The short answer
Get at least three quotes from FMB-registered or building-control-approved garage conversion specialists, all on the same specification, and insist on an itemised written quote after a site visit rather than a phone-only price. Tell each builder the same brief — the room you want, the floor and insulation work, the services needed and who arranges building control — so the quotes are comparable. Then line them up item by item and weigh price alongside the scope, guarantee, survey quality and reviews. See how to choose a garage conversion builder for the checks that matter.
Getting quotes is the step where homeowners most often end up comparing apples with pears — one quote includes the floor and insulation properly, another leaves out making good or the building control sign-off. This guide explains what to tell builders, what a good quote should contain, and how to compare three quotes fairly. We are an independent information and introduction service: we do not carry out conversions, and we publish this guidance free.
Getting quotes at a glance
- How many At least three
- Same brief Identical spec to each
- Survey On-site, not phone-only
- Format Itemised, in writing
- Registration FMB or building-control-approved
- Compare on Like-for-like spec
What to tell each builder
To get comparable quotes, give every builder the same brief. The more precise you are, the less room there is for quotes to drift apart on hidden differences. Cover the room you want and its use, the floor work (raising and damp-proofing), insulation to the walls and roof, the services needed — electrics, heating and any plumbing — windows and the door infill, and who arranges building control. Ask each to survey the garage rather than quote over the phone, because a proper site visit is what makes a quote reliable.
| Tell the builder | Why it matters |
|---|---|
| Room and its intended use | The core of the quote — must match across all three |
| Floor and damp-proofing | Raising and damp-proofing the floor can change the price significantly |
| Insulation & door infill | Walls, roof and the garage door opening |
| Services needed | Electrics, heating and any plumbing for a kitchen or bathroom |
| Building control | Who arranges the inspections and completion certificate |
What a good written quote includes
A quote you can rely on is itemised and in writing, not a single headline figure. It should set out the room and its use, the floor and damp-proofing work, insulation to walls and roof, the door infill and windows, the services covered, who notifies and signs off the work under building regulations, the guarantee length and terms, and what is included for making good. If a quote is vague about any of these, ask for it to be spelled out before you compare. Sense-check the figures against our garage conversion cost guide.
How to compare quotes fairly
With three written quotes on the same brief, line them up item by item. A price gap often comes down to one quote including the floor and damp-proofing properly, a longer guarantee, or building control that another omitted — adjust for anything missing before judging on price. Sense-check the figures against typical costs in our garage conversion cost guide, then weigh the things price alone does not capture: the quality of the survey, the clarity of the guarantee, independent reviews and how the builder communicated. The cheapest quote is not automatically the best value, and the most expensive is not automatically the safest. These are general pointers, not advice for your specific job.
Compare garage conversion quotes
Get matched with FMB-registered or building-control-approved garage conversion specialists in your area, then apply these checks to compare on a like-for-like spec. Free to use, no obligation — we are an independent guide, not a builder.
Frequently asked questions
How many garage conversion quotes should I get?
At least three, all on the same specification — the same room, floor and damp-proofing, insulation, services and building control arrangement. This lets you compare fairly and spot a quote that is cheap only because it leaves something out.
Should I get a site visit or a phone quote?
Insist on an on-site survey. A proper site visit is what makes a quote reliable; a phone-only or online estimate can change significantly once a builder sees the garage, the floor and any work needed. A proper survey also lets you judge how the builder works.
What should a garage conversion quote include?
An itemised written quote should list the room and its use, floor and damp-proofing, insulation, door infill and windows, electrics, heating and any plumbing, building control notification and sign-off, guarantee terms, making good, and the deposit and payment schedule. Ask for anything vague to be spelled out.
Is the cheapest garage conversion quote the best?
Not necessarily. A lower price can mean a thinner scope — less insulation, no allowance for the floor, or omitted building control — while the dearest is not automatically the safest. Compare on a like-for-like specification and weigh the guarantee, survey quality and reviews, not just the headline figure.
Sources & further reading
- Federation of Master Builders (FMB) — finding and checking registered builders
- Local authority Building Control — inspection and completion certificates
- Planning Portal — permitted development for garage conversions
- GOV.UK / Building Regulations Approved Documents — standards for habitable rooms
This is general information, not advice for your specific situation, and not a quote. We are an independent information and introduction service — we do not carry out conversions or provide quotes ourselves; we can connect you with an FMB-registered or building-control-approved garage conversion specialist. Figures are typical illustrations, not quotes.