Planning permission is not normally required. However, permission is required where you extend or alter the roof space and it exceeds specified limits and conditions.
A loft conversion for your house is considered to be permitted development, not requiring an application for planning permission, subject to the following limits and conditions:
- If you live in a terraced house your extension must be less than 40 cubic metres or in any other case less than 50 cubic metres.
- You may not build a loft extension beyond the plane of the existing roof slope on the principal elevation of the dwellinghouse.
- The roof extension cannot be higher than the highest part of the existing roof.
- Other than for hip to gable enlargements, any roof extension must be at least 20cm from the eaves of the existing roof.
- The materials used in your roof extension must match, as much as possible, the appearance of the existing dwellinghouse. UPVC will not be acceptable, other than possibly for windows. Loft extensions are expected to be finished in hanging tiles, render or brickwork to match your house.
- Windows within 10.5 metres of a boundary on the side elevation of a roof slope will need to be obscure-glazed or non-opening, to protect the privacy of your neighbours.
- A Juliet balcony with no platform, which does not project from the roof extension by more than 300mm, and is not within 10.5 metres of any boundary opposite the side elevation of the house, would be permitted. Any other form of balcony, roof terrace or veranda will require planning permission.
- Hip to gable extensions are permitted.
- Roof extensions are not permitted in conservation areas, national parks, areas of outstanding natural beauty or World Heritage Sites, and you must seek planning permission to build them.
- If the building is listed you should consult with your local planning authority.
Removal of permitted development rights
You need to be aware of whether the permitted development rights have been removed from your property by the Local Planning Authority. If they have been removed, you must submit a planning application for the work.
The Local Planning Authority may have removed some of your permitted development rights as a condition of the original planning permission for your property. This information will be available on the planning register held by the Local Planning Authority. Permitted development rights may also have been removed by an 'Article 4' direction. These are most common in conservation areas where the character of an area could be threatened by unmanaged development. Your solicitor should have informed you of whether an article 4 direction exists when you purchased your property, but you can check with the Local Planning Authority if you are not sure.
The Welsh Government has produced a technical guide, and a householder guide, available here, to help you understand how permitted development rules might apply to your circumstances.