Garage conversion cost UK: the headline figures
| Type | Usable floor area | Total cost (London & South East) | Cost per m² |
|---|---|---|---|
| Single garage | ~15 m² | £10,000–£20,000 | £650–£1,350 |
| Double garage | ~30 m² | £15,000–£30,000 | £500–£1,000 |
A double garage conversion costs less per square metre than a single because the fixed costs, filling the door opening, connecting services, and preliminaries, are spread over twice the floor area. The job itself (floor build-up, wall lining, electrics) scales directly with size, but the one-off costs don't double, so the rate per m² falls.
These are indicative prices, current as at publication, not a quotation for a specific job, every garage is different, and the only way to get an exact figure for yours is a proper basic construction estimate priced from your own drawings.
What our garage conversion prices include (and what they don't)
Every garage conversion cost figure on this page includes labour, materials, our builder's margin and 20% VAT. Nothing is added on top: there's no separate labour line, no hidden overhead, no VAT to add at the end. This page prices a garage conversion as a job on its own, start to finish, preliminaries and protection, strip-out, the conversion work itself, making good, plastering, decorating and cleaning are all in the figures above.
What isn't included:
- Engineer and building control fees, separate professional and statutory lines, covered below.
- Provisional sums, windows, external doors, kitchen units, sanitary ware, floor and wall tiles, and internal door furniture are budgets the homeowner sets, not a price we fix. See the provisional sums section below.
- Contingency, our figures carry no contingency allowance; hold your own back for what the job might turn up once it's opened up.
Garage conversion cost per m²: single vs double
A single garage conversion costs £650–£1,350 per m², and a double costs £500–£1,000 per m², both well below the typical cost per m² of a new extension, because a garage conversion needs no new foundations, no new roof, and only one new external wall section (the former door opening) rather than three entirely new walls. If you're weighing a conversion against building out instead, our guide to pricing an extension walks through that cost from scratch.
Garage conversion cost by UK region
Our £10,000–£20,000 and £15,000–£30,000 figures are London and South East prices. Outside London, labour costs less and the same job typically costs less across the UK:
| Region | Single garage | Double garage |
|---|---|---|
| London & South East | £10,000–£20,000 | £15,000–£30,000 |
| East of England | £9,000–£18,500 | £14,000–£27,500 |
| South West | £9,000–£17,500 | £13,000–£26,500 |
| Midlands | £8,500–£17,000 | £13,000–£25,500 |
| Yorkshire and the Humber | £8,500–£16,500 | £12,500–£25,000 |
| North West | £8,500–£16,500 | £12,500–£25,000 |
| Wales | £8,000–£16,500 | £12,500–£24,500 |
| Scotland | £8,500–£17,000 | £13,000–£25,500 |
| North East | £8,000–£16,000 | £12,000–£24,000 |
| Northern Ireland | £7,500–£15,000 | £11,500–£22,500 |
The 12 phases of a garage conversion and what each one costs
Builder Expert prices every job, garage conversions included, through the same 12 phases in build order. Walking a single 15 m² garage conversion (about 5 m × 3 m) through them, with the finishing done to a habitable standard, shows where a realistic £10,000–£20,000 garage conversion cost actually comes from:
| Phase | What happens on a garage conversion | Rounded cost band |
|---|---|---|
| Preliminaries | Protection, skip, welfare, site health and safety, final clean | £1,250–£2,000 |
| Demolition | Remove the garage door, old flooring and ceiling, break up and clear the concrete slab | £750–£1,250 |
| Structural Flooring | New damp-proof membrane, insulation and screed across the floor | £750–£1,250 |
| External Walls | Fill the door opening with a new wall, lintel, cavity closers and one window | £1,250–£2,000 |
| Joinery | Internal door, architraves, skirting | £500–£1,000 |
| Plumbing and Heating | One radiator with pipework (more if a WC or kitchen is added) | £500–£750 |
| Electrics | Sockets, lighting, smoke alarm, consumer unit connection, electrical certificate | £750–£1,250 |
| Plastering | Insulated plasterboard and skim to walls and ceiling | £2,500–£3,500 |
| Decorating | Preparation and two coats of emulsion to walls and ceiling, woodwork in eggshell | £500–£1,000 |
| Finishes | Flooring to the finished room | £500–£1,000 |
| Provisional Sums | Window and door budget set by the homeowner (see below) | varies |
These phase bands sit within Builder Expert's own £10,000–£20,000 single garage conversion cost once the window and door budget is added, where exactly the job lands depends on the finish specified and whether a WC, kitchen or extra heating is added.
Preliminaries typically run at 10–15% of the total on a job this size and are already inside every figure quoted on this page, not an extra; our preliminaries guide explains what that percentage actually buys. Demolition and strip-out, removing the garage door, old ceiling and flooring, and breaking out the concrete slab, typically accounts for a small single-figure to low double-figure percentage of the job. A quote with nothing meaningful against demolition has almost certainly missed work.
