DATA-BACKED GUIDE · UPDATED JULY 2026
What drives the cost of a garage conversion
A garage conversion is one of the cheaper ways to add a proper room, but the final bill swings a lot depending on what the space needs before anyone touches the finishes. Two garages that look the same from the drive can cost very different amounts once you get past the plasterboard. Before you look at the real prices below, it helps to know which jobs quietly push the total up and which ones barely move it.
The quick version
- Most of the cost sits in insulation, damp-proofing and a new floor, not the finishes you actually see.
- An integral garage is usually cheaper to convert than a detached one because the services are close by.
- A garage conversion counts as building work, so expect 20% VAT on most of the labour and materials.
- Wet rooms cost more than dry ones. A kitchen or bathroom needs plumbing and drainage run in; a bedroom or office does not.
- What you do with the up-and-over door, keep it, brick it up, or fit a window in its place, changes both the look and the price.
- The real prices below come from actual prices, so you can see what people paid rather than a guess.
What people actually paid
Real prices, in people's own words
- £3,000“Ours was about £3k. We had to pay separately to have a new roof”
- £6,000“We have just had one done and it cost 6k.”
- £9,000“Mine was 9K. Internal garage, large for a single garage.”
- £10,000“Ours was around the 10k Mark”
- £10,000“We paid around £10,000 for the project. That included flooring too.”
- £15,000“We've just spent 15k on a double garage conversion in south wales”
Genuine amounts posted publicly. We publish the price and the quote, never the person.
Why the price varies so much
No two garages start from the same place, and that starting condition drives most of the spread you will see in the real prices on this page. A single skin wall needs lining and insulating to meet building regs, while a newer garage built in blockwork may need far less done to it. The floor is another swing factor, since many garages sit lower than the house and need building up and damp-proofing before anything else can go in. What you want the room to become matters too. A bedroom or home office is fairly straightforward, but a kitchen or bathroom needs plumbing and drainage run in, which adds a trade and adds cost. Whether you keep the up-and-over door, brick up the opening, or fit a window in its place changes both the look of the finished room and the labour involved. Who does the work affects price as well. A sole trader working alone will usually charge less than a small building firm with a project manager and a team, but the firm may move faster and carry more insurance. Location plays a part too, since labour rates and how busy local builders are both vary from one part of the country to another, which is part of why the same job can cost noticeably different amounts depending on where you live.
How to pay less
- Keep plumbing out of it where you can, since a dry room like an office or bedroom avoids the priciest work.
- Get three quotes from local builders and compare what each one includes for the floor and insulation, not just the headline figure.
- Reuse the existing opening rather than widening it, as structural changes mean beams and extra labour.
- If you pay a deposit, put it on a credit card so you get Section 75 protection if the firm folds.
- Ask for a fixed price rather than a day rate once the floor is opened up and the true condition of the slab and walls is known, so surprises do not turn into open-ended bills.
- Time the work for a quieter part of the year for builders if you can. A firm with a gap in its diary has more reason to sharpen its price than one booked up months ahead.
Common questions
Do I need planning permission for a garage conversion?
Usually not, as long as the work stays within the existing walls and you are not on a flat or in a conservation area. It almost always needs building regulations approval though, which covers insulation, fire safety and damp. Check with your council before you start, since the rules differ by area and by property type.
Does a garage conversion add value?
It can, especially when it turns a rarely used garage into a bedroom, office or family room. The gain depends on your area and whether buyers there still want off-street parking. In most streets a warm, usable room beats a cold store, but if parking is tight locally a lost garage can work against you at resale.
Why is my garage conversion quote so much higher than a friend's?
Starting condition is the usual reason. If your garage needs a new floor, extra damp-proofing or the wall built up to take insulation, that lands before any finishing even begins. What the room is becoming matters too, a plumbed kitchen or bathroom costs more than a dry bedroom or office. Compare the real prices below to see the spread and what each job involved.
Is it cheaper to convert an integral garage than a detached one?
Generally yes. An integral garage already shares a wall with the house, so electrics, heating and sometimes water are close by and easier to extend into the new room. A detached garage may need new supply runs dug in or routed round, which adds labour and materials before the room itself is even started.
What should be included in a garage conversion quote?
A proper quote should set out the floor build-up and damp-proofing, insulation to walls and roof, any structural work to the opening, first and second fix electrics, plastering, and what happens to the garage door. If a quote is vague on the floor or insulation, ask the builder to break it down, since that is usually where the real cost sits.
Do I need building control sign-off when it's finished?
Yes. Building regulations approval is separate from planning permission and covers things like insulation levels, fire safety and ventilation. You will need a completion certificate, so make sure your builder either works with a building control inspector directly or leaves you with the paperwork to arrange it.