Single or double storey extension to the rear of a property. Covers full structural build from foundations to weathertight shell including all masonry, roof, and external joinery.
Typical cost
£20,000 — £34,000
Typical duration
8-12 weeks
Certificate
Building Regulations approval required
Scope type
flexible
Typical tasks
Mark out and excavate foundations
Build inner and outer leaf brickwork/blockwork
Construct flat or pitched roof to design
Install bifold, sliding, or standard door
Install roof lights or lantern if specified
Extras & additional works
Based on a standard 20m² rear extension, costs may increase if high-end materials or complex designs are specified.
Common questions Stainesai
The price is affected by the size of the extension, choice of materials, complexity of design, and location within the UK.
Planning permission is often not required for a single-storey rear extension that falls within permitted development rights. In England, this is typically up to 4 metres beyond the rear wall for a detached house and up to 3 metres for a semi-detached or terraced house. Larger extensions may still be possible under the prior approval process. Building Regulations approval is generally required for extension work. Always confirm requirements with your local authority before work begins.
Yes, Building Regulations apply to ensure the extension meets safety and energy efficiency standards.
A standard rear extension typically takes 8-12 weeks to complete, including all construction phases.
Discuss the project scope, timeline, costs, materials, and any necessary permissions, including Building Regulations approval. Always confirm with your general builder before work begins.
Ready to post a rear extension job?
Describe what you need. Stainesai structures it into a proper scope. Your first job post is free.