How much does an annexe cost?
An annexe typically costs anywhere from about £75,000 to £260,000+, depending on whether it’s a conversion, modular, hybrid or full new build
How much does an annexe cost?
An annexe typically costs anywhere from about £75,000 to £260,000+, depending on whether it’s a conversion, modular, hybrid or full new build.
With the latter options, it’s important to calculate the full turn-key cost. Turn-key costs tend to include all planning/ certification costs, a proper foundation, a service trench and connection to at least three services (ideally 4).
Garage Conversions are £40,000-£100,000 but are often compromised options although they offer a cheap and quick alternative to an overcrowded or inaccessible home.
Modular annexes and hybrid annexes are normally £80,000–£180,000 with a turn-key service with many one-bed options advertised from around £90,000–£125,000 including site-specific extras.
Traditional brick-built or permanent annexe: are commonly £150,000 for a small project with larger 45 m² annexes estimated around £190,000
Ensure that turn-key quotes include extras to watch for are groundworks/foundations, utility connections, drainage, planning/design fees, VAT status, access for delivery, and note Council Tax implications.
Many advertised prices exclude groundworks and mains connections, which can add around £20,000–£40,000 in many cases.
For a proper self-contained one-bed annexe, I’d budget £85,000–£120,000 all-in.
Request the 2026 Garden Annexes Brochure & Price List
