What is a garden annexe?
A garden annexe is a single-storey building in the garden with its own living space, bathroom and often a kitchenette, used by relatives, older children or guests. Unlike a garden room, it is built as habitable accommodation with foundations, insulation and services.
How much does a garden annexe cost in Merthyr Tydfil?
In Merthyr Tydfil, a garden annexe typically costs £1,650–£2,600 per m² of floor area, including VAT at 20% (standard rate). For a typical 35 m² project that is roughly £58,000–£91,000. That range is adjusted for Wales, where domestic building work typically costs around 8% below the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (24 m²) | £39,500–£62,500 |
| Typical project (35 m²) | £58,000–£91,000 |
| Larger project (49 m²) | £81,000–£127,500 |
| Rate per m² | £1,650–£2,600 |
What moves the price most:
- Drainage connection distance
- Heating type
- Size and layout
- Access for materials
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a garden annexe in Merthyr Tydfil?
Whether you need planning permission depends on your house and its location in Wales. In Wales an annexe with sleeping accommodation usually needs planning permission; outbuildings under permitted development must be incidental to the house.
Building regulations in Wales are set by the Welsh Government. Approval comes from the council’s building control service or a registered building control approver, with inspections during the work and a completion certificate at the end.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
On a typical garden annexe we handle:
- Kitchenette and shower room
- Insulated walls and roof
- Building control sign-off
- External cladding or brickwork
- Electrics and heating
- Glazed doors and windows
How long does it take?
Expect 10 to 16 weeks on site. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Merthyr Tydfil
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
Projects in Merthyr Tydfil (CF47) are surveyed in person before we quote, so the price reflects your actual property.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about garden annexes in Merthyr Tydfil
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.
Will council tax apply?
Annexes can be banded separately, though discounts or exemptions apply in some cases when occupied by family. Check with your council.
Does it need building regulations?
Yes, as it contains sleeping accommodation and services.
How much does a garden annexe cost in Merthyr Tydfil?
In Merthyr Tydfil, a garden annexe typically costs £1,650–£2,600 per m² of floor area, including VAT at 20% (standard rate). A typical 35 m² project comes to roughly £58,000–£91,000. Your fixed price depends on the survey and drawings.
Do I need planning permission for a garden annexe in Merthyr Tydfil?
In Wales an annexe with sleeping accommodation usually needs planning permission; outbuildings under permitted development must be incidental to the house.
How long does a garden annexe take in Merthyr Tydfil?
Typically 10 to 16 weeks on site. Design and approvals beforehand usually take 3 to 4 months.