A double-storey extension adds two floors of new space to your house in one build, typically a larger kitchen or living room downstairs with an extra bedroom, bathroom or en-suite above, sharing one set of foundations and one roof.
Across Oxfordshire, people look into a double-storey extension to replace something worn out, to make the house work better for them, or to get it ready for a sale. We cover Oxford, Banbury, Abingdon and Bicester and the smaller towns around them, working to the rules that apply in England. Expect a guide of £67,000–£134,000, VAT included, in the South East, and every quote follows a free visit.
- Guide price
- £67,000–£134,000 inc VAT
- Time on site
- 14–22 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 double-storey extension cost in Oxfordshire?
Budgeting for a double-storey extension in Oxfordshire? The numbers below include VAT and are adjusted for the South East, where costs are about 12% above the national guide. The headline range is £67,000–£134,000. Nothing is final until we have measured up at a free survey and agreed the specification with you.
| Type of job | What it usually involves | Guide in Oxfordshire |
|---|---|---|
| Small (15–20m² total) | A compact rear or side extension adding a small room on each floor. | £45,000–£73,000 |
| Typical (30–40m² total) | A larger kitchen or living room below with a double bedroom or en-suite above. | £67,000–£134,000 |
| Large (50m² plus total) | Wide or deep extensions, often with a new bathroom, steelwork and high-spec glazing. | £112,000–£202,000 |
The main things that change the figure:
- Combined floor area across both storeys
- How the new roof joins the existing roof
- Bathrooms, en-suites and plumbing on the upper floor
- Foundation depth, ground conditions and drains to divert
What do you get?
- Groundworks, foundations and below-ground drainage
- Insulated cavity walls with brick or render to match the house
- First-floor joists, stud walls and new openings upstairs
- Roof structure tied into the existing roof, tiled to match
- Electrics, plumbing and heating by qualified trades, with certificates
- Windows, external doors, plastering and internal doors
Homes in 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?
Because Oxfordshire falls under England's rules, the guidance below is the version relevant to you. Before sending a price, we check your property's position with the council.
In England, a two-storey rear extension can only be permitted development if it is no more than 3 m deep, at least 7 m from the rear boundary and finished to match the house. Most double-storey and all two-storey side extensions need full planning permission.
Building Regulations approval is needed, with structural calculations for beams, foundations and the roof. The Party Wall etc. Act 1996 often applies on semi-detached and terraced houses.
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
A free survey comes first. It gives us what we need to price a double-storey extension properly, including dimensions, existing materials and access for deliveries, and gives you the chance to ask anything you like.
Your fixed price
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.
Booking the work
Once you accept, we agree start dates, order materials and deal with any planning, building control or neighbour notices the job needs. You'll know who is coming and when before work begins.
On site to finish
The job proceeds in the order set out in the programme, with dust and debris kept under control. Finally we tidy away, inspect the work together and pass the finished project over to you with its paperwork.
How we work
Frequently asked questions
Do I need planning permission for a two-storey extension?
Most two-storey extensions need planning permission, but it depends on the size, height and position, your home's location, whether it is listed or in a conservation area, and which UK nation you are in. In England, a two-storey rear extension can sometimes be built under permitted development if it is no deeper than 3m and at least 7m from the rear boundary. We check what applies before quoting.
Is a double-storey extension better value than single-storey?
A double-storey extension usually gives better value per square metre than a single-storey one, because the same foundations and roof serve twice the floor area. The overall cost is higher, and planning can be harder because of the effect on neighbours. If you might want an extra bedroom later, building both floors now avoids a second round of disruption and scaffolding.
Do I need planning permission in Oxfordshire?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. Oxfordshire 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.
Can the new upstairs room have its own bathroom?
A new upstairs room can usually have an en-suite, provided waste pipes can reach the soil stack or a new one can be installed. Running the waste pipe to the right falls is the main design question, and a pumped system is an option where gravity will not work. We plan bathroom positions at the design stage so pipes, ventilation and insulation are built in rather than added later.
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.
Towns in Oxfordshire
Homes in all of the following Oxfordshire towns can get a written quote for a double-storey extension. Open a town page to see prices and the postcodes we cover.