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 Gwent?
In Gwent, 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 |
The main things that change the cost:
- Cladding and finishes
- Drainage connection distance
- Kitchen and bathroom
- Heating type
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 garden annexe in Gwent?
The approval route for Gwent is set by planning law 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
The work we manage on a garden annexe:
- Glazed doors and windows
- Kitchenette and shower room
- Foundations and drainage connections
- Planning drawings and application
- External cladding or brickwork
- Insulated walls and roof
How long does it take?
Allow 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 Gwent
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Towns we cover in Gwent include Newport, Cwmbran, Pontypool, Ebbw Vale, Risca and Abergavenny.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 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 garden annexes in Gwent
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.
Who approves a garden annexe in Gwent?
Planning matters in Gwent go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
How long does it take?
Typically 10 to 16 weeks on site.
How much does a garden annexe cost in Gwent?
In Gwent, 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 Gwent?
In Wales an annexe with sleeping accommodation usually needs planning permission; outbuildings under permitted development must be incidental to the house.
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.