Last edited 13 Mar 2018

How to build a garage


A garage is a common type of single-storey extension that is constructed to adjoin an existing building, and can be useful for keeping a vehicle inside, storage space, and so on. The method of connection requires careful consideration, in particular, openings between the extension and the existing building, junctions with the roof structure, the positions of flues and drains, and so on.

A garage can also be constructed as an independent structure which is not adjoined to the main building, or it can be incorporated within the main building.

Building Regulations approval is required for building a garage but planning permission may not be in all instances – the local authority should be able to advise as to whether it is needed or not. As an outbuilding, a garage may be considered a permitted development which will not require planning permission as long as:

  • It is not forward of the wall forming the principal elevation.
  • It is single-storey with a maximum eaves height of 2.5 m, and maximum overall height of 4 m with a dual-pitched roof, or 3 m for any other roof.
  • It has a maximum height of 2.5 m within 2 m of a boundary.

The first stage of building a garage is to establish a plan or blueprint which lays out the dimensions and features in detail. An important consideration is where side access from the main building will be and whether a section of the existing wall will be able to be taken out to allow for the installation of a door.

It will be important, if the garage is to be used for storing a vehicle, that the correct size is ascertained, bearing in mind door opening radii. Typical sizes are 3.5 x 6 m for a single garage, and 6.5 x 6.5 m for a double garage (for two vehicles). The height of the door opening is also an important consideration.

Before beginning the foundation, the ground must be levelled as flat as possible and the firmness assessed. Hardcore can be used to firm up soft ground, as well as steel reinforcement used for the concrete slab.

Some of the topsoil should be removed, typically around 6 inches, so that the concrete slab will be level with the surrounding ground. A layer of firm tamped sand should be provided as support for the concrete which will be poured on top. It can be advisable to install a damp-proof membrane if the ground is prone to damp. It should be added to the whole base and also between the concrete and the adjacent wall to avoid damp transfer.

Structural rebar can be installed if required, and then the concrete poured and left to cure.

When the foundation has set the walls can be framed and then the roof built, typically using joists and rafters. Garage roofs are most commonly pitched or flat.

After this, the next stage is to build up the walls using either bricks or blockwork. The garage then needs to be wired with electricity and lighting provision, insulated, installed with drywall (if required), and then painted.

The final step is to install the garage door, which can be made of timber, steel or fibreglass. Many are fitted with a remote-control system which automatically raises and closes the door.

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