Two-storey extensions in Northamptonshire
Two-storey extensions in Northamptonshire: guide prices for the East Midlands, the rules that apply in England, and the towns we cover.
Northamptonshire at a glance
- Nation
- England
- Price region
- East Midlands
- Postcode areas
- LE, NN
- Main town
- Northampton
- Towns listed
- 9
- Site visits
- Free, no obligation
Choose your town
Guide prices in the East Midlands
| Extension type | Per m² | Typical project |
|---|---|---|
| Two-storey rear extension | £1,960–£2,650 per m² | £55,000–£74,000 |
| Two-storey side extension | £2,010–£2,700 per m² | £84,500–£113,000 |
| Two-storey wraparound extension | £2,110–£2,890 per m² | £118,000–£162,000 |
| Part single, part two-storey | £1,960–£2,700 per m² | £70,500–£97,000 |
| Extension over a garage | £1,720–£2,500 per m² | £31,000–£45,000 |
| First-floor extension over an existing single storey | £1,760–£2,550 per m² | £24,500–£35,500 |
| Two-storey front extension | £2,160–£2,940 per m² | £26,000–£35,500 |
Including VAT, Standard spec. See all prices and fees.
The main places we list in Northamptonshire are Northampton (NN1), Corby (NN17), Kettering (NN14), Wellingborough (NN8), Rushden (NN9), Daventry (NN11), Market Harborough (LE16) and Brackley (NN13). We cover the villages in between too.
Which type suits your house?
Start with what you need the space for. Bedrooms and an en-suite upstairs with a bigger kitchen below is the classic two-storey brief, but in Northamptonshire we also design annexes, home offices and bedrooms over garages.
The rules in England
Northamptonshire is in England. Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission. Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
The full England rules explained
Extension types
- Two-storey rear extensions
- Two-storey side extensions
- Two-storey wraparound extensions
- Part single, part two-storey extensions
- Extensions over a garage
- First-floor extensions
- Two-storey front extensions
By house type
- Two-storey extensions for semi-detached houses
- Two-storey extensions for detached houses
- Two-storey extensions for end-of-terrace houses
Rooms and uses
- Kitchen extensions with bedrooms above
- Extra bedroom and en-suite extensions
- Two-storey annexe extensions
- Garage conversions with a room above
Design and approvals
- Two-storey extension plans and drawings
- Planning permission for two-storey extensions
- Structural engineering for two-storey extensions
- Building regulations for two-storey extensions
- Party wall notices for extensions
- Design and build two-storey extensions
Questions about extensions in Northamptonshire
How much does a two-storey extension cost in Northamptonshire?
In the East Midlands our guide for a two-storey rear extension is £1,960–£2,650 per m² including VAT, about £55,000–£74,000 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Side and wraparound extensions cost a little more per m².
Do I need planning permission in Northamptonshire?
Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission. Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026).
Do you cover the whole of Northamptonshire?
Yes. We list the main towns here, but we cover the whole of Northamptonshire including villages. The first site visit is free.
What happens at the first visit?
We look at your house, the boundaries, access and drains, talk through what you need and explain the approvals. Then we price the design stage, including the measured survey, in writing.