Northamptonshire house extensions
More space without moving: we plan and build extensions across Northamptonshire, with one team for the drawings, the council and the build.
- Towns listed9
- Price regionEast Midlands (×0.95)
- Planning rulesEngland
- Postcode districts23
Towns we cover in Northamptonshire
Towns we cover here include Northampton, Corby, Kettering, Wellingborough.
Do extensions in Northamptonshire need planning permission?
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.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
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.
Guide prices for Northamptonshire
Prices on this page use our East Midlands factor of ×0.95, include VAT at 20% and cover the build; your written price follows a survey and agreed drawings.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Side return extensions | 11 m² | £25,000 – £31,500 |
| Single-storey rear extensions | 20 m² | £38,500 – £49,500 |
| Kitchen extensions | 20 m² | £39,500 – £50,500 |
| Double-storey extensions | 32 m² | £54,500 – £71,500 |
| Wraparound extensions | 25 m² | £54,500 – £69,000 |
| Conservatory replacement extensions | 14 m² | £28,500 – £37,000 |
What works best for Northamptonshire houses?
Homes across the East Midlands often have usable side land or a driveway beside the house, which opens up side and wraparound options.
The types we would usually look at first for a home in Northamptonshire are side extensions, conservatory replacement extensions and double-storey extensions, depending on the garden and how the house is laid out.
Extension types and starting prices
- Orangery extensions · from £28,500
- Side extensions · from £20,500
- Utility and boot room extensions · from £13,000
- Pitched roof extensions · from £21,000
- Timber frame extensions · from £19,500
- Single-storey rear extensions · from £19,500
- Porch extensions · from £3,800
- Wraparound extensions · from £34,000
- Side return extensions · from £17,000
- Planning permission for extensions · from £300
- Annexe extensions · from £52,000
- Extensions over a garage · from £22,500
- Flat roof extensions · from £19,500
- Home office extensions · from £15,000
- Bungalow extensions · from £24,500
- Extension plans and drawings · from £1,100
- Bedroom extensions · from £24,500
- Kitchen extensions · from £25,500
- Conservatory replacement extensions · from £19,000
- Building regulations for extensions · from £850
- Double-storey extensions · from £36,000
- Glass box extensions · from £28,500
Neighbouring areas
Questions about extensions in Northamptonshire
How much does an extension cost in Northamptonshire?
With our East Midlands factor (×0.95), a standard-spec 20 m² single-storey extension is a guide £38,500 to £49,500 including VAT. Prices for every type are linked on this page.
How long does an extension take in Northamptonshire?
Usually 2 to 4 months of design and approvals, then 10 to 16 weeks on site for a single-storey extension or 16 to 24 weeks for two storeys.
Who do I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Will my neighbours need to be told?
If you apply for planning or prior approval the council notifies them, and in England party wall notices may be needed for work near a shared boundary.
Book a free site visit in Northamptonshire
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.