Do I Need Planning Permission for a House Extension?

Do I need planning permission for a house extension? Many house extensions in England can be built without a planning application under permitted development rights, provided they meet the size and siting limits in Schedule 2, Part 1 of the Town and Country Planning (General Permitted Development) (England) Order 2015. A single-storey rear extension can extend up to four metres from the rear wall of a detached house, or three metres for a semi-detached or terraced property, without planning permission.

Under the Larger Home Extension Scheme (Prior Approval), these limits increase to eight metres for detached houses and six metres for other houses, subject to a 42-day neighbour consultation process administered by the local planning authority. Two-storey extensions require full planning permission if they extend more than three metres from the original rear wall, or if any part of the extension is within two metres of the boundary.

Extensions on properties in conservation areas, Areas of Outstanding Natural Beauty, National Parks, or World Heritage Sites lose some permitted development rights. Extensions to listed buildings always require listed building consent in addition to any planning permission. Permitted development also does not apply if a previous planning condition has removed these rights, which sometimes happens on new-build estates.

A lawful development certificate, obtained from the local planning authority for around £206 (2024 fee), confirms in writing that a completed or proposed extension is lawful under permitted development. For projects requiring a full planning application, a CGI showing the extension in its context is standard supporting documentation that helps officers assess the visual impact quickly.

For loft conversions combined with extensions, the rules differ between the two elements: loft conversion permitted development has its own volume limits under Class B of Part 1, so each element must be assessed separately against the relevant class.