Loft conversions and roof extensions and planning permission

You can use our new tool to check if your project needs planning permission.

Flats

You must apply for full planning permission to do a loft conversion which includes any external alterations to the roof.

If your flat is a listed building or part of, you must apply for listed building consent for loft conversions.

If your loft conversion plans include installing a roof light, you must apply for householder planning permission if:

it would protrude more than 15cm above the roof slope. This is when measured perpendicularly from the external surface of the roof
the highest part of any roof light will be higher than the highest part of the original roof
it would include the installation, alteration or replacement of a microwave antenna, chimney, flue or soil and vent pipe
any new window in a roof slope forming a side elevation would be clear-glazed and openable. This is if the opening part is less than 1.7m above the floor level of the room to which it is installed
your property is covered by an Article 4 Direction and it will be installed on the front roof slope, or side roof slope if that faces the road.

If your loft conversion plans include installing a dormer window, you must apply for householder planning permission if:

your property is in a conservation area;
it will be installed on the front roof slope
the highest part of the dormer will be higher than the highest part of the original roof
on a terraced house, the size of the dormer would exceed the original roof space by 40m³
on any other house, the size of the dormer would exceed the original roof space by 50m³
the edge of the dormer closest to the eaves of the original roof shall, so far as is practical, be not less than 20cm from the eaves, measured along the roof slope from the outside edge of the eaves. This is other than in the case of a hip-to-gable enlargement
it would include installing, altering or replacing of a microwave antenna, chimney, flue or soil and vent pipe
it would include a balcony, veranda or raised platform
the materials would differ in appearance to those of the existing house; or
any new window located in a roof slope forming a side elevation would be clear-glazed and openable if the opening part is less than 1.7m above the floor level of the room to which it is installed.

If your house is a listed building you must apply for listed building consent to carry out a loft conversion.

Apply for a Lawful Development Certificate to prove that a dormer window or roof light is lawful. This is both for existing and proposed items.

To find out whether your proposal is likely to be accepted, you can apply for pre-planning application advice.

You can apply via the national planning portal. To find out what information is needed with your application, see making a planning application.

If you need further advice about whether you need planning permission, contact planning advice and information.