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.
Getting a double-storey extension right in Gorseinon starts with understanding the house you already have: its age, how it was built and what has been altered over the years. We survey first, then commit on paper to a price that holds as long as the scope stays the same. Across Wales, guide prices run at £55,000–£110,000 including VAT, and homes in Llanelli, Swansea and Clydach are covered too.
- Guide price
- £55,000–£110,000 inc VAT
- Time on site
- 14–22 weeks on site
- Postcodes
- SA4
- Planning rules
- Wales
- Local area
- Swansea
- Survey
- Free, with a written quote
How much does a double-storey extension cost in Gorseinon?
Use the table to gauge the cost of a double-storey extension in Gorseinon before we visit. Figures include VAT and are scaled for Wales, coming out about 8% below the national guide, which gives £55,000–£110,000 overall. After a free survey, you receive a fixed written price.
| Type of job | What it usually involves | Guide in Gorseinon |
|---|---|---|
| Small (15–20m² total) | A compact rear or side extension adding a small room on each floor. | £37,000–£60,000 |
| Typical (30–40m² total) | A larger kitchen or living room below with a double bedroom or en-suite above. | £55,000–£110,000 |
| Large (50m² plus total) | Wide or deep extensions, often with a new bathroom, steelwork and high-spec glazing. | £92,000–£166,000 |
The main things that change the figure:
- Combined floor area across both storeys
- How the new roof joins the existing roof
- Foundation depth, ground conditions and drains to divert
- Scaffolding duration, access and the level of finishes
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
- Scaffolding for the full build, erected and inspected
- Electrics, plumbing and heating by qualified trades, with certificates
- Windows, external doors, plastering and internal doors
Local housing and a double-storey extension
Swansea's Victorian terraces climb its hillsides, its centre was largely rebuilt after wartime bombing, and Neath and Port Talbot have industrial terraces and post-war estates. Gower villages have stone cottages, and Pennant sandstone is common in older walls. Newer estates have grown on the edges of the main towns.
Hillside terraces often need repointing, rendering, roof repairs and window replacement, and loft conversions can work well. Gower stone cottages call for lime-based repairs, and estate homes commonly take extensions and driveways.
In Gorseinon, as elsewhere in West Glamorgan, we take the building's age and construction into account before recommending anything, because both can change what is involved in a double-storey extension.
Permissions for a double-storey extension in Gorseinon
Because Gorseinon falls under Wales's rules, the guidance below is the version relevant to you. Before sending a price, we check your property's position with the council.
In Wales, two-storey extensions are tightly limited under permitted development, including distance to the rear boundary, so most need planning permission.
Building Regulations approval is needed in Wales, and the Party Wall etc. Act 1996 applies to work on or near shared walls.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
What happens after you get in touch?
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 double-storey extension.
Written quote
We turn the survey notes into a written quote. The price is fixed for the specification we agree, and the document sets out materials, scope and payment stages in plain language.
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.
Finish and handover
On site, the agreed plan is followed and any change is put in writing first. At completion we do a final clean, go through the snagging list with you and leave you with the relevant documents.
Why homeowners choose us
Frequently asked questions
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.
What happens at the survey?
We visit your home at a time that suits you, look at the area involved, take measurements and check access, condition and any services that might be affected. We talk through what you want from a double-storey extension, explain the options and answer questions. There is no charge and no obligation; afterwards we send a written quote.
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.
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.
Which postcodes in Gorseinon do you cover?
We cover SA4, along with the rest of West Glamorgan. 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.
Nearby towns
We cover every part of Gorseinon, including SA4, and nearby Llanelli, Swansea and Clydach. Wherever you are within that patch, the survey is free and the quote comes to you in writing.