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 Lancashire?
In Lancashire, a garden annexe typically costs £1,700–£2,650 per m² of floor area, including VAT at 20% (standard rate). For a typical 35 m² project that is roughly £59,500–£93,000. That range is adjusted for the North West, where domestic building work typically costs around 6% below the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (24 m²) | £41,000–£63,500 |
| Typical project (35 m²) | £59,500–£93,000 |
| Larger project (49 m²) | £83,500–£130,000 |
| Rate per m² | £1,700–£2,650 |
The main things that change the cost:
- Cladding and finishes
- Heating type
- Kitchen and bathroom
- Size and layout
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a garden annexe in Lancashire?
Before anything is built in Lancashire, we confirm which approvals apply 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.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
On a typical garden annexe we handle:
- Insulated walls and roof
- Planning drawings and application
- Electrics and heating
- Foundations and drainage connections
- External cladding or brickwork
- Kitchenette and shower room
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 Lancashire
The North West has many brick terraces and inter-war semis, where kitchen extensions and dormer loft conversions add space without moving.
Towns we cover in Lancashire include Preston, Burnley, Blackburn, Blackpool, Fylde and Rossendale.
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
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about garden annexes in Lancashire
Do you build garden annexes in Lancashire?
Yes. We build garden annexes across Lancashire, including postcodes BB1, BB10, BB11, BB12 and BB18. Every project starts with a free home visit.
How much does a garden annexe cost in Lancashire?
In Lancashire, a garden annexe typically costs £1,700–£2,650 per m² of floor area, including VAT at 20% (standard rate). A typical 35 m² project comes to roughly £59,500–£93,000. Your fixed price depends on the survey and drawings.
How long does it take?
Typically 10 to 16 weeks on site.
Does it need building regulations?
Yes, as it contains sleeping accommodation and services.
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.