Last edited 27 Apr 2021


Windows are openings fitted with glass to admit light and allow people to see out. They are often openable to allow ventilation. Rooflights (sometimes described as ‘roof lights’ or ‘skylights’) are windows built into the roof of a building.

Approved Document B2, ‘Fire safety: Buildings other than dwellinghouses’, defines a rooflight as:

A dome light, lantern light, skylight, ridge light, glazed barrel vault or other element to admit daylight through a roof.
Lantern roof light.jpg Rooflight.JPG

Rooflights are effective at allowing natural light deep into the centre of a building, particularly where it is not possible to install windows in perimeter walls or where privacy is needed. Where they are openable, they can also be effective at promoting natural ventilation, as they tend to be at the top of buildings and so can benefit from the stack effect. They may also be used to allow access to roofs or to roof terraces.

Some rooflights however can be seen as a poor design solution, contributing little to the architectural form of a building, and simply creating a hole in a roof because without them there would be insufficient natural light. They can also suffer from ponding, dirt accumulation and staining.

Rooflights must have safety glazing, and if they are out of reach, may need a mechanism or motor to open them.

In some areas, some rooflights may be considered a permitted developments, not requiring planning permission. However, it is sensible to consult with the local planning authority to check this.

BS EN 14351-1 (Windows and doors. Product standard, performance characteristics. Windows and external pedestrian doorsets) suggests that the term ‘roof window’ refers to a window that is in the same plane as the surrounding roof, and has a minimum pitch of 15 degrees. This is as opposed to 'rooflights' which by this definition are installed on an upstand, and so are not in the same plane as the surrounding roof.


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