Enlarge a roof by adding a dormer

Last updated: 26 February 2018

If you want to add extra space to the top floor of your house, you might want to consider adding a dormer.

A dormer is an extension, usually with a window, that sticks out of a sloping roof and gives you a bit more headroom.

Permitted development

Before you arrange to have a dormer added to your roof, you should first check to see if you need to apply for planning permission.

Most dormers don't need a planning permission application, because most meet a set of rules called 'permitted development'. The permitted development rules for dormers are:

  • they aren't on a side of your house that's facing a road
  • the distance between the dormers and the boundary they face is more than 10 metres
  • the development would not make your house taller than it already is
  • they aren't taller than your house (measure at the eaves line)
  • all your dormers combined cover less than half the roof
  • the distance between the dormers and the edge of the roof is at least 30 centimetres
  • it isn't within a conservation area

You should always check with your council's planning department to see whether you need to apply for planning permission. Even if you meet the permitted development rules, there may be other approvals you'll need to get.

For a more detailed explanation of what's considered a permitted development when adding a dormer to your roof, read the Scottish Government's Guidance on Householder Permitted Development rights publication and go to section 4.42.

Planning permission

If you want to build a dormer but it doesn't meet the conditions for permitted development, you have to apply for planning permission.

Find out how to apply for planning permission, or contact your local council for further information.

Other approvals

You might need other approvals before you can carry out work. For example, you might need approval under the building regulations from the local council.

If you don't own the land on which the development is being carried out (for example, if you're a tenant or the land's in joint ownership), you may need to get the landowner's permission.

If you live in a listed building you will probably also need to obtain listed building consent.

It's your responsibility to make sure you get any necessary approval.