The short answer for a typical house in England is no, you do not need planning permission to fit a roof window, provided the work stays inside the limits that Parliament set for permitted development. Those limits are tight, though, and several kinds of property are outside them completely. Planning permission is also only one of the permissions that a roof window can require, because Building Regulations, listed building consent and, in some cases, the lease on a flat each run on their own tracks. This page explains the planning rules in plain terms. It applies to England; Wales, Scotland and Northern Ireland have their own systems. It is general guidance, not legal advice, and the final word on your property belongs to your council's planning team.
What permitted development means
Planning permission is normally needed for building work, but central government has granted a long list of smaller projects a blanket permission, so that homeowners do not have to apply. That blanket is called permitted development, and it comes from a statutory order, the General Permitted Development Order 2015. The part that deals with alterations to a roof of a house is Schedule 2, Part 1, Class C, which covers any other alteration to the roof of a dwellinghouse. A roof window is exactly that kind of alteration. You can read the legislation at legislation.gov.uk.
If your project meets the conditions of Class C, planning permission is automatically granted and you do not need to apply. If it does not, you have to make an ordinary planning application, which the council decides on its merits.
The limits that apply to roof windows
For a roof window under Class C, three limits matter most:
- Projection. The window may stand no more than 150 mm out from the plane of the existing roof slope. This is why a flush-fitting window passes, and a bulky one with a deep curb may not.
- Height. No part of the alteration may be higher than the highest part of the existing roof. A window cannot poke above the ridge.
- Side-facing windows. Any window in a wall or roof slope that faces the side of the house, such as the side of a dormer or a hipped end, must be obscure-glazed. If it opens, the opening part must be more than 1.7 metres above the floor of the room.
The rules cover windows set into the slope. Other roof alterations, such as dormers, raising the ridge, adding a balcony or changing the roof shape, are covered by different classes and tighter limits, and usually need a separate look. A dormer is not a roof window in planning terms, and a loft conversion with a dormer should be checked on its own. Our page on roof windows for loft conversions deals with the escape and layout issues for a converted loft.
Where permitted development does not apply
Several kinds of property fall outside Class C, so the order does not give you the blanket permission:
- Flats and maisonettes. Permitted development rights for houses do not extend to flats, so a flat needs a planning application, and may also need the freeholder's consent under the lease.
- Listed buildings. Permitted development is restricted for listed properties, and listed building consent is required for work that affects the character of the building. A new opening in a listed roof nearly always needs it.
- Conservation areas. Class C is restricted here, in particular for alterations to a roof slope that fronts a highway, so a window on a street-facing slope can need permission.
- Article 4 areas. A council can remove permitted development rights in a defined area through an Article 4 direction. Your council's planning team can tell you whether you are in one.
- Homes whose rights have been removed. Some modern estates were built with conditions attached to the original planning permission that remove permitted development rights, so check your deeds or ask the council.
If your house is a period property, take a look at our pages on conservation rooflights, roof work in a conservation area and roof work on a listed building.
How to find out for certain
You have three routes. The first is to ask the planning team at your council, which is Basingstoke and Deane, Hart, Test Valley, Winchester or one of the neighbouring authorities depending on where you live. Many councils answer simple queries by email or phone, and some charge for formal pre-application advice. The second is a lawful development certificate, which you apply for to the council to confirm that a proposed project is permitted development. The certificate is a legal document, useful when you sell, and the application needs plans and a short description. The third is the Planning Portal at planningportal.co.uk, which has an interactive guide to common projects, including roof windows.
Whichever route you choose, give the council your address, the size and position of the window and the type of roof. Photographs help. The council can also tell you whether your road falls in a conservation area or is covered by an Article 4 direction, which affects the answer.
A worked example: three houses, three answers
Take a 1990s detached house on an estate with no conservation area. The owner wants a window in the rear slope of the loft to light a study. The window will lie flat in the tiles, its frame sits well inside 150 mm, and it does not rise towards the ridge. That is permitted development, and the only formal step is the building control side. Now take a Victorian terrace in a conservation area, where the same owner wants the same window on the front slope facing the street. Class C is restricted there, so the council has to be asked, and the answer may be that the front is refused and the rear is acceptable. Last, take a first-floor flat in a converted house. Permitted development rights for houses do not cover it, so the owner needs a planning application, the freeholder's consent and the building control checks, and may be told that the roof is not theirs to alter at all.
The same window is therefore three different questions. That is why we say to start with the address and the type of property, not the product. It also explains why online answers contradict each other: one writer is thinking of a detached house, another of a listed cottage. Treat any general rule, including this page, as a starting point, and ask the council about your own address.
Building Regulations are a separate system
Even where planning permission is not needed, a roof window usually is covered by the Building Regulations. Cutting an opening in a roof alters the structure, so a trimmer must carry the cut rafters. A new window is a thermal element, so it has to meet the energy standard. If the window lights a habitable loft room, fire escape rules apply. The details, including the Part L energy figures and the limit on using a roof window as an escape from an upper floor, are in our guide on roof windows and Building Regulations. A common misunderstanding is that permitted development means no paperwork at all. It means no planning application, and the building control side stays.
Other permissions that catch people out
A lease may forbid alterations to the roof, or it may require consent from the freeholder even when the roof is yours in practice. A mortgage lender may want to be told about structural works. A neighbouring property can be affected if the work involves a party wall, a parapet or a shared roof structure, in which case the Party Wall etc. Act can apply, and a professional can advise. A new window that looks into a neighbour's garden does not need their consent, but being open with them early saves bad feeling. Bats and nesting birds, which are protected, may be present in an old roof, and work may need timing or a survey first.
If you have already fitted a window without checking
It happens. A previous owner may have added a roof window years ago, and now a buyer's solicitor asks for the paperwork. If the window was permitted development, no planning paperwork exists, and a lawful development certificate can confirm that after the event. If building control approval was needed and never sought, the council can be asked about regularisation, a process in which the work is inspected, sometimes by opening up the lining and the roof, and a certificate issued if it passes. If the window went into a listed house, or into a street with conservation status, and no consent was given, speak to the council promptly, because enforcement action for listed buildings is serious and time does not make it go away. A roofer can inspect the window, the trimming and the flashing and report on their condition, which helps any discussion with the council.
What it costs and who does what
Planning application fees for householder applications are set nationally, and a lawful development certificate has its own fee, both published on the Planning Portal. For the work itself, typical UK ranges for a centre-pivot roof window supplied and fitted run from £680 to £1,300 in one trade guide, with manufacturer figures of £1,623 to replace an existing unit and £1,906 to add a new one, including VAT. What you pay depends on the covering, the position and any structural work, so your fixed quote follows the survey.
At our survey we look at the roof, discuss where a window could go and tell you if the plan looks likely to run into planning. Where building control is needed, we deal with that side of the work. The planning question is for you and your council, and we are glad to give photographs and measurements to support it. Related reading includes whether you can put a roof window in any roof and roof window types. Our roof windows page has the full list of services, and our number is 01256 213956.