Where the money actually goes: floor, walls, door opening and services
A garage conversion costs far less than an extension of the same size because the shell already exists: no new foundations and no new roof are needed, and the only new external wall is built where the garage door used to be, filled with blockwork, a lintel, cavity closers and typically one window. That single difference is why the garage conversion cost per m² sits so far below an extension's.
The floor is usually the first surprise. Garage slabs normally sit below the house's internal floor level and below the damp-proof course, so the slab is either broken out or built up with a new damp-proof membrane, insulation and screed. This is priced by the square metre, so it scales directly with the size of the garage, a double garage floor costs roughly double a single's to build up.
Walls and ceiling are priced the same way: insulated plasterboard and skim, per square metre of wall and ceiling. A long, narrow garage costs more to line than its floor area alone suggests, because the wall area is driven by the perimeter, not the footprint. A single-skin block garage also needs more insulation build-up than one already built in cavity brick, which pushes the cost towards the top of the range.
Turning the garage into a bedroom, office, utility or shower room
What the room becomes changes the number more than its size does:
- A home office or bedroom needs little beyond the core conversion: floor, walls, electrics, heating and decorating. This is the cheapest upgrade and sits at the lower end of the £10,000–£20,000 range.
- A WC or shower room adds a soil pipe, cold and hot feed and waste points, an extractor fan, tiling and sanitary ware fitting, each priced per fitting and per point, pushing the job towards the middle or top of the range.
- A kitchen or utility room adds a sink, worktop, units fitting, ventilation and appliance connections, again priced per item, and the units themselves are a provisional sum (see below).
- Heating can mean a radiator with pipework per room, a heated towel rail in a shower room, or underfloor heating priced per square metre of floor.
Only one of a combi boiler or a hot water cylinder is ever needed, never both, and whichever one your garage conversion needs pushes the job towards the top of the range. The same applies to the fuse board: if the existing consumer unit has no spare capacity, a small additional consumer unit is needed, another item that moves a conversion upward.
An electrical certificate (Part P) is issued at the end of the job, and a gas safety certificate where gas work is involved, both are inside our figures, not an extra.
Windows, kitchens and fittings: how provisional sums really work
Builder Expert does not price external doors, windows, kitchen units, sanitary ware, floor and wall tiles, or internal door furniture. These are provisional sums: a budget the homeowner sets, not a rate we fix, because the choice of product varies so widely. What's rarely explained is what happens to that budget once it reaches site.
Our builder's margin and VAT still apply on top of whatever budget you set, so a provisional allowance typically ends up costing about 1.44 times its value. A £7,000 kitchen allowance, for example, ends up costing roughly £10,080 once margin and VAT are added. The same mechanism applies to windows and external doors, sanitary ware, and tiling.
For the window and door set that fills a garage's old door opening, the current UK market average for supplying and installing a window and/or door set typically runs from around £1,000 to £3,000 depending on size, material and glazing spec, this is a market average, not a Builder Expert price, and the 1.44x rule applies to whatever figure you actually set as the budget.
Worked example: a 15 m² single garage converted to a home office
Assume a single garage, 5 m × 3 m (15 m²), converted to a home office with no WC or kitchen added. The job runs through preliminaries, demolition, structural flooring, external walls (door opening filled with a wall and one window), joinery, electrics, plastering, decorating and finishes, with no plumbing beyond a single radiator, and no fitting-out beyond what's already covered under electrics.
Adding the phase bands above gives £9,250–£15,000 for the core conversion. A homeowner's window budget on top, say £1,000–£2,000 set as a provisional sum, costing about 1.44 times that once margin and VAT are applied, brings the job to roughly £10,700–£17,900, inside Builder Expert's £10,000–£20,000 range for a single garage conversion in London and the South East. Scaling that same example by the North East's regional factor of around 80% puts it at roughly £8,500–£14,500.
Planning permission, Building Regulations and the fees to allow for
Most garage conversions that keep the existing footprint and don't create separate living accommodation are permitted development and don't need planning permission.
There are three common exceptions. Permitted development rights are often removed on newer estates and in conservation areas through an Article 4 direction. Some properties carry a parking condition that requires the garage space to stay a garage. And converting a garage into a self-contained annexe is a different use that needs a full planning application. The Planning Portal advises checking with your local planning authority before starting work, particularly on newer developments.
A change of use from garage to habitable room is a Building Regulations matter in essentially every case, whatever the planning position. Building Control checks:
- Structure over the new opening
- Thermal performance of the floor, walls and roof
- Damp-proofing and ventilation
- Fire separation and escape, particularly where the garage is integral to the house
- Electrics under Part P
Our guide to UK Building Regulations covers what Building Control looks for in full.
Fees sit outside our figures, as market prices:
- Building control, a building notice or full plans application for the change of use, typically a few hundred pounds depending on the local authority.
- Structural engineer, needed where the door opening is widened or a lintel is specified, typically a few hundred pounds for a single calculation.
- Lawful development certificate, for proposed work relying on permitted development, £264 in England.
- Householder planning application, where a full application is needed, £528 in England.
Both fees have applied since 1 April 2025, and the certificate fee is exactly half the application fee.
