The short answer
Yes, for most ordinary houses. Under permitted development a rooflight can go in without a planning application if it does not stand more than 150mm proud of the original roof slope and does not rise above the highest part of the roof. Flats, listed buildings and homes with their rights removed are the exceptions, so check your own address first.
The two limits that decide it
Permitted development is a set of national rules that allow small changes to a house without asking the council. For roof glazing, two measurements matter.
The first is projection. A rooflight that sits in the plane of the roof, like a roof window in a pitched slope, or sits low on a flat roof, must not stand out more than 150mm from the surface of the original roof. That figure is measured from the roof as it was built, so a flush window in a tiled slope is well within it. A unit on a raised upstand is where the measurement starts to bite.
The second is height. No part of the alteration may be higher than the highest part of the existing roof, the ridge on a pitched house. That rules out anything that would poke above the ridge line, and it is rarely a problem for a window cut into a slope.
Both limits come from the general permitted development order for houses, in the class covering other roof alterations. They apply to a dwellinghouse, so they do not carry across to every building. For how these rules sit within the wider planning picture, see planning permission for rooflights and skylights.
Where the allowance does not reach
The rule is generous, but it has edges. A number of homes sit outside it, and it is worth knowing which before a design is drawn up.
- Flats and maisonettes. Householder permitted development rights do not extend to them, so a rooflight there normally needs an application, along with the freeholder's consent.
- Listed buildings. These need listed building consent for changes that affect their character, whatever the national rules say.
- Homes with rights removed. Some houses have had their permitted development rights taken away by an Article 4 direction, or by a condition on an earlier planning permission. New estates sometimes carry such conditions.
- Conservation areas. Extra care applies, especially to a roof slope facing the street, and the council may hold tighter rules for the area. We treat the position as checked for the address.
- Buildings that are not houses. Converted or commercial property falls under different rules.
The council holds the record of any removal, and it is quick to ask. Our page on whether Crawley Borough Council needs to approve a rooflight shows where to begin locally, and the conservation rooflight installation service covers homes where heritage rules apply.
Roof lanterns and the 150mm line
A roof lantern is a different object from a flat rooflight. It rises from the roof in a pitched shape, on an upstand, and its height matters.
The kerb, the bars and the ridge of a lantern together stand well above a flat pane. A lantern is normally taller than 150mm, so it is unlikely to sit inside the projection limit on its own. That does not mean a lantern needs a separate application every time. A lantern on a new extension is usually considered as part of the extension, which has its own permitted development limits on height, eaves and boundaries, or it is included in the planning application for the extension. The safe route is to show the lantern on the drawings and confirm how it is being treated before anything is ordered.
On an existing flat roof, a low, fixed flat rooflight is the simplest case. A walk-on unit set flush with the roof is covered in walk-on rooflight installation, and the flat options in flat roof rooflight installation. For the lantern itself, see roof lantern installation.
| Rooflight type | Usual position on the 150mm rule |
|---|---|
| Roof window in a slope | Sits within it |
| Low flat rooflight | Sits within it if the upstand is shallow |
| Roof lantern | Stands above it, so check |
| Sun tunnel dome | Low, but measure the dome |
Planning is one rule, Building Regulations is another
Being allowed without planning permission does not mean being free of other rules. They run side by side.
Building Regulations still apply to a new opening in the roof. Part L covers the thermal performance of the glazing, Part K covers safety glazing, and a new opening also raises questions of structure and fire spread. Where the work is notifiable, the Building Control notification is handled for you as part of our work. The two regimes are set out in Building Regulations for rooflights explained, and the question of sign-off is answered in does a new rooflight need Building Control sign-off.
A new opening in a roof may also need a structural check, because it interrupts rafters or joists. That is a separate question, covered in does a rooflight need a structural engineer.
Short answers on rooflight rights
Do I need a lawful development certificate?
It is optional. Some owners apply for one so they hold a written confirmation for a future sale. Ask the council how it handles them.
Can I fit a rooflight on the front slope?
On an ordinary house outside a conservation area, the same two limits apply at the front as at the back. In a conservation area, or where rights have been removed, check first.
Does replacing an existing rooflight need planning permission?
A like-for-like replacement in the same opening is usually a different question from adding a new one. Keeping the same size and projection keeps you inside the allowance, and our page on replacing an old skylight explains the options.
Who checks the planning position for my address?
We look at it when we survey, and the council has the final word on any doubt. Get a quote and we will note the points to confirm. The full service is on our skylight and rooflight installation page.