Do I need planning permission for a garage extension?

Often, no — adding a garage to your property doesn't need planning permission if the project falls within permitted development. For a garage built as an outbuilding, that broadly means single storey, no more than 4 metres high with eaves at 2.5 metres, and not covering more than half the land around the original house. Check the details with your local authority before you build.

Permitted development rights are a national set of permissions, granted by Parliament rather than your local council, that let homeowners carry out many common projects without applying for planning permission. Garages and other outbuildings are among the classic examples — which is why most prefab concrete garages go up without a planning application.

The rights come with conditions, though, and it's the conditions that decide whether your particular project qualifies.

Houses generally are; flats, maisonettes and commercial properties are not — they don't have these rights, so a planning application is needed from the start. Location matters too: in a national park or conservation area, permitted development is restricted and projects that would sail through elsewhere may need consent.

Some houses also have their permitted development rights removed by planning conditions, so if you're unsure, ask your local planning authority — it's a quick check that can save an expensive mistake.

For garages and other outbuilding projects, the headline limits are:

• Single storey only, with a maximum height of 4 metres and eaves no higher than 2.5 metres. • Outbuildings must not cover more than 50% of the land around the original house — 'original' meaning the house as first built, or as it stood on 1 July 1948. • No raised platforms or balconies.

Prefab concrete garages are designed with these limits in mind, which is one reason they so rarely need a planning application. If you're extending an existing attached garage rather than adding a freestanding one, different extension rules apply — your local authority can confirm which set covers your project.

You can simply apply for planning permission — falling outside permitted development doesn't mean the answer is no, only that the council gets a say. Applications go through your local planning authority, and for borderline cases a Lawful Development Certificate is a cheap way to get certainty in writing.

We've supplied around 1,100 buildings a year for decades, so whatever your site looks like, we've almost certainly dealt with one like it — ask us and we'll tell you straight whether yours is likely to need permission.