England homeowner guide
Some house extensions in England can use permitted development rights, but the limits are detailed and planning permission is only one part of the approval process.
HomeProjects.money editorial team substantively reviewed this page on 18 August 2026 against current GOV.UK guidance. It applies to houses in England. Scotland, Wales and Northern Ireland have separate planning systems, and flats do not have the same householder permitted development rights.
Permitted development rights can be removed or restricted by an Article 4 direction, a condition on an earlier planning permission or the property's location and status. Conservation areas, National Parks, Areas of Outstanding Natural Beauty, the Broads, World Heritage Sites, listed buildings and land within their setting can require additional checks. Previous extensions may also count when measuring limits from the original house.
The original house generally means the house as it stood on 1 July 1948 or, if built later, as first built. Buying a house with an existing extension does not reset that baseline.
For a single-storey rear extension, the standard depth limit is generally 4 metres for a detached house and 3 metres for another house. The larger-home-extension process can allow up to 8 metres for a detached house and 6 metres for another house, subject to prior approval and neighbour consultation. A single-storey extension is generally limited to 4 metres high, and eaves within 2 metres of a boundary are generally limited to 3 metres.
A side extension under permitted development must generally be single storey, no more than 4 metres high and no wider than half the width of the original house. Other limits cover the proportion of land around the original house, roof form, upper-floor windows, balconies, materials and extensions forward of the principal elevation. These summaries are not a substitute for checking every condition in the official technical guidance.
If every relevant limit and condition is met and the right has not been removed, a planning application may not be required. A lawful development certificate can provide formal evidence that the proposal is lawful.
The larger-home-extension route requires an application to the local planning authority before work starts. Neighbour consultation is part of that process; absence of a full planning application does not mean no procedure applies.
Apply when the design falls outside permitted development or rights are restricted. Local plan policies, design, neighbours, heritage, trees, flood risk, ecology and highways can affect the decision.
Planning permission and building-regulations approval answer different questions. An extension will normally require building-regulations approval for structure, fire safety, insulation, ventilation, drainage, electrics and other technical matters even when planning permission is not required. Party wall duties, build-over agreements, restrictive covenants, freeholder consent and listed-building consent are also separate regimes.
Do not start work on the assumption that a contractor will arrange every approval. Put responsibility for drawings, applications, inspections and completion documents in the written scope.
This is general information, not legal or planning advice. The local planning authority decides how national and local rules apply to a particular property.
Related Planning Tools
Estimate full project costs, compare extension types, and plan contingency before submitting planning applications or requesting contractor bids.
Interactive cost estimator covering single and multi-storey builds across all UK regions with regional labour multipliers.
Detailed cost breakdown per square metre for standard, mid-range, and premium extension specifications.
Complete cost planning for single-storey rear and side extensions under permitted development rules.