Garden annexes in Barnet

Covering Barnet

Our coverage around Barnet (EN5) also includes Potters Bar (3 miles to the north) and Borehamwood.

Homes in London

Terraced houses dominate many London neighbourhoods, so most projects involve shared walls, narrow access and a party wall process. Conservation areas are widespread, and some boroughs have their own mansard and basement guidance.

What goes into a garden annexe?

We design annexes as permanent buildings with proper foundations, insulation and services, and we prepare the planning case showing how the annexe will be used as part of the main home. Connections for water, drainage and power are planned from the start.

Foundations and drainage connections
Brick, block or timber-frame structure
Accessible design options for older relatives

How much should I budget for a garden annexe?

Guide prices for garden annexes, including VAT where it applies. Your fixed price is confirmed in writing after the survey.

Garden annexes	Guide price incl. VAT
Standard specification	£2,400 to £2,900 per m²
Good specification	£2,900 to £3,400 per m²
High specification	£3,400 to £3,900 per m²

What approvals does a garden annexe need in England?

Projects in England go through two separate checks. Planning (or confirmation that the work is permitted development) comes from the district, borough or unitary council, and building regulations approval comes from the council’s building control team or a registered building control approver. Where work touches a shared wall or digs near a neighbour’s foundations, the Party Wall etc. Act 1996 applies.

A self-contained annexe used for sleeping and living normally needs planning permission in England.

What can affect a garden annexe?

Drainage may need a pump if the garden falls away from the sewer.
Council tax treatment depends on who lives there; check with your council.

What are the steps?

Send us the details. Give us a postcode, a rough idea of size and some photos, by phone, form or the guide price tool.
Free site visit. We measure up, look at access, drains and the structure, and talk through options and budget.
Drawings, approvals, written quote. We prepare the design, apply for the approvals it needs, and give you a fixed price in writing.
Construction and completion. One site lead co-ordinates every trade through to the building control certificate.

Your questions answered

Do I need planning permission for a garden annexe?

Usually yes, because people will sleep in it. Outbuilding permitted development does not cover living accommodation.

How much does a garden annexe cost?

Around £2,400 to £3,900 per square metre including VAT, depending on finish and services.

Do you work in Barnet?

Yes. Barnet is within our coverage for garden annexes, along with nearby Potters Bar and Borehamwood.

Garden annexes in nearby towns

Learn more about garden annexes, or see every project we cover in Barnet.