Garage conversion: Tips from our building control experts

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Integral garage conversion in progress

A garage conversion doesn't always need planning permission as it often falls under 'permitted development'. But it's important to check permitted development rights still apply before starting any work, even if just for your client's sake.

Converting a garage will always need a building regulations application. A Building Notice application where detailed plans aren't needed will usually do, although a Full Plans application with a fully detailed specification will give you and your customer more security about what work needs to be carried out before you commence on site.

7 key considerations for a good garage conversion job

You must ensure the foundations are strong enough to carry any additional masonry loads. A new inner skin on the external wall or filling in the garage door with brick & block and a window will all add extra weight. Check the condition and suitability of the existing foundation or floor when the door infill area is excavated. If there isn't a foundation below the existing garage door you could carry the new wall off a suitable lintel - talk to your building control surveyor.

1. Walls

Check the existing walls for stability and make sure there aren't any defects. If satisfactory, then your building control surveyor is likely to consider it suitable for structural purposes. If it's single skin with piers and the piers are  being removed, the wall will be weakened and should be tied to a new inner leaf using remedial wall ties.

2. Weather

If you're dealing with a wall of single leaf construction, you must treat to make it weatherproof. Treatment options include tanking the wall using a vapour permeable membrane linked to a damp proof course or membrane at floor level, or providing a lightweight blockwork inner leaf with insulation in the new cavity. In all wall types, care must be taken to ensure the floor membrane laps with the DPC in the existing walls.

3. Insulation

You must insulate the walls, roof and floor to habitable standards, your building control surveyor or designer will help you choose the right insulation. Remember that you may need to add or increase ventilation to the roof voids. Where lining the garage with an independent stud partition, the insulation should be fitted tightly between the studs - using insulated plasterboard is best to avoid cold bridging.

4. Ventilation

Windows must have openable vents of an area equal to 1/20th of the floor area of the room. You also need 5,000mm2 of trickle vents to provide background ventilation. And if the new room can only be accessed via another room, a window with a clear opening of 450 x 733mm is a must for means of escape.

5. Sound

Any party wall between the garage and an adjoining property will need to be insulated to stop sound transmission. Check the existing wall construction - anything less than 200mm of dense blockwork will usually need further work, which may include additional masonry or specialist independent acoustic partitions – your building control surveyor will be able to advise you further.

6. Electricity

The requirements of Part P - Electrical safety in dwellings will apply to the new conversion, so ensure any installations are compliant and certified to BS 7671.

Your building control surveyor should be able to provide practical guidance on site.

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Did you find this article useful?

Further details on garage conversions can be found on the LABC Front Door website.

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Please Note: Every care was taken to ensure the information was correct at the time of publication. Any written guidance provided does not replace the user’s professional judgement. It is the responsibility of the dutyholder or person carrying out the work to ensure compliance with relevant building regulations or applicable technical standards.


(No subject)

Submitted 3 years ago

Would converting a garage always need Building Regulations approval? If it is a detached building, and < 30sq.m. in floor area, then surely converting it to, say, an office or games room would not need approval?


Submitted 3 years ago

The detached, exempt garage would indeed remain exempt unless it was used as sleeping accommodation, made two-storey, or undergoing a change of use as described in the Building Regulations 2010: Hotel, shop, residential, public building etc.

Providing a water service or electric to the exempt building would need approval, but only for that aspect of the work.

All attached (non-exempt garages would need approval).

Water service

Submitted 11 months 3 weeks ago

Who do I contact in regards to persmission to provide water to my detactched garage?


Submitted 11 months 1 week ago

You would submit a building regulations application to your local authority building control department. There's some information here on how to do that:

Kind regards
Julie, LABC

(No subject)

Submitted 3 years ago

It would be worth adding the following fire safety issues
1) If the conversion is the creation of a new habitable room without a door directly to outside the circulation spaces of the dwelling should be provided with mains wired smoke detection.
2) If the garage conversion is a habitable room accessed through another room a window should serve the conversion room meeting the criteria for escape .

(No subject)

Submitted 3 years ago

I saw this article on twitter today 25/02/16, the photo illustrates a detached structure. A converted detached garage complying with floor area and combustibility requirements would still be classed as an exempt structure provided there is NO sleeping accommodation. Think of garden rooms, home offices, hobby rooms?

(No subject)

Submitted 3 years ago

My attached garage has a solid slab concrete floor that is 150 mm lower than the house floor
I'd like create a new raised floor over a DPM by using raised, treated timber joists with infill insulation and chip board floor boarding with no under floor ventilation (since there is insufficient space)
Can yo tell me please if that will be acceptable to building control
David Ford

(No subject)

Submitted 3 years ago

Good idea about seven key considerations for a good garage conversion job. I agree with you. Can you tell me about cost?

(No subject)

Submitted 3 years ago

I would like to put a stud-work partition wall with door inside my internal garage to create a separate workshop area. The garage will still be used for storage etc. and workshop for hobbies. Would I need planning permission for this?


Submitted 3 years ago


Although it's unlikely that you'll need Planning Permission for the work, you're best to check with your local Planning Authority.

In relation to Building Regulations, this is minor work and you probably won't need a Building Regulation application.

To confirm this, I would suggest that you forward a sketch of the proposed layout to your local building control team. (Enter your post here to find their contact details


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