Garage conversions

Converting a garage into a habitable room requires a Building Regulation.  

A well-designed and constructed garage conversion can provide useful extra space and add value to your property. A poorly thought-out conversion however, can reduce your property’s value, and compromise your safety and the structural integrity of your home. It is important to ensure that you plan your garage conversion carefully and get the work carried out by an experienced contractor.

Planning permission and garage conversions

Most garage conversions can be completed under permitted development rights, particularly if you are not planning to alter the structure. But, you should check there are no planning conditions attached to the garage, particularly if you live in a: 

  • new build property
  • listed building
  • conservation area 

Some properties do not have the right to convert a garage. This might be because the council wants to keep parking areas (to prevent street parking) or because of the aesthetics of the street. 

If you change the structure or size of the garage you need to check with the council as it may fall outside of permitted development rights. 

Detached garages

If you are converting a detached garage, then you'll have to apply for a ‘change of use’ which needs building regulations approval.

Building regulations for garage conversions

All garage conversions need building regulations approval. To comply with building regulations your garage conversion must:

  • be structurally sound
  • have a damp-proof course
  • have energy efficient wall, floor and ceiling insulation
  • have had all electrics safety tested
  • be moisture proofed, with good ventilation
  • have been fire-proofed and have escape routes

Your local authority building control team will check that the correct doors and windows have been used, that the right drainage is in place and that all of the structural elements are suitable for the room you have created.

Your local authority building control team will also check the following:

Foundations

One of the main areas of concern will be the type of foundation in your current garage. In most cases, it is too shallow for the additional weight of a new wall, window or door where the garage door used to be. If the conversion doubles the height, the foundations need to be even deeper. 

The builder will need to dig out new foundations and you may have to engage a structural engineer to ensure the new foundations are correct.

Structural changes

As part of the conversion you may want to change the line of the roof or install new windows, doors, entrances or walls – both inside and out. If any of these affect the overall structure of the space, they will need to be approved first.

Thermal proofing

A garage isn’t made to be warm and cosy. In fact, ventilation and airflow are important in a garage so it will be draughty. 

The floors, walls and roof of your garage will need to be insulated and improved to ensure that you meet the minimum requirements for energy efficiency inside your new room. These rules also cover the windows and doors that are used.

Ventilation

Any new habitable rooms need adequate ventilation for health reasons. This is achieved by providing an opening window at least 1/20th of the floor area of the room. 

The windows should have: 

  • a trickle vent in the frame with a clear opening of at least 0.33m2
  • dimensions of at least 450mm x 450 mm

Drainage

If your conversion is going to have a bathroom or toilet you need to ensure that you have good access to drainage and that sewers are correctly used. 

You might also find that the garage has been built over existing drains. Your household plans may give you some insight into this.