Building Regulations Approval for Garage Conversions in Liverpool

Planning permission and Building Regulations are not the same thing

This is the most common mix-up we hear. Planning permission is about whether a change is acceptable in principle: how it looks, how the property is used, parking and neighbours. Building Regulations are about how the work is built: structure, fire safety, damp, insulation, ventilation, drainage and electrics. A garage conversion can need one, both or, rarely, neither, and the answers come from different teams at the council. Our page on planning and permitted development covers the first question; this page covers the second.

Getting building control right is a core part of every garage conversion we carry out in Liverpool, because it is what proves the room is a safe, legal part of the house when you come to sell.

Who approves the work?

You have a choice of building control body. One is the local authority building control team at your council: Liverpool City Council, Sefton, Knowsley, St Helens, Wirral or Halton, depending on where you live. The other is a Registered Building Control Approver, a private body registered under the Building Safety Act 2022 regime, which replaced the old “approved inspectors” from April 2024. Both check the work against the same regulations. Fees vary between councils and approvers, so we always suggest asking for the current fee for your job directly.

Full plans or building notice?

For many garage conversions, full plans gives the most certainty because the fire escape, structural and insulation details are agreed on paper before anything is built. Drawings for that application are prepared by an architect or architectural technician; our design and drawings page explains what they include.

Which parts of the Building Regulations usually apply?

• Part A – StructureFoundations or a lintel or beam for the garage door infill wall, lintels over new openings, and the stability of existing single-skin walls and piers.
• Part B – Fire safetyAn escape window where the room is an inner room, smoke alarms, and the fire separation between an integral garage and the rest of the house.
• Part C – DampA damp-proof membrane in the new floor that laps with the damp-proof course in the walls, and weatherproofing of single-skin walls.
• Part E – SoundSound insulation where the garage wall is shared with a neighbour, as on many linked and semi-detached garages.
• Part F – VentilationOpenable windows for purge ventilation, trickle vents, and extract fans in any shower room or WC.
• Part H – DrainageAny new waste pipes and connections to the drains.
• Part L – EnergyInsulation of the walls, floor and roof to the U-values building control asks for, plus efficient windows and doors.
• Part P – Electrical safetyNew circuits and sockets installed by a registered electrician who notifies building control.

What the inspector usually looks at, and when

1. Commencement. Building control is told before work starts, and the site visits are agreed.
2. Foundations or support for the infill wall. If a new foundation is dug for the infill, the trench is usually inspected before concrete goes in. Where the wall sits on a lintel or beam, the method is agreed with building control.
3. Damp-proofing. The floor membrane and its link to the existing damp-proof course, and the damp-proof course in the new wall.
4. Insulation. Wall, floor and roof insulation before it is covered by plasterboard or screed.
5. Drainage. New waste runs, tested before they are buried or boxed in.
6. Final inspection. Escape window, smoke alarms, ventilation, finished room and the electrical and other paperwork.

The exact stages depend on the job and the building control body. We work to the agreed drawings and book each stage so nothing is covered before it has been seen.

Integral garages need extra care with fire safety

Before conversion, the wall and door between an integral garage and the house usually provide fire separation, and the internal door is normally a fire door. After conversion the garage becomes part of the house, so the fire strategy for that whole floor is reviewed with building control: doors, the escape route, alarms and whether the new room is an inner room. Where it is, LABC guidance asks for an escape window with a clear opening of at least 450 mm × 733 mm and the bottom of the opening no more than 1.1 m above the floor. Never remove a fire door on your own judgement; building control will confirm what is needed.

The paperwork you should end up with

• A building control completion certificate (sometimes called a final certificate) for the conversion.
• An Electrical Installation Certificate to BS 7671 from the registered electrician, who also notifies building control under Part P. See electrics for garage conversions.
• Any Gas Safe paperwork if gas work was done, and commissioning records for heating.
• The approved drawings and any planning paperwork, if planning was needed.

Keep these with your house deeds. A buyer’s solicitor will usually ask for them.

What if an old conversion was never signed off?

We often see garages converted years ago with no completion certificate. An unapproved conversion can delay a sale. Options include regularisation, which is a retrospective application to your council’s building control team, where parts of the work may need opening up so they can be checked, or indemnity insurance arranged through your solicitor. Get advice from your solicitor before deciding. Our garage conversion problems guide lists the defects that often show up when an old conversion is opened up.

Building control across Liverpool and Merseyside

The council you deal with depends on your address. A conversion in West Derby or Woolton goes to Liverpool City Council unless you choose a registered approver; one in Maghull goes to Sefton; one in Widnes goes to Halton. The regulations are national, but each body has its own fees and procedures, which is another reason to talk early. As a local garage conversion specialist, we plan the job around whichever body you use and make sure your converted garage has the paperwork to show for it.