Do I need planning permission to put a window in my roof?

A roof window on a house in England is usually permitted development under the roof alterations class of the General Permitted Development Order (GPDO 2015, Schedule 2, Part 1, Class C). The window must meet three conditions:

• it stands out from the roof slope by no more than 150mm
• it does not rise above the highest point of the roof
• any window in a side-facing roof slope is obscure-glazed, and non-opening below 1.7m above the floor

A flush-fitting roof window sits close to the slates, which helps it pass the projection test. We check the projection against the maker's figures before we order the window. The wider rules are gathered in the guide to wider planning and Building Regulations rules.

Apart from the side-slope condition, the permitted development test does not depend on which slope the window is in, so a roof window in a front slope that passes the three conditions is covered. The street view becomes a planning matter where an Article 4 direction applies, covered below.

Three cases sit outside the rule:

• Flats and maisonettes. Class C does not reach them, so a roof window in a flat usually needs the council's permission; ask the council first.
• Listed buildings. A new rooflight on a listed building cannot go in without listed building consent, whatever the permitted development rules allow, and the guidance on consent for a rooflight on a listed home explains the application.
• Houses with their rights removed. Some conditions on an earlier planning permission can take away permitted development, so the planning history of a newer estate is worth checking.

Some Leeds terraces and villas sit in conservation areas, and in some, an Article 4 direction withdraws those rights. Where one applies to your street, a roof window in the front slope may need an application; some directions cover only the slopes that face a road. Leeds City Council holds the list of areas and directions.

What the council looks for in these streets is set out in conservation-area rooflights in Leeds. We look up the planning status of your street before ordering the window, so the window on the quote suits the rules for your street.

Before ordering, we hold the address up against the points above. We ask whether the house is a flat, a listed building or inside a conservation area, whether an Article 4 direction applies, and which slope the window will sit in. We also check the projection figure on the window we propose against the 150mm limit and the ridge height.

Where no application is needed, the window goes ahead under permitted development. Where an application is needed, we say so at the start and the order waits for the council's decision. Leeds City Council is the planning authority for addresses in the city, and a town outside it has its own council, whose planning service answers for that address.

A householder can ask the council for a lawful development certificate, a written confirmation that the work is lawful. The certificate is optional, and it gives you a record to show a buyer later, which can save questions when the house is sold. A landing window over the stairs is a common job where the question comes up, and lighting a landing or stairwell shows where it sits in the slope.

Permitted development covers planning only. A new opening in the roof frame is structural work under Approved Document A, and it is notifiable building work. Replacing a roof window is notifiable too, with the energy standard of Approved Document L: Table 4.2 sets a U-value of 1.4 W/m²K, or Window Energy Rating band B, for a roof window. We handle the Building Control notification, which goes to the local authority or a registered building control approver.

The two checks are answered by different bodies, so a window can pass one and still need the other. The paperwork is part of the job, and the cost of fitting a roof window covers how it figures in the price.