Single-storey rear extensions

A single-storey rear extension adds a new ground-floor room on the back of your house, usually to create a bigger kitchen, a kitchen-diner or a family room that opens onto the garden. It is the most common type of house extension in the UK because it adds useful space without touching the bedrooms or the roofline at the front.

We design and build the whole thing: the survey, drawings, planning route, foundations, structure, roof, glazing and finishes, through to the final building control sign-off. Most single-storey rear extensions fall between 3 m and 6 m deep, and many can be built under permitted development without a full planning application.

What is included

• Measured survey and design
• Planning route checked and the right approval obtained
• Building regulations drawings and structural calculations
• Foundations, drainage and groundworks
• Walls, steel beams and the new opening into the house
• Flat or pitched roof, rooflights or lantern
• Doors, windows, insulation, plastering and first fix to finish

Who it suits

• Semi-detached and detached houses with a usable rear garden
• Terraced houses that want a deeper kitchen across the full width
• Homeowners who want open-plan living onto the garden

Design advice

Depth is the big decision. Every extra metre adds floor area but also takes garden and can push you out of permitted development. We draw the room at two or three depths so you can see the trade-off in space, light and cost before anything is fixed.

How much does it cost?

National guide prices including VAT at 20%. Build cost only; design, structural and council fees are extra. Your area page shows prices adjusted for your region.

Planning rules across the UK

England

In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.

Wales

In Wales a single-storey rear extension can usually project up to 4 m beyond the rear wall without a planning application, if it is no more than 4 m high, keeps eaves to 3 m and overall height to 4 m within 2 m of a boundary, and covers no more than half the land around the original house. Wales has no larger home extension prior approval scheme.

Scotland

In Scotland, householder permitted development rules (Class 1A for single-storey ground-floor extensions and Class 1B for extensions of more than one storey) allow some smaller extensions without a planning application, within limits on depth, height and distance from the boundary. Conservation areas and listed buildings are more restricted. Separately, almost every extension needs a building warrant from the council before work starts.

Northern Ireland

In Northern Ireland the Planning (General Permitted Development) Order 2015 lets some single-storey rear extensions go ahead without planning permission, up to 3 m on a semi-detached or terraced house and 4 m on a detached house, within height and boundary limits. Larger, side and two-storey extensions normally need planning permission from the council, and building control approval is separate.

Building regulations and neighbours

Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.

In England and Wales, if the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations. Scotland and Northern Ireland have no Party Wall Act.

Questions about single-storey rear extensions