A builder laying a wall of concrete blocks.

Guide

Building regulations for a garage conversion

What the inspector checks, which way to apply, what it costs with your council, and why the certificate at the end matters.

Published October 2026 · Researched and checked by Ben Criddle

The short answer

You will almost certainly need it.

Once a garage becomes a room you live in, building regulations apply. They check the room is built safely, warm and dry. An inspector visits at key stages, and you get a completion certificate at the end.

It is a normal part of every garage conversion, not an extra hurdle. The certificate is also what a buyer's solicitor asks for when you come to sell.

Solihull fee£570Building notice for a single garage, 2026/27, including VAT.
Inspections4 or 5Visits included in the fee in Warwick District and Coventry.
Certificate8 weeksYou usually get it within 8 weeks of finishing, says GOV.UK.

What does building control check on a garage conversion?

The checks follow the build, from the old doorway to the finished room.

The old doorway. A new wall fills the gap where the garage door was. It often needs its own foundation, and any drain running underneath has to be protected.
The floor. Garage floors have no damp barrier and sit low. A damp-proof layer and insulation go down, usually bringing the floor up to the level of the house.
Walls and ceiling. The garage was never heated, so once it becomes a warm room its walls and roof must reach today's insulation standard.
A way out in a fire. The room needs a door to a hall that leads outside, or an escape window. That window opens to at least 0.33 square metres, 450mm wide and high, with its bottom no more than 1.1 metres up.
Smoke alarms. Mains-powered smoke alarms in the hall and landing, so a fire in the new room is heard.
Fresh air. A way to ventilate the room, such as a window that opens and trickle vents.
Electrics. New circuits are fitted by a registered electrician, who certifies the work and gives you a certificate.
Drains. Only if you add a toilet or shower, which joins the house drains or uses a pump.

Behind each step is part of the official guidance, the Approved Documents: structure, fire, damp, fresh air, drainage, energy and electrics. Your builder and inspector work to those, so you do not need to read them.

Building notice or full plans?

There are two ways to apply. Both end with the same completion certificate.

Full plansDrawings are checked and approved before work starts. GOV.UK says to expect a decision within 5 weeks. The safer route when a wall opens into the house or a steel beam goes in.

Building noticeYou tell the council and can start 2 days later. Nothing is approved in advance; the inspector checks as the work goes. Suits a straightforward single garage.

Full plans are required if the new wall is built over or near a public sewer. That can happen where the old doorway is filled in. Drawings for full plans usually cost £1,200 to £2,500. Where a wall opens into the house, a structural engineer's calculations add about £500 to £1,200.

The council, or a private inspector?

Either is allowed. You can use your council's building control team, or a private registered building control approver, the new name for an approved inspector. Your builder will usually suggest one. Approval for work that has already been done is only available from the council.

How much does building control cost for a garage conversion?

For a single garage near us, between about £390 and £680, depending on your council. The fee covers the checks and the visits, and is paid to building control, not your builder.

Single garage conversion, fees from April 2026, including VAT, from each council's own published charges (checked 21 October 2026).

How many visits, and how long does it take?

The inspector comes at the stages that get covered up. That means the new wall's foundation, the floor before it is finished, the insulation, and the end. Coventry's fee includes up to 5 visits and Warwick District's up to 4.

Once the work is finished and passed, you usually get the completion certificate within 8 weeks.

Why the completion certificate matters

It is the proof that your new room was built to the rules. GOV.UK warns that without approval you will not have the certificates you may need when you sell. Lenders and buyers treat a room without one as a risk.

Keep it with the electrician's certificate and your planning paperwork, if you had any. Those three documents answer most questions a buyer's solicitor will ask about the room.

What if a conversion was done without building regulations?

It can be put right. The council can approve work after the event, called regularisation. It costs more, and the inspector may ask to see inside finished walls or floors. A council can also take action for up to 10 years after the work is finished; until October 2023 that limit was 12 months.

Solihull£620To approve a single garage conversion after the work is done.
Coventry£1,012.50To approve a single garage conversion after the work is done.
Warwick District£612.50To approve a single garage conversion after the work is done.
Bromsgrove and Redditch£472.56To approve a single garage conversion after the work is done.
Stratford-on-AvonPriced after a visitTo approve a single garage conversion after the work is done.

April 2026 charges, from each council's published fees. Approval after the event carries no VAT.

Building regulations for garage conversions: your questions

Do I need building regulations for a garage conversion?

Yes, in almost every case. Once a garage becomes a room you live in, such as a bedroom, office or kitchen, building regulations apply. The Planning Portal says a garage conversion will normally require approval under the building regulations.

Do I need building regulations to convert half my garage?

Yes, for the half that becomes a room. The room at the back is checked like any other conversion. The wall between it and the storage at the front has to resist fire for 30 minutes.

Does a detached garage conversion need building regulations?

Yes, if it becomes a room you live in or sleep in. Some small detached buildings used only for storage are exempt, but a habitable room is not. Services such as power and water to a detached garage are checked too.

Can I convert my garage without building regulations?

You can, but it causes problems later. Without a completion certificate, selling is harder and a council can act for up to 10 years after the work is finished. Approval can be applied for afterwards, but it costs more and may mean opening up finished work.

Who signs off a garage conversion?

Your council's building control team, or a private registered building control approver if you chose one. They visit at key stages and issue the completion certificate. The electrician certifies the electrics separately.

Do I need planning permission as well?

Usually not. Most garage conversions are permitted development, so they need building regulations approval but no planning application. Check if your estate's rights were removed or you live in a listed building or conservation area. Our planning permission guide.