How much does an extension cost?

What affects the cost

• Size and design: how much space you’re adding, the shape of the extension and whether it’s single or two-storey.
• Materials and finishes: what you choose for the outside, the glazing, the kitchen or bathroom fittings and the flooring.
• Ground conditions and foundations: what’s below ground affects the foundations you need.
• Access to the site: how easily materials and machinery can reach where the extension will go.
• Services: power, water and drainage, and what needs moving or connecting.
• Approvals: whether you need planning permission, building regulations approval or a party wall agreement, and the fees involved.

What your detailed proposal covers

Your detailed proposal sets out what’s included and anything that isn’t, such as council fees for planning or building control, or items you’re supplying yourself, so you know exactly what you’re comparing. Before work starts, we agree a clear payment schedule with you, linked to stages of the build.

Get a detailed proposal

The best way to find out what your extension will cost is to talk to us. We’ll come and see you, talk through what you’d like and put together a detailed proposal for your project. If you have a budget in mind, tell us early, as it helps us suggest options that fit.

This is general guidance for England, not legal advice. The rules can change and can differ for your property, so always check with your local council before you start.