What is a single-storey extension?
A single-storey extension is a ground-floor addition, usually at the rear of a house, that enlarges a kitchen, living or dining space. Most are built with cavity walls on concrete foundations and finished with a flat roof and roof lantern or a pitched tiled roof.
How much does a single-storey extension cost in Swansea?
In Swansea, a single-storey extension typically costs £1,800–£2,650 per m² of floor area, including VAT at 20% (standard rate). For a typical 20 m² project that is roughly £36,000–£53,000. Building costs in Wales run about 8% below the UK average, and the figures for Swansea are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (14 m²) | £25,000–£37,000 |
| Typical project (20 m²) | £36,000–£53,000 |
| Larger project (28 m²) | £50,500–£74,000 |
| Rate per m² | £1,800–£2,650 |
Your quote will depend mainly on:
- Floor area and the length of new wall
- Kitchen, flooring and finishes, which we can include or leave to you
- Glazing: sliding and bifold doors cost more than French doors
- How much of the existing house is opened up
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a single-storey extension in Swansea?
Here is how the rules work for a single-storey extension in Wales. In Wales a single-storey rear extension is often permitted development: up to 4 metres beyond the rear wall and up to 4 metres high, with eaves no higher than 3 metres within 2 metres of a boundary and no more than half the land around the original house covered. Wales has no larger home extension prior approval route, so deeper extensions need a planning application, as do extensions to flats, listed buildings and houses whose rights have been removed.
The Party Wall etc. Act 1996 applies in Wales, so notices must be served before work on a shared wall, on the boundary, or excavation close to a neighbour’s foundations.
We check this for your address before design work starts, so there are no surprises later.
What we handle
From survey to sign-off, the job normally involves:
- Cavity walls, insulation and roof to current building regulations
- Knock-through to the existing house with steel beams
- Doors, windows and roof glazing installed
- Building control inspections and completion certificate
- Measured survey and design drawings
- First and second fix electrics, heating and plastering
How long does it take?
Expect 10 to 14 weeks on site for a typical rear extension, after approvals. Allow time beforehand for drawings and approvals, usually 6 to 12 weeks.
Building in Swansea
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Our Swansea coverage includes postcode districts SA1, and we also work in nearby places such as Clydach, Gorseinon and Neath.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about single-storey extensions in Swansea
How much does a single-storey extension cost in Swansea?
In Swansea, a single-storey extension typically costs £1,800–£2,650 per m² of floor area, including VAT at 20% (standard rate). A typical 20 m² project comes to roughly £36,000–£53,000. Your fixed price depends on the survey and drawings.
How long does a single-storey extension take?
Once approvals are in place, a typical rear extension takes 10 to 14 weeks on site. Design and approvals usually take another 6 to 12 weeks beforehand, depending on whether a planning application is needed.
Do I need planning permission for a single-storey extension in Swansea?
In Wales a single-storey rear extension is often permitted development: up to 4 metres beyond the rear wall and up to 4 metres high, with eaves no higher than 3 metres within 2 metres of a boundary and no more than half the land around the original house covered. Wales has no larger home extension prior approval route, so deeper extensions need a planning application, as do extensions to flats, listed buildings and houses whose rights have been removed.
Can I stay in the house during the build?
Usually yes. We build the shell before opening up the back wall, so the house stays weathertight for most of the job. There will be a few weeks when the kitchen or back room is out of use.
What is a build-over agreement?
If a public sewer runs within 3 metres of the extension, the water company normally has to agree to the work before it starts. We check sewer records during design and apply where needed.
Who approves a single-storey extension in Swansea?
Planning matters in Swansea go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.