Northampton side extensions, designed and built
If you live in Northampton and want more space without moving, a side extension is one of the most practical ways to get it. We handle the drawings, approvals and the build.
- Guide price in NorthamptonFrom £20,500 inc VAT
- PlanningSingle storey can be permitted development
- Build time10–18 weeks on site
- Postcode districtsNN1, NN2, NN3, NN4, NN5
What is included
- Structure, roof tied into the house
- Foundations near boundaries and any drains
- New openings through the side wall
- Planning route checked or application made
Side extension prices in Northampton
For Northampton we adjust our national guide rates by ×0.95, the factor we use for East Midlands. Figures include VAT; your written quote after the survey replaces them.
Typical rates in Northampton: £1,660 to £3,230 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 2.5 m × 5 m 12 m² | £20,500 – £25,500 | £23,000 – £30,500 | £29,500 – £39,000 |
| 3 m × 6 m 18 m² | £29,500 – £36,000 | £35,000 – £45,500 | £44,000 – £58,500 |
| 3 m × 8 m 24 m² | £39,500 – £48,000 | £46,500 – £60,500 | £59,000 – £78,000 |
For a figure based on your own dimensions, use our guide-price tool.
Covering Northampton
Site visits are available across Northampton (NN1, NN2, NN3, NN4, NN5, NN7). We also work in nearby Wellingborough (9 miles), Towcester (10 miles), Daventry (12 miles), Rushden (12 miles).
For homes towards Buckinghamshire, Milton Keynes is around 15 miles away. Homes across the East Midlands often have usable side land or a driveway beside the house, which opens up side and wraparound options.
Planning and approvals in Northampton
In England a single-storey side extension can be permitted development if it is no more than 4 m high and no wider than half the width of the original house. Two-storey side extensions, and any side extension on designated land such as a conservation area, need a householder planning application.
The planning position for a specific Northampton address depends on its history and any designations, which is why we check it at the first visit.
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.
Applications are decided by the local planning authority (your district, borough or unitary council).
What happens next
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Side extension questions answered
Who do I contract with for a side extension in Northampton?
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.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Northampton, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
How long does a side extension take to build in Northampton?
On site, typically 10 to 18 weeks once approvals are in place. Before that, allow 6–14 weeks design and approvals.
How much does a side extension cost?
Our guide range is about £1,660 to £3,230 per m² including VAT, depending on specification, so a standard 18 m² single-storey side extension lands around £35,000 to £45,500 in Northampton.
Can I build a side extension without planning permission?
In England a single-storey side extension can be permitted development if it is no more than 4 m high and no wider than half the width of the original house. Two-storey side extensions, and any side extension on designated land such as a conservation area, need a planning application.
Book a free site visit in Northampton
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.