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 Chelmsford?
In Chelmsford, a garden annexe typically costs £1,900–£2,950 per m² of floor area, including VAT at 20% (standard rate). For a typical 35 m² project that is roughly £66,500–£103,000. Prices across the East of England are typically 6% above the UK average for this kind of work, which is reflected in the range for Chelmsford. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (24 m²) | £45,500–£71,000 |
| Typical project (35 m²) | £66,500–£103,000 |
| Larger project (49 m²) | £93,000–£144,500 |
| Rate per m² | £1,900–£2,950 |
Your quote will depend mainly on:
- Kitchen and bathroom
- Access for materials
- Cladding and finishes
- 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 Chelmsford?
Approvals for a garden annexe in Chelmsford follow the rules for 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
From survey to sign-off, the job normally involves:
- Electrics and heating
- Glazed doors and windows
- Foundations and drainage connections
- External cladding or brickwork
- Planning drawings and application
- Building control sign-off
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 Chelmsford
Many towns in the East of England have estates built since the 1970s, where garage conversions and rear extensions are popular.
Our Chelmsford coverage includes postcode districts CM1 and CM99, and we also work in nearby places such as Billericay, Witham and Maldon.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 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 Chelmsford
Does a garden annexe need planning permission?
Usually yes if it is used as living accommodation. Outbuildings under permitted development must be incidental to the house, such as a gym or office, not bedrooms.
How much does a garden annexe cost in Chelmsford?
In Chelmsford, a garden annexe typically costs £1,900–£2,950 per m² of floor area, including VAT at 20% (standard rate). A typical 35 m² project comes to roughly £66,500–£103,000. Your fixed price depends on the survey and drawings.
How long does it take?
Typically 10 to 16 weeks on site.
Do you build garden annexes in Chelmsford?
Yes. We build garden annexes across Chelmsford, including postcodes CM1 and CM99. Every project starts with a free home visit.
Does it need building regulations?
Yes, as it contains sleeping accommodation and services.