Double-storey extensions in Northamptonshire

Covering Northamptonshire

Our coverage across Northamptonshire includes Northampton, Corby, Kettering and Wellingborough.

Homes in the East Midlands

Housing in the East Midlands includes Victorian terraces, inter-war semis and newer estates, with stone-built villages in some areas where conservation controls apply.

What is a double-storey extension?

A double-storey extension adds new rooms on both the ground and first floor in one build, typically a larger kitchen or living space downstairs and an extra bedroom or bathroom above. Because the roof and foundations are shared, the cost per square metre is usually lower than a single-storey extension.

Foundations, steelwork, brick and block walls, roof
Windows, insulation, plastering, electrics and plumbing
Joining the new first floor to the existing landing

What will a double-storey extension cost?

Use these ranges to budget for double-storey extensions; the survey turns them into a fixed price for the agreed specification.

Double-storey extensions	Guide price incl. VAT
Standard specification	£2,400 to £2,900 per m²
Good specification	£2,900 to £3,400 per m²
High specification	£3,400 to £3,850 per m²

What approvals does a double-storey extension need in England?

English projects need planning clearance from the local council, building regulations sign-off from building control, and party wall notices where the work is on or near a shared boundary. We prepare and manage all three.

Two-storey rear extensions can sometimes be permitted development in England (no more than 3 m deep, at least 7 m from the rear boundary, roof pitch to match), but most two-storey and all two-storey side extensions need householder planning permission. Expect around eight weeks for a decision once the application is validated.

What can change the price or programme?

Side extensions close to a boundary are often set back or stepped down so they do not create a terraced effect.
The new roof is tied into the old one, so roof tiles and ridge details need to match.

From first call to completion

Start with a conversation. A short call or the online form is enough for us to understand what you want to build.
Survey at your house. We look at the existing structure, services and access, and agree what the design needs to achieve.
Drawings, approvals, written quote. We prepare the design, apply for the approvals it needs, and give you a fixed price in writing.
We build it. Work follows an agreed programme, with inspections at each stage and a final sign-off.

Your questions answered

How much does a two-storey extension cost?

Typically about £2,400 to £3,850 per square metre of new floor area including VAT. A 40 m² extension across two floors is often around £100,000 to £150,000 depending on specification.

How long does a two-storey extension take?

Around 14 to 24 weeks on site, plus the planning period before that.

Who deals with the council for a project in Northamptonshire?

We do. We prepare the drawings, submit planning or permitted development paperwork if needed, and arrange building control inspections.

Double-storey extensions near Northamptonshire

Learn more about double-storey extensions, or see every project we cover in Northamptonshire.