VAT on a garage conversion
A standard garage conversion attached to or occupied with a dwelling is standard-rated at 20% VAT, it is not a non-residential conversion, so none of the reduced or zero-rating available for genuine change-of-use projects applies. HMRC's VAT guidance on construction confirms that converting a garage occupied together with a dwelling into part of that dwelling doesn't qualify as a non-residential conversion. VAT is already included in every figure on this page, so there's nothing to add when you compare our numbers to a builder's quote.
Full detail sits in HMRC's VAT Notice 708 if your accountant needs to check the exact wording.
Integral, detached and partial conversions: what changes the price
An integral garage shares a wall with the heated house and usually sits close to existing electrics and plumbing runs, so services are cheaper to extend, this type typically lands towards the lower end of the regional ranges above. A detached garage is exposed on all sides, needs longer service runs from the house, and may need its own heating source and a separate consumer unit connection, pushing it towards the top of the range.
A partial conversion, keeping a store or utility space at the front behind the retained garage door, doesn't save as much as it might seem. The usable room shrinks, but the costly items (the door opening, the floor build-up, the services run, the dividing partition) stay in the job regardless, so the cost per m² of finished room actually rises compared with converting the whole garage.
Is it cheaper to convert a garage or build an extension?
Yes, converting a garage is cheaper per square metre than building the same floor area as a new extension, because a single garage conversion costs £650–£1,350 per m² and a double £500–£1,000 per m², against the much higher per-m² cost of a new extension. The saving comes from what you don't have to build: no new foundations, no new roof, and three fewer external walls, since the garage already has three sides and only the door opening needs filling. For the cost of building the same space from scratch, see our guide to pricing an extension.
A loft conversion is worth comparing too if floor space rather than a specific room is the goal, see our loft conversion cost guide for those figures.
Hidden costs and the contingency to hold back
Our figures carry no contingency. Hold your own allowance on top, specifically for what tends to open up once the slab and walls are exposed: damp coming up through an old, unprotected floor; a lintel over the door opening that isn't up to current standards; or a floor level that doesn't match the house and needs more build-up than planned. Our guide to hidden renovation costs covers the pattern across every type of job, not just garages.
One more to flag: where an older garage has an asbestos cement roof or wall panels, removal is a separate specialist job, priced and arranged outside the figures on this page.
Getting an accurate garage conversion estimate
These figures are Builder Expert's own, from real estimates, and give a realistic garage conversion cost range for planning purposes, but every garage has its own quirks, from floor level to wall construction to what's already nearby in terms of services. To compare two builders' quotes fairly, ask each one to itemise preliminaries, demolition, the floor build-up, the external wall and window, plumbing and electrics, plastering and decorating, and any provisional sums separately, not as one lump figure.
For an exact number against your own drawings, start with a basic construction estimate, or see our full construction estimating services if you're pricing this alongside other work. If you'd rather price the job yourself, our construction cost calculator is built for exactly that. And whichever builder you choose, our guide to comparing builder quotes is worth reading before you sign anything.
FAQ
How much does a garage conversion cost in the UK?
A single garage conversion costs £10,000–£20,000 and a double costs £15,000–£30,000 in London and the South East, with lower regional figures across the rest of the UK, as shown in the table above. These are Builder Expert's own indicative figures, including labour, materials, margin and VAT.
What is a garage conversion cost per m² and how does it compare with an extension?
A single garage costs £650–£1,350 per m² and a double £500–£1,000 per m², well below a typical extension's cost per m², because there's no new foundation, roof or three new walls to build.
What would it cost to convert a garage into a bedroom, office, utility or shower room?
A bedroom or office is the cheapest option, sitting towards the lower half of the £10,000–£20,000 range. A shower room or kitchen adds plumbing, tiling and fittings, pushing the total towards the top of the range.
What does the price include, and what's separate?
Our figures include labour, materials, margin and VAT for the conversion job itself, start to finish. Building control and structural engineer fees, planning fees, and provisional items like windows, kitchen units and sanitary ware sit outside the figures.
Do you need planning permission for a garage conversion?
Usually not, if the footprint stays the same and it doesn't become separate living accommodation, most fall under permitted development. Article 4 directions, parking conditions and annexe conversions are the main exceptions.
What does Building Control check, and what do the fees cost?
Structure, insulation, damp-proofing, fire separation and electrics under Part P. Building control fees are typically a few hundred pounds; a lawful development certificate is £264 and a householder planning application £528.
Is it cheaper to convert a garage or build an extension?
Yes, a garage conversion costs less per m² than an extension of the same size, because the walls and roof already exist.
Is VAT charged on a garage conversion?
Yes, at the standard rate of 20%, already included in every figure on this page.
What's the cost difference between an integral and a detached garage conversion?
Integral garages typically land at the lower end of the range because services are nearby; detached garages land towards the top because of longer service runs and extra insulation.
What are the hidden costs that push a garage conversion over budget?
Damp in the slab, an inadequate lintel over the old door opening, and a floor level mismatch with the house are the three most common, hold your own contingency for them, as our figures don't include one.
Last reviewed: October 2026.