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 Bletchley?
In Bletchley, a garden annexe typically costs £2,000–£3,150 per m² of floor area, including VAT at 20% (standard rate). For a typical 35 m² project that is roughly £70,000–£110,000. The guide for Bletchley reflects typical costs in the South East, roughly 12% above the UK-wide figure. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (24 m²) | £48,000–£75,500 |
| Typical project (35 m²) | £70,000–£110,000 |
| Larger project (49 m²) | £98,000–£154,500 |
| Rate per m² | £2,000–£3,150 |
Your quote will depend mainly on:
- Drainage connection distance
- Size and layout
- Access for materials
- Heating type
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a garden annexe in Bletchley?
The approval route for Bletchley is set by planning law in England. In England an annexe used as living accommodation usually needs planning permission. Outbuildings built under permitted development must be incidental to the house, such as a gym or office, not a bedroom.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
Handled as part of most garden annexes:
- Glazed doors and windows
- External cladding or brickwork
- Planning drawings and application
- Foundations and drainage connections
- Kitchenette and shower room
- Electrics and heating
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 Bletchley
The South East has a broad mix of housing, from Victorian terraces in the towns to post-war semis and newer estates, so extension types vary street by street.
Bletchley sits in Buckinghamshire, about 4 miles south of Milton Keynes. We cover the whole of Bletchley, including postcodes MK3.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about garden annexes in Bletchley
Does it need building regulations?
Yes, as it contains sleeping accommodation and services.
How long does a garden annexe take in Bletchley?
Typically 10 to 16 weeks on site. Design and approvals beforehand usually take 3 to 4 months.
How much does a garden annexe cost in Bletchley?
In Bletchley, a garden annexe typically costs £2,000–£3,150 per m² of floor area, including VAT at 20% (standard rate). A typical 35 m² project comes to roughly £70,000–£110,000. Your fixed price depends on the survey and drawings.
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.
Can it be accessible?
Yes. Level access, wider doors and a wet room can be designed in.