listed buildings are a further layer, since alterations that change a listed building's character need listed building consent too. Some seafront Victorian blocks in Worthing and Brighton sit in conservation areas, so check early. Our skylights and roof windows page shows the wider work we do.
The freeholder, the lease and the roof
Planning permission does not give you the right to cut into the building. In most flats the roof, the roof structure and the walls are not part of what you own. The lease usually keeps them under the freeholder or a management company, and it normally forbids structural alterations without consent.
That is why the first call is often to the managing agent. Ask for the lease clause on alterations and the process they follow. Expect to be asked for drawings, the make of window, the name of the contractor and sometimes a fee. Some freeholders refuse a window outright because it breaks a roof they are responsible for keeping watertight.
A top-floor flat in a shared building also raises practical issues. Work from inside means scaffold or access over the roof, which affects every neighbour. Get consent in writing, and do not order the window until you have it.
Can the loft above you be used at all?
Many top-floor flats have no loft you can enter at all. The ceiling may be directly under the roof structure, or the space above may belong to the building as a whole and hold water tanks or services. A window needs a place to go: a clear opening between rafters, room for the shaft that carries light down to your ceiling, and a way to finish the lining.
That gives a surveyor plenty to check. We look at the rafters, the insulation, the covering around the opening and any wiring or pipework above your ceiling. If a conventional window cannot be made to fit, a narrow light pipe is sometimes easier, though it gives no view.
A listed or conservation-area building may call for a slim-profile window, described on the conservation rooflights page.
Who fits it, and what it costs
A roofer fits the window and the flashing, and a plasterer and decorator finish the lining. Whoever does the roof work should be able to explain how the opening will be made weathertight and who is responsible if it leaks later. Our page on whether roofers fit Velux windows sets out what that job covers.
MyBuilder's roof window cost guide (updated 21 August 2026) gives a typical UK range of £350 to £600 for a standard installation, with scaffolding at approximately £500. In a block, scaffold or access arrangements often change the sum, and the freeholder may set conditions on the contractor.
After a survey with photographs, our written quote gives one total price. Send us the lease clause, the freeholder's reply and a picture taken from the street. If you are still weighing up the options, compare the cost against that of a rooflight of the same size.
Roof windows in flats: two more questions
Do I need planning permission if the window is on the back of the building?
Yes, because the house rights do not reach a flat. A back slope is less likely to draw objections than a front one, but the application is still needed, and the freeholder's consent is needed whatever the planners decide.
What if the freeholder says no?
Then you have no right to cut into the roof, and planning permission alone will not change that. You could ask what their objection is and whether a different position or a smaller window would be accepted, or look at light solutions that do not touch the roof.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
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