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.
Whatever prompted you to look into a double-storey extension, whether wear and tear, a growing family or plans to move, we can survey your Swindon home and give you a price in writing. Homes in the South West typically come in at £61,000–£122,000, VAT included, for this kind of work. We also cover Cirencester, Chippenham and Melksham, and the same steps apply wherever you are in Wiltshire.
- Guide price
- £61,000–£122,000 inc VAT
- Time on site
- 14–22 weeks on site
- Postcodes
- SN1, SN2, SN3, SN5 and SN25
- Planning rules
- England
- Local area
- Wiltshire
- Survey
- Free, with a written quote
What should you budget for a double-storey extension in Swindon?
The table below shows guide prices for a double-storey extension in Swindon. They are based on rates in the South West, which run about 2% above the national guide, giving an overall range of £61,000–£122,000. All figures include VAT and are firmed up after a free site survey.
| Type of job | What it usually involves | Guide in Swindon |
|---|---|---|
| Small (15–20m² total) | A compact rear or side extension adding a small room on each floor. | £41,000–£66,000 |
| Typical (30–40m² total) | A larger kitchen or living room below with a double bedroom or en-suite above. | £61,000–£122,000 |
| Large (50m² plus total) | Wide or deep extensions, often with a new bathroom, steelwork and high-spec glazing. | £102,000–£184,000 |
The main things that change the figure:
- Combined floor area across both storeys
- Bathrooms, en-suites and plumbing on the upper floor
- Foundation depth, ground conditions and drains to divert
- Scaffolding duration, access and the level of finishes
Scope of the work
- 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
- Scaffolding for the full build, erected and inspected
- Electrics, plumbing and heating by qualified trades, with certificates
- Building control inspections and completion certificate
Local housing and a double-storey extension
Salisbury has medieval and Georgian streets, the north-west around Corsham and Bradford on Avon uses Bath stone, and chalk and flint appear on the downland. Swindon has railway-village terraces and very large post-war and modern estates, and many Wiltshire villages have thatched cottages, some with chalk cob walls.
Cob and Bath stone walls need breathable, lime-based repairs, and thatched cottages may need careful roof work. Swindon's railway terraces suit loft rooms and rear extensions, while its large estates often add garage conversions, driveways and landscaping.
If your house in Swindon fits one of these patterns, it helps us anticipate what a double-storey extension will involve, though we always confirm the details on site.
Permissions for a double-storey extension in Swindon
England, Wales, Scotland and Northern Ireland each handle planning a little differently. Swindon comes under England, covered below, and we raise any questions with the council before your quote is finalised.
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
Survey and measure
Book a visit and we'll come to you. The survey covers measurements, the state of what's there now and any obvious constraints, so the price that follows is based on your actual home, not an average.
Quote in writing
You get the price in writing, itemised so you can see where the money goes. As long as the specification stays the same, that is the price you pay for a double-storey extension.
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.
Build and hand over
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.
Why homeowners choose us
Questions about a double-storey extension in Swindon
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.
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.
Who do I deal with during the job?
One point of contact manages your project from survey to handover. They schedule the trades working under our contract, keep you updated on progress, and are the person to call with any question. You don't need to coordinate builders, electricians or decorators separately, because that is part of what we do.
How is the new roof joined to the existing house?
The new roof is usually tied into the existing roof so the two read as one. On a rear extension this often means a lower ridge or a hipped end, with valleys where the slopes meet. We strip back some existing tiles, fix new rafters and battens, and lay matching tiles or slates. Lead or proprietary flashings seal the junctions so water runs off properly.
Do I need planning permission in Swindon?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. Swindon 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.
Also covering areas around Swindon
Homes across SN1, SN2, SN3 and SN5 in Swindon are within our coverage, as are those in Cirencester, Chippenham and Melksham. If you are just outside these areas, ask anyway, because we work right across the UK.