In England, a single-storey rear extension, including a conservatory, can extend up to eight metres from the rear wall of a detached house or six metres for other houses under permitted development if the local planning authority is asked to decide whether its prior approval is required, and neighbours are consulted as part of that process.

The standard limit and the larger limit

The Planning Portal, which describes the planning system in England (and says policy in Wales may differ), explains that a single-storey rear extension under permitted development cannot extend beyond the rear wall of the original house by more than four metres for a detached house, or three metres for any other house. Where the property is not on Article 2(3) designated land or a Site of Special Scientific Interest, and subject to prior approval, that limit is increased to eight metres for a detached house or six metres for any other house. Single-storey rear extensions also cannot exceed four metres in height.

The Planning Portal says these permitted development rules summarise Schedule 2, Part 1, Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015. They apply to houses, not flats and maisonettes, converted houses or houses created under certain change-of-use rights, and they do not apply where a planning condition, Article 4 Direction or other restriction removes the rights.

What counts as the original house and designated land

The “original house” is the house as first built, or as it stood on 1 July 1948 if built earlier, so earlier extensions by previous owners count towards the limits. Article 2(3) designated land includes conservation areas, areas of outstanding natural beauty, the Broads, National Parks and World Heritage Sites, and the larger 8m/6m limits are not available there.

How the application works

A householder applies to the local planning authority, providing a written description that states how far the extension projects beyond the rear wall of the original house, the height at the eaves and the highest point, a site plan showing the proposal and any existing enlargement it joins, the addresses of adjoining properties including those to the side, front and rear even if not physically attached, and contact details. The Planning Portal guidance note (version 2024.1 for England) says a plan drawn to scale helps, and that if information is insufficient the authority can ask for more or refuse the application.

There is a fee for most prior approval applications. The guidance note says it can be waived if the proposal is solely for extensions and alterations to a disabled person’s dwelling to improve access, safety or comfort, or if a planning application for the same site is made by the same applicant on the same date and a fee is payable for it.

Neighbour consultation and the 42-day period

The authority serves a notice on adjoining owners or occupiers, describing the proposal and stating when the application was received, when the 42-day determination period ends and the date by which objections must be received, which must give neighbours at least 21 days. If any adjoining neighbour objects within that period, the authority’s prior approval is required and it must decide whether the impact on the amenity of all adjoining properties is acceptable. The development can go ahead if the authority notifies the developer in writing that prior approval is not required because no objections were received, or that it has found the effect on amenity acceptable. If the authority does not notify a decision within the 42-day period, the development may go ahead. A refusal can be appealed.

Conditions and cautions

The guidance note stresses that all other permitted development restrictions and conditions still apply, and that it is not possible to use the prior approval process retrospectively, so it must be completed before work starts. The extension must be built in accordance with the details approved or, where no objections were raised or no decision was made, the details submitted, unless the authority agrees changes in writing.

The Planning Portal also notes that an extension adding more than 100 square metres of floor space may be liable for the Community Infrastructure Levy, and that permitted development is separate from Building Regulations, which must be considered independently. Its guidance is introductory, and local rules may affect what is needed, so a householder should confirm the position with the local planning authority.

FAQs

Does a conservatory count as a single-storey rear extension?

The Planning Portal says that adding a conservatory to a house falls within the same planning rules as any other home extension, so the single-storey rear extension limits and the prior approval process apply.

What happens if a neighbour objects?

The authority must then decide whether the impact on the amenity of all adjoining properties is acceptable before the extension can proceed, according to the Planning Portal guidance note.

Does this apply in Wales, Scotland or Northern Ireland?

The Planning Portal guidance relates to England, and it says policy in Wales may differ. Scotland and Northern Ireland have their own planning rules.

Bottom line

The larger 8m and 6m rear extension limits in England depend on prior approval: apply first, allow the neighbour consultation and 42-day period, and build only to the approved or submitted details. The route is unavailable on designated land and cannot be used after building has started. This is general information, not planning advice; confirm requirements with your local planning authority.

Sources

This guide draws on the following primary sources, current as of 20 September 2026:

• Planning Portal, “Planning Permission – Extensions”
• Planning Portal, “Planning Permission – Conservatories”
• Planning Portal, “Extensions: Prior approval”
• Planning Portal, “Application to determine if prior approval is required for a proposed Larger Home Extension” (guidance note, PDF, V2024.1 England)

Related guides

Compare Conservatories is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not legal or planning advice on any specific property — always confirm requirements directly with your local planning authority.