What will a garage conversion cost?
Turning a garage into living space is one of the best-value ways to add a room without an extension. Pick the garage — single, double, attached or detached — what it's becoming, the finish and your region, and we give you an indicative UK price range with heating, a knock-through to the house and the fees broken out. A number to plan around before you call a builder. Free, no sign-up.
A guide, not a quote. The ranges are typical 2025/26 UK all-in prices — building the floor up, insulating and dry-lining the walls and roof, infilling the garage door with a wall and window, electrics, decoration and the trades, inclusive of VAT — drawn from published industry averages. They exclude poor existing foundations, asbestos in an old garage roof, raising a low floor a long way, and a full annexe to building-regs habitable standard if the structure needs underpinning. The only real number is a measured, written quote from a builder, and you should get at least three. Nothing you type leaves your browser.
The new use sets the cost; plumbing is what makes it expensive.
A dry room is the cheapest win. Converting a single attached garage into an office, bedroom, playroom or gym is the bread-and-butter job: build the floor up over a damp-proof membrane, insulate and dry-line the walls and ceiling, replace the up-and-over door with an insulated wall and a window, run power and lighting, and decorate. That's where the lower end of the range sits, and it adds genuine living space for a fraction of an extension.
Plumbing changes the maths. The moment you add a kitchen, a bathroom or a self-contained annexe you're into drainage, supply pipes, waterproofing and a full fit-out — which is why those uses carry a higher multiplier here. An annexe with both a kitchen and a bathroom is effectively a tiny home and is priced accordingly.
Detached garages and knock-throughs cost more. A detached garage needs heating, water and drainage run to it across the garden. Opening the wall between the garage and the house to make open-plan living means a structural opening — a steel beam or lintel designed by an engineer and signed off — which is the single biggest add-on here.
Building regulations always apply. Even when the conversion is permitted development (no planning permission), it must meet building regs for insulation, damp-proofing, fire safety, ventilation and structural change. Budget for the building-control fees and, if there's a structural opening, a structural engineer. A converted garage that wasn't signed off can cause problems and cost money at sale.
Get three quotes — and check the floor. Prices for the same conversion vary between a general builder and a conversion specialist. Get three written quotes on a like-for-like spec, ask how they'll handle the floor level and damp-proofing (the most common shortcut), and tie payments to stages. A budget worked out in advance is your strongest negotiating position.
Keep your conversion project in one place.
Stead's home improvements log tracks the budget against what you actually spend, holds the building-control completion certificate, and keeps the receipts and guarantees you'll want at sale time — all alongside the rest of your home's record.