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.
If you are planning a single-storey extension anywhere in Wiltshire, including Swindon, Salisbury, Trowbridge and Chippenham, we can visit, measure up and talk through the options. The planning and building regulations we work to are those for England, and we check them for your address before quoting. Prices remain guide figures for the South West, at £35,500–£76,000 including VAT, until the survey is done.
- Guide price
- £35,500–£76,000 inc VAT
- Time on site
- 10–16 weeks on site
- Planning rules
- England
- Price level
- About 2% above the national guide
- Towns listed
- 5
- Survey
- Free, with a written quote
How much does a single-storey extension cost in Wiltshire?
Here is how the guide price for a single-storey extension breaks down in Wiltshire. We start from national figures and adjust for the South West, which comes out about 2% above the national guide. The resulting range, VAT included, is £35,500–£76,000, and a survey, at no cost to you, firms it up.
| Type of job | What it usually involves | Guide in Wiltshire |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £22,500–£41,000 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £35,500–£76,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £71,000–£133,000 |
Your price depends mostly on:
- Floor area, shape and number of corners
- Roof type, rooflights, lanterns and the amount of glazing
- Ground conditions, foundation depth and drains to divert
- Finishes, kitchen, flooring and heating specification
What do you get?
- Groundworks, foundations and below-ground drainage
- Cavity walls built and insulated to building regulations
- Flat or pitched roof, with rooflights or a lantern if specified
- Windows and external doors, including bifolds if chosen
- Plastering, screed floor and internal doors
- Building control inspections and completion certificate
Housing across Wiltshire
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.
Salisbury Plain and the downs are exposed to wind and frost, while river valleys around Salisbury and the Avon can flood.
Planning and building rules in Wiltshire
For anyone in Wiltshire, the relevant framework is England's. The summary below is general, so we always contact the council about your address before putting a price in writing.
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
We look at the job
It starts with a survey at the property, free of charge. We check condition, access and services, ask how you want the finished result to look, and answer any questions you have about a single-storey extension.
Quote in writing
After the survey we send a quote for a single-storey extension that fixes the price for the scope we've agreed. If you want to change materials or scope, we revise it in writing before anything is booked.
Dates and permissions
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
During the work we protect the areas around it and tidy up at the end of each day. Once complete, we check the finish, remove our materials and hand over paperwork such as building control sign-off where it applies.
How we work
Questions about a single-storey extension in Wiltshire
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.
Can we stay at home during the build?
Most people stay at home while we build a single-storey extension, because the new structure goes up outside before we break through. The disruptive part is usually the last few weeks, when we open into the house and fit the kitchen. We put up dust screens, keep a safe route through the house and agree a temporary kitchen setup if needed. Water and power are only off for short, planned periods.
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.
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.
How much will a single-storey extension cost in Wiltshire?
As a guide, expect to pay £35,500–£76,000 including VAT for a single-storey extension in Wiltshire. That range is adjusted for the South West, which runs about 2% above the national guide. Where your project lands depends on size, materials, access and the condition of what is already there. We confirm a fixed price in writing after a free survey of your home.
Towns in Wiltshire
These are the towns in Wiltshire where you can book a free survey for a single-storey extension. Each has its own page with guide prices and coverage details.