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.
We arrange a double-storey extension for homeowners in Falmouth and the wider Cornwall. The job is planned, priced and managed by us and carried out by tradespeople engaged under our contract, so there is one agreement and one contact. On a typical home the work takes 14–22 weeks on site, and guide pricing in the South West is £61,000–£122,000, VAT included.
- Guide price
- £61,000–£122,000 inc VAT
- Time on site
- 14–22 weeks on site
- Postcodes
- TR11
- Planning rules
- England
- Local area
- Cornwall
- Survey
- Free, with a written quote
How much does a double-storey extension cost in Falmouth?
Use the table to gauge the cost of a double-storey extension in Falmouth before we visit. Figures include VAT and are scaled for the South West, coming out about 2% above the national guide, which gives £61,000–£122,000 overall. After a free survey, you receive a fixed written price.
| Type of job | What it usually involves | Guide in Falmouth |
|---|---|---|
| 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 |
Your price depends mostly on:
- 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’s included?
- 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
- Scaffolding for the full build, erected and inspected
- Windows, external doors, plastering and internal doors
Homes in Cornwall
Older Cornish homes are often built of granite or slatey local stone, with slate roofs and sometimes slate-hung walls facing the weather. Cob cottages survive in places, Truro and Falmouth keep Georgian and Victorian streets, and many towns have rendered post-war houses, bungalows and newer estates on their edges.
Cornwall faces Atlantic gales, driving rain and salt-laden air, so render, pointing and window hardware on exposed elevations need a suitably robust specification.
That mix of housing shapes how we approach a double-storey extension in Falmouth: the age and construction of your home affect the materials, the method and, in the end, the price.
Do you need permission in Falmouth?
The notes below cover England, which is where Falmouth sits. Rules change and every property is different, so we speak to the council before pricing your job.
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
Free site survey
First, someone visits your home in Falmouth to see the space, take measurements and note anything that could affect the work, such as access or the condition of what is there. There is no charge for this visit.
Written quote
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.
Booking the work
With the quote agreed, we book the work in and handle preparation: permissions where needed, building control notifications, material orders and access arrangements for your Falmouth property.
Build and hand over
Our trades complete a double-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.
Why homeowners choose us
Double-storey extensions in Falmouth: questions
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 Truro, Redruth and Camborne?
Yes. As well as Falmouth, we cover Truro, Redruth and Camborne and the rest of Cornwall. 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.
Do I need planning permission in Falmouth?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. Falmouth 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.
Will the extension affect my neighbours?
A double-storey extension can affect neighbours' light, outlook and privacy, which is why planning departments look closely at height, depth and window positions. Side windows facing neighbours often need obscure glass. Work near a shared wall may also need party wall notices; the Party Wall etc. Act 1996 applies in England and Wales only. We talk through these points early so the design is realistic.
How much does a double-storey extension cost?
A typical double-storey extension of 30–40m² across both floors costs £61,000–£122,000, built to a plastered finish. As a rough guide, allow around £1,400–£2,600 per square metre plus fixed costs for groundworks, scaffolding and fees. The second storey usually costs less per square metre than the first, because foundations and roof are shared. Bathrooms upstairs and a complex roof add most. We confirm a fixed price after the survey.
Near Falmouth
Addresses in TR11 are all covered for Falmouth, along with Truro, Redruth and Camborne close by. Give us your postcode when you get in touch and we will confirm the details.