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.
Whether you live in one of the larger towns, such as Llanelli, Ammanford, Aberystwyth and Carmarthen, or somewhere quieter in Dyfed, the way we handle a double-storey extension is identical. We survey, agree the specification with you, and confirm a fixed price on paper. Everything is planned under the regulations in force in Wales, and guide costs in Wales sit at £55,000–£110,000 with VAT.
- Guide price
- £55,000–£110,000 inc VAT
- Time on site
- 14–22 weeks on site
- Planning rules
- Wales
- Price level
- About 8% below the national guide
- Towns listed
- 4
- Survey
- Free, with a written quote
How much does a double-storey extension cost in Dyfed?
Use the table to gauge the cost of a double-storey extension in Dyfed 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 Dyfed |
|---|---|---|
| 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 |
What moves the price up or down:
- 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 do you get?
- Groundworks, foundations and below-ground drainage
- Insulated cavity walls with brick or render to match the house
- Scaffolding for the full build, erected and inspected
- Electrics, plumbing and heating by qualified trades, with certificates
- Windows, external doors, plastering and internal doors
- Building control inspections and completion certificate
Homes in Dyfed
Dyfed covers Carmarthenshire, Ceredigion and Pembrokeshire. Stone cottages and farmhouses under slate roofs are common, often rendered or colour-washed, as in Tenby's brightly painted terraces. Llanelli has Victorian industrial terraces, Aberystwyth and Carmarthen have Georgian and Victorian centres, and bungalows and newer estates surround most towns.
Stone homes often need lime render, repointing and roof slating repairs. Terraces suit loft conversions and extensions, and rural bungalows commonly take extensions, porches and driveways.
Atlantic weather brings strong winds, driving rain and salt to the coast, so exposure ratings matter when specifying render and pointing.
Planning and building rules in Dyfed
Which rules apply depends on where you live. For Dyfed, the answer is Wales, and the points below reflect that; we verify them with the council before quoting.
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.
From survey to handover
A visit to your home
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.
Price and scope agreed
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.
Plan and prepare
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 Dyfed property.
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.
How we work
Frequently asked questions
Do you cover Llanelli, Ammanford and Aberystwyth?
Yes. As well as Dyfed, we cover Llanelli, Ammanford and Aberystwyth and the rest of Dyfed. 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.
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.
Do I need planning permission for a two-storey extension?
Most two-storey extensions need planning permission, but it depends on the size, height and position, your home's location, whether it is listed or in a conservation area, and which UK nation you are in. In England, a two-storey rear extension can sometimes be built under permitted development if it is no deeper than 3m and at least 7m from the rear boundary. We check what applies before quoting.
How much does a double-storey extension cost?
A typical double-storey extension of 30–40m² across both floors costs £55,000–£110,000, 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.
Towns in Dyfed
These are the towns in Dyfed where you can book a free survey for a double-storey extension. Each has its own page with guide prices and coverage details.