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.
From Blyth, Cramlington, Ashington and Bedlington to the quieter corners of Northumberland, homeowners can book a free survey for a single-storey extension. We look at the building, agree the scope, then send a quote in writing that fixes the cost of that scope. Work follows the rules for England, and our published range for the North East, £31,500–£68,000 with VAT, gives you a sense of budget before we visit.
- Guide price
- £31,500–£68,000 inc VAT
- Time on site
- 10–16 weeks on site
- Planning rules
- England
- Price level
- About 10% below the national guide
- Towns listed
- 4
- Survey
- Free, with a written quote
How much does a single-storey extension cost in Northumberland?
Use the table to gauge the cost of a single-storey extension in Northumberland before we visit. Figures include VAT and are scaled for the North East, coming out about 10% below the national guide, which gives £31,500–£68,000 overall. After a free survey, you receive a fixed written price.
| Type of job | What it usually involves | Guide in Northumberland |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £20,000–£36,000 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £31,500–£68,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £63,000–£117,000 |
The main things that change the figure:
- 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?
- 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
- Building control inspections and completion certificate
Housing across Northumberland
Stone dominates rural Northumberland, from sandstone farmhouses and villages to fortified bastle houses in the uplands. Alnwick, Hexham and Morpeth have historic stone centres, Berwick has Georgian streets, and south-east towns such as Ashington, Blyth and Bedlington have colliery terraces. Cramlington grew from the 1960s with planned estates.
Stone homes often need lime pointing, roof slating and breathable render. Colliery terraces suit loft conversions and rear extensions, and estate homes commonly take garage conversions and window upgrades.
The coast is exposed to cold North Sea winds, and the Cheviots and higher moorland see snow and hard frosts in winter.
Do you need permission in Northumberland?
Each UK nation sets its own consent rules, and Northumberland is in England. What follows is a plain summary; we check the specifics for your property with the council before pricing anything.
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.
How does the job run?
Free site survey
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 put everything into a written, fixed-price quote: the specification, what's excluded, staged payments and the expected time on site. Take whatever time you need to decide; there's no pressure to commit.
Getting ready
Before anyone starts, we confirm the programme in writing, check whether consents are required and arrange deliveries. If a skip or scaffolding on the road needs a permit, we apply for it.
On site to finish
The work is carried out to the agreed specification, with floors and furniture protected and the site kept tidy. At the end we clean up, walk through the finished job with you and hand over any certificates.
What you can expect from us
Questions about a single-storey extension in Northumberland
How much does a single-storey extension cost?
A typical single-storey rear extension of 15–25m² costs £31,500–£68,000, 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.
Is a flat roof or a pitched roof better on an extension?
A flat roof is quicker to build and usually costs less, gives a clean modern look and works well with a roof lantern. A pitched roof matches the main house, sheds water faster and allows a vaulted ceiling, but it costs more and its height can affect neighbours. Modern flat roofs in EPDM rubber or GRP last well when properly detailed. Planning rules on height can also decide the choice.
What happens at the survey?
We visit your home at a time that suits you, look at the area involved, take measurements and check access, condition and any services that might be affected. We talk through what you want from a single-storey extension, explain the options and answer questions. There is no charge and no obligation; afterwards we send a written quote.
Do I need planning permission for a single-storey extension?
Whether you need planning permission depends on the extension's size and height, how close it is to boundaries, your home's location, whether it is listed or in a conservation area, and which UK nation you live in. In England, many rear extensions up to 3m deep on a semi or terrace, or 4m on a detached house, can be built under permitted development. We check the rules that apply to your home before quoting.
How long will a single-storey extension take?
On a typical home, allow 10–16 weeks on site. Larger projects, older buildings and extra work found once things are opened up can extend that, while simpler jobs may be shorter. Your quote includes an estimate of time on site, and your point of contact keeps you updated on the programme as the work progresses.
Towns in Northumberland
Homes in all of the following Northumberland towns can get a written quote for a single-storey extension. Open a town page to see prices and the postcodes we cover.