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 Gainsborough?
In Gainsborough, 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. Building costs in the East Midlands run about 5% below the UK average, and the figures for Gainsborough are adjusted to reflect that. 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 |
Your quote will depend mainly on:
- Kitchen and bathroom
- Access for materials
- Cladding and finishes
- Drainage connection distance
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 Gainsborough?
The approval route for Gainsborough 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.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
Handled as part of most garden annexes:
- Planning drawings and application
- Foundations and drainage connections
- Glazed doors and windows
- External cladding or brickwork
- Kitchenette and shower room
- Electrics and heating
How long does it take?
The build itself usually takes 10 to 16 weeks on site. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in Gainsborough
The East Midlands has a mix of red-brick terraces, inter-war semis and newer estates, so rear extensions and garage conversions are common projects.
Projects in Gainsborough (DN21) are surveyed in person before we quote, so the price reflects your actual property.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about garden annexes in Gainsborough
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.
How long does it take?
Typically 10 to 16 weeks on site.
Who approves a garden annexe in Gainsborough?
Planning matters in Gainsborough go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
How much does a garden annexe cost in Gainsborough?
In Gainsborough, 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.
Can it be accessible?
Yes. Level access, wider doors and a wet room can be designed in.