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.
Looking for a single-storey extension in Devon? We organise the whole job, bringing in the trades it needs under one agreement, and you have a single contact. We cover Plymouth, Exeter, Paignton and Torquay, along with villages and suburbs nearby. The rules in England decide what consents are needed, and our guide range of £35,500–£76,000 including VAT gives you a realistic starting point for a budget.
- 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
- 11
- Survey
- Free, with a written quote
How much does a single-storey extension cost in Devon?
Below is a breakdown of typical costs for a single-storey extension in Devon. Because rates in the South West are about 2% above the national guide, the overall guide comes to £35,500–£76,000, including VAT. Size, materials and access move the figure, and a free-of-charge survey settles it.
| Type of job | What it usually involves | Guide in Devon |
|---|---|---|
| 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 |
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’s included?
- 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
- Steel beams to open into the existing house
- Electrics and plumbing by qualified trades, with certificates
- Plastering, screed floor and internal doors
Housing across Devon
Devon is known for cob and thatch cottages, especially in mid and east Devon, alongside granite on Dartmoor and red sandstone around Exeter. Exeter and Plymouth have Georgian and Victorian terraces, Plymouth's centre was largely rebuilt after the war, and seaside towns such as Torquay and Exmouth have rendered villas and newer estates.
Cob and stone homes need breathable lime plaster and render rather than cement. Victorian terraces suit loft rooms and window replacement, while post-war and newer homes often take extensions, rendering and roofline renewal.
Mild but wet, with strong coastal winds; exposed elevations need render and pointing specified for driving rain, and cob walls must be kept dry at the base.
Do you need permission in Devon?
The notes below cover England, which is where Devon sits. Rules change and every property is different, so we speak to the council before pricing your job.
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
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.
Booking the work
We handle the paperwork side: checking whether planning permission or building control approval is needed, submitting applications where they are, and scheduling the trades and materials around your dates.
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.
How we work
Frequently asked questions
Which postcodes in Devon do you cover?
We cover PL1, EX1, TQ3 and TQ1, along with the rest of Devon. If your postcode is not listed, get in touch anyway: our coverage is UK-wide, and we can usually arrange a survey wherever you live. Enter your postcode in the guide-price tool or contact form and we will confirm.
What does a typical extension build look like week by week?
A typical single-storey extension follows the same order: clearing the site and digging foundations, building walls up to roof level, then fitting the roof and windows to make it weathertight. Electrics, plumbing, insulation and plastering follow. The last stage is opening into the house, laying the screed and fitting doors and finishes. Building control inspects at key stages, and we book those visits for you.
Can I stay at home during the work?
In most cases, yes. Most people can live at home throughout, and we plan the work to keep disruption down by protecting floors, agreeing working hours and keeping access routes clear. Bigger jobs affecting kitchens, bathrooms or heating may mean a short spell with reduced facilities, and we talk this through with you at the survey.
Do I need an architect for an extension?
You need proper drawings for an extension, but not always a full architect service. A designer or architectural technician can produce planning and building regulations drawings, and a structural engineer provides beam and foundation calculations. If you already have drawings, we price from them. If not, we can arrange the drawings and calculations as part of the project so everything is coordinated from the start.
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.
Towns in Devon
Choose your town from the list to see how we price and plan a single-storey extension in your part of Devon, including typical time on site.