Garage Conversion Budget Planner
Work through a garage conversion in the order it happens, with the cost of each stage as you go.
Part of the 🏠 Homeowners and DIYers toolkit, with more tools made for the job.
Converting a garage usually needs sign-off under local building rules, and sometimes planning permission or a check of your property deeds. Rules on permits, building regulations and which work needs a qualified person differ by country and place, so check yours before you start.
Plan the conversion
The floor area of the garage lets you see the cost per square metre or foot at the end.
The floor area of the garage
Use this instead of length and width.
Plan it and check the rules
Before any work: drawings, approvals and anything that affects neighbours.
Make the shell sound
A garage is built to keep a car dry. The floor, the front and the structure usually need work first.
Insulate it
Walls, ceiling and floor all need insulating to suit a living space.
Run the electrics, heating and plumbing
Done before the walls are closed up. Electrics, gas and some plumbing need a qualified person in many places.
Plaster, floor and decorate
The finishes that make it feel like a room.
Clear up
Waste, and the things that crop up at the end.
Running it afterwards
Once it is done it can still cost something. This is not part of the cost above.
Your garage conversion, step by step
What each stage adds, and the total.
Type some prices in the steps above and the whole cost appears here, stage by stage.
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Give the floor area of the garage, then work down the page through each stage of the conversion, typing what each part costs. The total builds as you go, with a safety margin at the end.
A garage conversion looks simple because the walls and roof are already there, but the cost is in everything a garage does not have: insulation in walls, ceiling and floor, a proper floor level and damp protection, a front wall with windows where the door was, electrics, heating and plastering. Guides from builders' bodies and self-build sites list these same lines and note that labour is often 40 to 50 percent of a single garage conversion. Many places also require building control sign-off, and some need planning permission or a check of your property deeds. Going through the stages in order, from the rules to the final clear-up, shows you which lines are missing from the quotes you are given.
How it’s worked out
- Step 1, the floor area of the garage, so you can see the cost per square metre or foot at the end.
- Plan it and check the rules: drawings, building control fees, and a party wall agreement if you share a wall.
- Make the shell sound: removing the garage door, levelling and damp-proofing the floor, the new front wall and windows, and any structural work.
- Insulate, then run the electrics, heating and plumbing before the walls are closed up.
- Plaster, floor and decorate, then clear up. The summary adds a share kept back for surprises, 15 percent if you leave it empty.
Stages of 1,700 for planning, 4,250 for the shell, 2,200 for insulation, 2,950 for services, 2,250 for finishes and 500 to clear up come to 13,850. With 15 percent kept back the budget is 15,927.50, or about 995 a square metre on a 16 square metre garage.
Common mistakes
- Leaving out the floor. A garage floor is often lower than the house and not damp-proofed, so levelling and insulation can be a big line.
- Forgetting the front wall. Replacing the garage door with a wall and window takes materials, labour and often a lintel check.
- Skipping the fees. Building control, inspection and sometimes party wall costs are real lines that are easy to forget.
- Not asking what the quote leaves out. Quotes often exclude plastering, decorating, electrics or the skip, so check each stage against them.
Questions
Do I need planning permission to convert a garage?
It depends on the country and place. Many conversions that do not change the outside much do not need it, but some do, and conversions almost always need building control approval. Check with your local authority before you spend.
Why is insulation such a big stage?
A garage is built to keep a car dry, not to keep people warm. Walls, ceiling and floor all need insulating to a standard that suits a living space, and the floor is often the hardest part.
How much of the cost is labour?
Builders' guides often put labour at about 40 to 50 percent of a single garage conversion. Put it in the line it belongs to, or ask each quote to show it separately.
What about a bathroom or a kitchenette?
Adding plumbing and drainage adds a lot, and the right amount depends on where the pipes run. The services stage has a plumbing line, and the bathroom planner covers a full bathroom.
Where the method comes from
Estimates only
These are estimates and general information, not building, legal or professional advice. Costs, rules, permits and building regulations differ by country and place, so use your own quotes and check the rules where you live. Structural, electrical and gas work should be done by a qualified person.
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