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.
Cost is usually the first question about a single-storey extension, so here is the guide for the South East: £39,000–£84,000 including VAT. We cover the whole of Oxfordshire, with Oxford, Banbury, Abingdon and Bicester among the main centres. Because each UK nation sets its own rules, we check the requirements in England for your property, then put a firm price on paper following a free survey.
- Guide price
- £39,000–£84,000 inc VAT
- Time on site
- 10–16 weeks on site
- Planning rules
- England
- Price level
- About 12% above the national guide
- Towns listed
- 6
- Survey
- Free, with a written quote
How much does a single-storey extension cost in Oxfordshire?
What should you budget for a single-storey extension in Oxfordshire? Use the figures below as a starting point. Prices in the South East sit about 12% above the national guide, so the range here is £39,000–£84,000 including VAT. Your fixed price comes in writing once we've surveyed the property, at no charge.
| Type of job | What it usually involves | Guide in Oxfordshire |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £24,500–£45,000 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £39,000–£84,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £78,000–£146,000 |
What moves the price up or down:
- Floor area, shape and number of corners
- Roof type, rooflights, lanterns and the amount of glazing
- Steelwork needed to open into the existing house
- Finishes, kitchen, flooring and heating specification
Scope of the work
- Groundworks, foundations and below-ground drainage
- Cavity walls built and insulated to building regulations
- Steel beams to open into the existing house
- Electrics and plumbing by qualified trades, with certificates
- Windows and external doors, including bifolds if chosen
- Building control inspections and completion certificate
Housing across Oxfordshire
West Oxfordshire's Cotswold villages are built of honey-coloured limestone, while Banbury and the north use orange ironstone. Oxford has Victorian terraces in Jericho and East Oxford and Gothic brick villas in North Oxford. Didcot, Bicester and Witney have grown with large new estates around older market-town centres.
Stone cottages often need lime pointing and conservation-sensitive windows. Victorian terraces suit loft conversions and side-return extensions, and newer estate homes commonly take garage conversions and garden landscaping.
Low ground around Oxford and Abingdon floods from the Thames and its tributaries; the Cotswold uplands are more exposed to wind and frost.
Do you need permission in Oxfordshire?
Oxfordshire is in England, so the planning and building rules set out below are the ones that apply. We confirm the details with the council before we quote.
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.
The four stages
Survey and measure
We arrange a free site survey on a date convenient to you. We measure up, look at the existing structure and access, and discuss your plans for a single-storey extension so the price reflects your home.
Written quote
The quote arrives in writing, not over the phone. It covers the full scope, the finishes you've chosen, any exclusions and the payment schedule, with a fixed price tied to that specification.
Booking the work
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.
The work itself
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 Oxfordshire
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.
Can you combine a single-storey extension with other work?
Yes. Because we manage several trades under one contract, we can plan a single-storey extension alongside other work on your Oxfordshire home, such as new windows with rendering, or a kitchen refit with an extension. Combining jobs can reduce repeat set-up such as scaffolding, skips and access, and every element is listed and priced in the same written quote.
Do you cover Oxford, Banbury and Abingdon?
Yes. As well as Oxfordshire, we cover Oxford, Banbury and Abingdon and the rest of Oxfordshire. Our coverage is UK-wide, so the process is the same wherever you are: a free site survey, a quote in writing that fixes the price for the agreed scope, and one point of contact while the work is planned and carried out.
How long does a single-storey extension take to build?
A single-storey extension usually takes 10–16 weeks on site, from digging foundations to final plastering. Bad weather, deep foundations or a complex roof can add time. Before work starts, allow several weeks for drawings, structural calculations and building control approval, and longer if planning permission is needed. We give you a stage-by-stage programme with your quote so you know what happens each week.
How much does a single-storey extension cost?
A typical single-storey rear extension of 15–25m² costs £39,000–£84,000, 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.
Towns in Oxfordshire
Looking for a single-storey extension somewhere in Oxfordshire? Start with the towns below; each links to a page with pricing for your region and coverage details.