A single-storey extension is a new ground-floor room built onto your house, usually at the rear or side, with its own foundations, walls and roof, creating a bigger kitchen, living space or bedroom without moving home.
In Northamptonshire, we price a single-storey extension against our guide for the East Midlands, £33,500–£72,000 including VAT, then adjust it once we have surveyed your home. We work across Northampton, Corby, Kettering and Wellingborough and the rest of the county or region. Planning and building control requirements follow the rules for England, and we look into your property's position before a written quote is sent.
- Guide price
- £33,500–£72,000 inc VAT
- Time on site
- 10–16 weeks on site
- Planning rules
- England
- Price level
- About 4% below the national guide
- Towns listed
- 7
- Survey
- Free, with a written quote
Single-storey extensions prices in Northamptonshire
Every figure below is a guide for a single-storey extension in Northamptonshire, inclusive of VAT. Regional pricing for the East Midlands works out about 4% below the national guide, and the overall span is £33,500–£72,000. The survey costs you nothing, and after it we commit to a firm price for your specification in writing.
| Type of job | What it usually involves | Guide in Northamptonshire |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £21,000–£38,500 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £33,500–£72,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £67,000–£125,000 |
What moves the price up or down:
- Roof type, rooflights, lanterns and the amount of glazing
- Ground conditions, foundation depth and drains to divert
- Steelwork needed to open into the existing house
- Finishes, kitchen, flooring and heating specification
What do you get?
- Groundworks, foundations and below-ground drainage
- Flat or pitched roof, with rooflights or a lantern if specified
- Steel beams to open into the existing house
- Electrics and plumbing by qualified trades, with certificates
- Windows and external doors, including bifolds if chosen
- Plastering, screed floor and internal doors
Housing across Northamptonshire
Orange-brown ironstone is the signature material of many Northamptonshire villages, with limestone and Collyweston stone-slate roofs in the north-east. Northampton has Victorian terraces from its shoemaking era, Corby expanded as a post-war steel town, and Wellingborough, Kettering and Daventry have interwar, post-war and recent estates.
Ironstone cottages often need lime repairs and careful repointing. Terraces suit loft conversions and kitchen extensions, while estate homes commonly take garage conversions, porches and driveways.
An inland county with cold winters and clay soils that can shrink in dry spells; ironstone weathers and needs a suitable mortar.
Planning and building rules in Northamptonshire
England, Wales, Scotland and Northern Ireland each handle planning a little differently. Northamptonshire comes under England, covered below, and we raise any questions with the council before your quote is finalised.
In England, many single-storey rear extensions are permitted development: typically up to 3 m deep on a semi-detached or terraced house and 4 m on a detached house, no more than 4 m high, and covering no more than half the land around the original house. Larger rear extensions can go through the prior approval process. Side extensions, flats, listed buildings, conservation areas and homes where permitted development rights have been removed need planning permission.
Building Regulations approval is needed for almost every extension, covering foundations, structure, insulation, drainage, ventilation and fire safety. If the work is on or near a shared wall or boundary, the Party Wall etc. Act 1996 may apply.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
From survey to handover
A visit to your home
We begin by looking at the job in person. During the free survey we discuss options, materials and budget for a single-storey extension, and photograph or measure anything the quote needs to reflect.
Quote in writing
We turn the survey notes into a written quote. The price is fixed for the specification we agree, and the document sets out materials, scope and payment stages in plain language.
Getting ready
Next comes planning the work itself. We set a start date that suits you, line up the right trades, and make sure any approvals for a single-storey extension are in place before the first day on site.
Build and hand over
Our trades complete a single-storey extension while your point of contact keeps you updated. When everything is finished, we clear the site, take away waste and go through the result with you before handover.
How we work
Questions about a single-storey extension in Northamptonshire
Do I need an architect for an extension?
You need proper drawings for an extension, but not always a full architect service. A designer or architectural technician can produce planning and building regulations drawings, and a structural engineer provides beam and foundation calculations. If you already have drawings, we price from them. If not, we can arrange the drawings and calculations as part of the project so everything is coordinated from the start.
How much does a single-storey extension cost?
A typical single-storey rear extension of 15–25m² costs £33,500–£72,000, built to a plastered finish ready for your kitchen and decoration. As a guide, allow roughly £1,600–£2,800 per square metre plus fixed costs for groundworks, steelwork and fees. Smaller extensions cost more per square metre. The kitchen, flooring and large glazed doors are usually the biggest extras. We confirm a fixed price for the agreed specification after the survey.
Which postcodes in Northamptonshire do you cover?
We cover NN1, NN17, NN15 and NN8, along with the rest of Northamptonshire. If your postcode is not listed, get in touch anyway: our coverage is UK-wide, and we can usually arrange a survey wherever you live. Enter your postcode in the guide-price tool or contact form and we will confirm.
Do I need planning permission in Northamptonshire?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. Northamptonshire is in England, so England's rules apply. Many smaller jobs need no planning application, but some still need building control approval. We check what applies to your address before quoting.
What is the Party Wall Act and does it apply to me?
The Party Wall etc. Act 1996 applies in England and Wales only. In England and Wales, it requires you to give notice to neighbours before certain work on or near a shared wall, such as digging foundations within 3m of their building and deeper than its footings. Neighbours can agree or appoint a surveyor. Scotland and Northern Ireland have no equivalent Act, though general rights still apply. We identify whether notices are needed during the survey.
Towns in Northamptonshire
Our coverage for a single-storey extension in Northamptonshire includes the towns listed here. Each page explains guide costs, typical timings and the neighbouring places we also serve.