What's the Cost of an Extension Over a Garage in 2023? | Checkatrade
Review a Trade

Have you completed a project recently? Let your tradesperson know how they did.

Advice Centre

Get Inspired! Check the latest industry expertise and read insider tips from our vetted tradespeople.

Search For A Trade

We interview and vet all our tradespeople to ensure they meet our high standards.

Join Checkatrade

Join us and benefit from the millions of potential customers who use Checkatrade to find reliable tradespeople.

Advice Centre

Grow your business! Check out top tips and expert advice for boosting your reputation online.

Login To Your Account

Edit your profile, view callback requests and ask for feedback from customers.

Last updated on April 3rd, 2023

How much does an extension over a garage cost?

In need of some extra living space? Building an extension over the garage could be the perfect solution, allowing you to create an extra bedroom or an ensuite bathroom.
The Checkatrade guarantee
The Checkatrade guarantee

When you book a job with Checkatrade, our guarantee covers you for up to 12 months. You can claim up to £1,000. Exclusions and T&Cs apply.

By adding to an existing structure, you’ll be able to make use of otherwise wasted space and avoid eating into your garden. A new pitched roof can often eliminate any water ingress issues that old flat roof garages suffer with, so you can kill two birds with one stone.

Here, we’ll look at the typical cost of an extension over the garage. It can often work out cheaper than building a new extension from scratch, as the groundworks and foundations are already built.

Cost of extension above single garage

An extension over a single garage won’t give you heaps of extra space, but it could still be very useful. For example, you could create a new child’s bedroom or playroom, home office or an ensuite bathroom.

Extension typeLow costHigh costAverage cost
Extension over garage£20,000£35,000£27,500
Extension with ensuite bedroom£23,500£38,000£30,750

Our costs are ballpark averages – get a local tradesperson to quote now

It could cost around £20,000 to build an extension over a single garage, including the roof.

See the tradespeople we've checked and recommend for your job

How much would an extension over a double garage cost?

An extension over a double garage gives you lots more space, enough for a new master bedroom or family bathroom.

It can cost around 30% more than an extension over a single garage, and you could pay up to £35,000 for a completed project. Structural issues may complicate matters. If the garage requires underpinning, this can increase the cost considerably. Likewise, if you need to relocate walls or retile for a bathroom where another room was before.

Cost of extension above garage with ensuite bedroom

If you’d like to create a new bedroom with an ensuite bathroom in your new above-garage extension, you’ll find the ensuite to be the most expensive part. Once the extension is built, fitting a bathroom could cost around £5,000.

Extending over a double garage is recommended to give you enough space. But if you only have a single garage, you can still create a new ensuite for an existing bedroom. This means in total, your extension with an ensuite bathroom will cost between £23,500 and £38,000.

One thing worth noting in advance is that garage roof extensions can really highlight how worn out and tired your main house roof is looking. Consider asking your builder for an optional price to re-tile/slate the whole main roof to see if your budget would allow for this work.

Plumber fitting en suite shower

See the tradespeople we've checked and recommend for your job


Can I build an extension over a detached garage?

You can certainly build an extension over a detached garage, this could create an ideal space for a home office or guest room. You might even find it less complicated a project, as the rest of your home won’t be affected by building work. But you need to allow for access, for example, a staircase in the garage into loft space, or otherwise an external staircase. Also, many garages, including detached ones in particular, have inadequate foundations to support an increased amount of brickwork and would need structural surveys and potentially work in the foundations to allow the additional building work to take place.

Will an over-garage extension upset my neighbours?

It’s a good idea to seek advice from your local planning department on how your extension will affect neighbouring properties. There are certain things you may need to do. For example, leaving a gap between your extension and next door’s upstairs avoids what is known as ‘terracing’. You should also avoid blocking your neighbour’s windows or other key fixtures where possible.

You might also want to speak to affected neighbours in advance, to let them know your plans and provide some reassurance.

Do I need planning permission to extend over my garage?

Depending on the size of your extension and other details of your plans, you may not need planning permission. Your extension may fall under what is known as ‘permitted development‘. However, it’s recommended to speak to your local planning department for guidance.


Blue tick
The tick you can trust

8/10 homeowners would choose a tradesperson endorsed by Checkatrade over one who isn't*

Claims are sourced from a survey conducted by Deep Blue Thinking on a nationally representative UK sample in November 2021. *8 out of 10 people would choose a trade endorsed by Checkatrade compared to one that isn’t endorsed.

Tell us what you think

Please leave your comment

Your email address will not be published. Required fields are marked *

What others think of this article:


Hi Edi, to get an estimate, I recommend using our free request a quote feature to get quotes from trades near you.


Hi, what would be an estimated cost of above double garage extension for bedroom with en-suite bathroom. The garage is detached with approximately one meter wide passage way from the house. The house is built in 1980-1990. Thank you

Also in this project

How much does it cost to build a double storey extension?

Drastically improve your living space, with our in-depth guide to reducing the duration and cost of a two story extension. With useful tips and factors to consider....

Read more
How much does a bungalow extension cost?

Unlock the potential of your bungalow with our helpful bungalow extension cost guide. From loft to rear extensions with pricing, considerations and conclusions....

Read more
How much does a garage conversion cost in 2023?

Unlock the value of your most underused room with our complete guide on converting a garage. Including how to do it, garage conversion prices and handy tips....

Read more
Interior designer cost and charges guide

Hiring an interior designer can often be overlooked when people are renovating their homes because of the potential expense. But the benefits of using an interior designer often outweigh the cost....

Read more