Garage conversion cost calculator
A garage conversion costs £7,500 to £12,000 for Single garage, basic room; £9,000 to £18,000 for Single garage, high spec and £12,000 to £20,000 for Double garage. Set the options below to price your own, adjusted for where you live.
Work out what converting a garage costs. Pick single or double and the level of finish, tick plumbing if the new room needs it, and this calculator gives you a price range for your region. Our own guide prices rather than quotes.
Garage conversion cost calculator
Set it up to match your job. Everything updates as you change it, and nothing is sent anywhere.
Built from the same figures as our garage conversion guide: £7,500 to £12,000 for a single garage finished as a basic room, £9,000 to £18,000 for a single garage to a high specification, and £12,000 to £20,000 for a double garage, with an en-suite or plumbing adding £2,500 to £6,000. The price covers insulating and finishing the floor, walls and ceiling, replacing the garage door with a wall and window, electrics, heating and plastering, and building control sign-off. Regional figures use the same multipliers as every other page here. Two things sit outside it and are worth checking before you budget. An integral garage often has a floor 100 to 150mm below the house, so levelling it up eats into head height and adds cost. And if the garage is your only off-street parking, converting it can affect what the house is worth in a way the build cost does not capture.
Garage conversion cost by region
| Conversion type | UK average | London | North / Scotland / Wales |
|---|---|---|---|
| Single garage, basic room | £7,500 to £12,000 | £9,800 to £15,500 | £6,900 to £11,000 |
| Single garage, high spec | £9,000 to £18,000 | £11,500 to £23,500 | £8,300 to £16,500 |
| Double garage | £12,000 to £20,000 | £15,500 to £26,000 | £11,000 to £18,500 |
Guide prices for garage conversion, before any extras. UK guide prices reviewed June 2026, not quotes. Set the calculator above to your own job to add the extras.
Why it is the cheapest room you can add
A garage conversion is the least expensive way to add a room to a house, and the reason is simple: the expensive parts already exist. There are foundations, four walls and a roof. You are not building a structure, you are making an existing one habitable, which is mostly insulation, a floor, a window where the door was, and first and second fix.
At £7,500 to £12,000 for a basic single garage, it typically costs a fraction of an extension of the same floor area. The comparison is not quite fair, because a single garage is only around 15m² and the shape is fixed, but if what you need is one more room rather than a bigger kitchen, it is usually the best value on the table.
The floor level problem
Most integral and attached garages were built with the floor 100 to 150mm lower than the house, deliberately, so that petrol or oil could not run inside. Converting means bringing that floor up to meet the house, and once you add the insulation building regulations now require, you can lose 200mm of head height before you start.
In a garage with a normal ceiling that is fine. In one with a low ceiling, or where the first floor sits above, it is the detail that decides whether the room feels like part of the house or like a converted garage. Measure the existing height before you get attached to the idea, and ask any builder quoting how they intend to handle the step.
Building regulations, damp and heat
A garage conversion always needs building control approval, even though it rarely needs planning permission. The regulations are mostly about making a cold, ventilated structure into a warm, dry one: insulating the floor, walls and roof to current standards, damp-proofing, providing ventilation and, if the room is a bedroom, a means of escape.
Damp is the usual surprise. A garage wall is often single skin, and a single-skin wall cannot simply be plastered and painted. It needs either an internal insulated stud with a cavity, or the wall rebuilding. A quote that does not mention what happens to the walls is worth questioning, because dot-and-dab straight onto single skin is exactly how a converted garage ends up with mould in the corners two winters later.
What it does to the value of the house
Converting a garage usually adds value, because habitable floor area is worth more per square metre than storage. The exception is where the garage is the only off-street parking, particularly in a city or anywhere with residents' parking. There, losing the parking can cost you more than the room adds.
It is worth a five-minute conversation with a local agent before committing. They will know whether buyers in your street expect a garage, and whether the road is one where parking is the thing people ask about first.
Common questions
How much does a garage conversion cost in the UK?
About £7,500 to £12,000 for a single garage finished as a basic room, £9,000 to £18,000 for a single garage to a high specification, and £12,000 to £20,000 for a double garage, with £14,000 the typical figure. Adding an en-suite or plumbing is another £2,500 to £6,000. London runs about 30% above the UK average and the North, Scotland and Wales about 8% below.
Do I need planning permission to convert a garage?
Usually not, if the work is internal and you are not enlarging the building. It is normally permitted development. You do always need building control approval, because you are turning an unheated structure into a habitable room and it has to meet current standards for insulation, damp-proofing, ventilation and escape. Some new-build estates carry a planning condition requiring the garage to stay a garage, so check your deeds.
How long does a garage conversion take?
Around 2 to 4 weeks for a single garage, which makes it one of the least disruptive ways to add a room. The work is mostly internal, so the rest of the house carries on as normal, and there is no scaffolding or groundwork. A double garage or one needing significant structural change to the opening takes longer.
Does converting a garage add value to a house?
Generally yes, because habitable floor area is worth more per square metre than storage space, and the build cost is low relative to the area gained. The important exception is where the garage provides the only off-street parking. In cities and streets with residents' permits, losing the parking can reduce the value by more than the extra room adds, so it is worth asking a local agent before you commit.
Can I convert a detached garage?
Yes, though it is a different job from an integral one. A detached garage needs its own heating and its own connection for power and, if you want plumbing, drainage, and it has more external wall exposed so it needs more insulation. It is often closer in cost and character to a garden room than to converting an integral garage, and it will not add to the house's habitable floor area in the way an attached conversion does.
These are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing. These are independent Costwise guide prices, reviewed June 2026, not quotes and not a survey of real quotes. A real price depends on access, condition and what the job actually involves, so use this to sanity-check what you are told and always get three written quotes.