Garage Conversions

Garage conversions have been popular for a long time, its little wonder as most garages are glorified sheds! most modern garages can be readily converted into space you can enjoy, this post focuses on what you need to do to make this work for you.

Does a Garage Conversion need a Building Warrant?

Yes, is the short answer, as it is treated as a conversion from a garage to form a habitable space.

A garage conversion will be treated in the same way by Building standards as say building an extension or a loft conversion would, it will need to comply with building standards Scotland.

Below is a list of some of the main Building standards concerning Garage Conversions.

  • Insulation (walls, floor & roof need to achieve minimum standards)
  • Doors & Windows (generally double glazed to match the existing house)
  • Ventilation (Roof, walls & floor require adequate ventilation)
  • Structure (if new timber frame or new floor joists are required)
  • Fireproofing (particularly when partially converting a garage)

Design & layout

Careful consideration & planning needs to be given to your garage conversion project, you want to do the right thing and make it look great, you only get one chance, give thought to:

  • How it will look from the street (will it stick out like a sore thumb?)
  • Internal layout (you want to make the best use of space)
  • Integration with another room (can you create a large dining kitchen)


Walls, floors, and roofs need to meet minimum u values set out in current building standards.

U-values, measure how effective a material is an insulator. The lower the number the better the insulator.


The walls need to comply with building regulations, there are many options available to you to achieve this, this will be the designer’s job to include this in the building warrant drawings.

Both insulation (U values) and condensation risk are assessed.

Damp Proof Course (DPC) & Damp Proof Membrane (DPM) arrangements also need to be confirmed on the drawings.

You may wish to consider putting in more insulation than the minimum standards demand, this makes sense over the piece as it will help dramatically reduce heating costs, especially if the garage is detached from the house.

Foundations may require to be upgraded where doors have been, this will depend on what foundations are already in place.

Care needs to be taken to get the principal elevation to look right, French doors can be added where the garage door has been removed.

An incognito garage conversion can work well, this is where the existing garage door is left in place and an external grade wall is built behind the door, then a slapping (Hole in the wall) made at the other end with either French doors or Bi-fold doors, this way the external appearance of the house is unchanged,


The inclusion of insulation to the converted garage floor needs careful consideration. The chances of an existing concrete garage floor having insulation are practically nil, given that the existing garage floor will normally be lower than the house floor a joisted floor could be installed with insulation between the joists.

Alternatively, insulation and DPM may be laid on the existing floor and chipboard over the top, of course, each project will require a solution tailored to the individual project and more importantly tailored to you, the client!


Roof insulation is normally straightforward, if the garage has a trussed roof then glass wool insulation can be installed at ceiling level. A flat roof usually can have insulation in-between and above the joists.

Electrical & plumbing

Depending on the design of your garage conversion you may not require any plumbing works, however, care needs to be taken when creating door or window openings as existing pipework or electrics may be lurking behind the plasterboard, an experienced contractor will know this and will investigate before getting the sledgehammer out!

If, say you intend to add an en-suite then if possible try to make life easy for the builder by locating En-suites and bathrooms close to a water supply and soil pipes for foul water disposal

The electrical installation should be designed, constructed, installed and tested by a person or company having a membership to SELECT or NICEIC or similar Electrical schemes recognized by the Scottish Building Standards.

Doors & Windows

A fire door may be required between the garage conversion and the house, if the garage is an inner room (no direct access to outside) then an escape route will be required for compliance with building regs.

Windows that are compliant with building regs will have a clear unobstructed opening of 0.33m2 with neither height or width less than 450mm. Glazing to your garage conversion will need to have to an aggregate glazed area equal to 1\15th-floor area and an opening area of at least 1\30th of floor area.

Frequently the windows will be fitted with trickle vents to provided ventilation to the converted garage.

Both doors and windows are required to meet minimum U values as outlined in the table above.

Installation of doors and windows into the surrounding structure need to

be in accordance with BS8213-4 2007.


Adequate ventilation is required to protect the structure, if the floor is to be joisted then vent bricks are required to allow cross ventilation.

The roof space also requires minimum ventilation rates, your designer will be aware of these rates and include a note on your loft garage conversion building warrant drawings.

The wall cavity will also require ventilation if the garage construction is to be timber frame internally.

Again, this is something that your architect or designer will know and include in the garage conversion specification.


A Structural Engineer may be required, this will depend entirely on the extent of the structural alterations required for your garage conversion plans.

For example, if you intend to create large openings in the existing walls or are knocking down load-bearing walls then a structural engineer will be involved.

If you are looking to have a basic garage conversion done, then there is no need for a structural engineer.

Your architect or designer will still have to include details for how the floor joists will be fixed and any foundation alterations that need to be made to accommodate door infills.

Fire Resistance

Fire resistance in a garage conversion project may need Consideration to achieve the required fire duration (if any, this will differ from project to project)

For example, if you have a double garage and would like to convert half of this space to a bedroom, then fire separation would be required between the remaining garage and the rest of the house.

If you convert your single garage into a lounge with bi-fold doors that give direct access to the garden, then no fire separation would normally be required.

What a result! Stunning new family kitchen/dining area-post conversion

But How Much does a Garage Conversion Cost?

Find out in the next Blog Post or if you need an answer fast email me at john@jwarch.co.uk.


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