Carmarthen annexe extensions, designed and built
We design and build annexe extensions for houses in Carmarthen, with a written price once the survey and design are done and one point of contact throughout.
- Guide price in CarmarthenFrom £51,000 inc VAT
- PlanningUsually a planning application
- Build time16–24 weeks on site
- Postcode districtsSA31
Do I need planning permission in Carmarthen?
In Wales an annexe linked to the house and used by your household is assessed as an extension, but its size usually means a planning application is needed.
In a conservation area, national park, National Landscape or World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
The Party Wall etc. Act 1996 applies in Wales as in England: notice must be served before work to a shared wall, building on the boundary, or excavating close to a neighbour's foundations.
Building over or within 3 m of a public sewer needs the water company's consent before the foundations go in.
Applications are decided by the local planning authority (your county or county borough council, or the national park authority).
Local to Carmarthen
Across SA31, we can visit, measure and advise. Neighbouring towns we cover include Llanelli (13 miles), Ammanford (14 miles), Haverfordwest (29 miles), Pembroke Dock (29 miles).
Welsh housing ranges from stone terraces in the valleys to render-and-slate houses and modern estates, and the Welsh planning rules differ from England's in several places.
What should I budget for an annexe extension in Carmarthen?
Labour and material costs vary across the UK, so for Carmarthen we use our Wales factor (×0.93). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Carmarthen: £1,860 to £3,530 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Studio annexe 25 m² | £51,000 – £64,000 | £55,500 – £70,000 | £69,500 – £88,500 |
| One-bedroom annexe 35 m² | £65,000 – £81,500 | £78,000 – £98,000 | £97,500 – £124,000 |
| Larger annexe 45 m² | £83,500 – £105,000 | £100,000 – £126,000 | £125,500 – £159,500 |
Try the guide-price tool to see a range for your own size and finish.
Is an annexe extension right for your house?
- Homes with a large side or rear garden
- Relatives who need support close by
- Multi-generational families
Accessibility is cheaper to design in than to retrofit. Level access, a 900 mm door width, a level-access shower and space to turn a wheelchair can all be planned into the footprint for little extra cost.
How the project works
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
The price is fixed in writing once the design is settled, with a clear programme and payment stages.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions people ask about annexe extensions
Will my neighbours in Carmarthen be involved?
If a planning application is needed, the council notifies neighbours. If the work is on or near a shared boundary, party wall notices may also be needed.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Carmarthen, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Do you cover all of Carmarthen?
Yes. We cover Carmarthen and the surrounding parts of Dyfed. Site visits are free and there is no obligation.
Does an annexe extension need planning permission?
Usually yes, because of its size and the way it will be used. Councils check that it stays ancillary to the main house, so the application must describe the use clearly.
How much does an annexe extension cost?
Our guide range is about £1,860 to £3,530 per m² including VAT. A one-bedroom annexe of about 35 m² is typically £78,000 to £98,000 at standard spec in Carmarthen.
Book a free site visit in Carmarthen
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.