A complete guide to Garage Extensions: Everything you need to know.

Garage Extension Guide


  1. What are the benefits of a garage extension?
  2. Will a garage extension add value to my property?
  3. Do I need planning permission to build a garage extension?
  4. What type of garage extension should I build?
  5. What else should I consider for a garage extension?
  6. Do I need an architect for my garage extension?

A garage extension can be a fantastic way to add space and value to your home.

With house prices soaring, more and more people are seeking ways to maximize their current living space and find new storage. Garages are of course great for housing cars and bikes (a major plus in areas with limited parking!), but they’re also highly versatile spaces – with potential for home offices, playrooms or guest accommodation.

Whether you’re just thinking about a garage extension or already set-on a specific project, here’s a complete guide to garage extensions that includes everything you need to know to transform your garage.

1. What are the benefits of a garage extension?

There are so many good reasons for extending your garage. It’s a project that can have a massive impact on the way you use your home and outdoor space.

Here’s just a few benefits:

  • Space: It’s an obvious benefit but a big one. You’re creating extra space for your home. How you use it is up to you!
  • Value: Garage extensions often add significant value to your property, great news when you come to sell.
  • Parking: If you’re turning a one-car garage into two (or even three), this is a particular bonus in areas where parking is at a premium.
  • Cost: In terms of home-design projects, garage extensions tend to be cost-efficient. Whether luxury and bespoke, or simple and functional – you decide on your budget and goals.

2. Will a garage extension add value to my property?

Garage extensions increase the square footage of your home… and this often adds value.

As a rule of thumb.

Virgin Money estimates a 10-20% return on “well considered” garage extension projects that enhance the functionality and aesthetics of your home.


there are plenty of factors to consider. Not least how much you’re spending on the project. For instance, if you’re opting for beautiful, high-end exterior finishes and interior fittings, you run the risk of going over the “ceiling price” for your property.

Other factors impacting the value a garage extension brings include your location (i.e. city or rural), the complexity of your site, the quality of the build and materials used. In general, garage extensions with conversions (for instance, creating an office, bedroom or playroom) typically add the most value.

None of this is set in stone though. So if potential profit is important to you, chat to your architectural team about maximizing value. They’ll be able to advise on the best designs for your needs.

3. Do I need planning permission to build a garage extension?

The short answer is, sometimes.

You’ll probably need planning permission to build your garage extension, but there are certain projects allowed under permitted development rights. Depending on the location of the project and proximity to neighbours, you might also need a party wall agreement.

The most common route for a garage extension is a full planning application. Alternatively, you can apply for a “lawful development certificate” if you’re using permitted development rights. This mainly covers rear or side garage extensions. If you’re adding a second storey or live in a listed building or a conservation area however – you’ll need prior permission.

If you’re in doubt at any point, contact your local council’s planning department. It pays to get the legal documents right from the start, to avoid any stressful situations further down the line.

4. What type of garage extension should I build?

There are so many options when building a garage extension – and costs can range anywhere from £5,000 to £25,000 and up.

For instance.

Do you want to go single or double storey? Brick, concrete blocks or wood? Where do you want to place the extension and how will this impact your existing home and garden? Each choice has cost implications too, so it pays to do your research at an early stage.

To help your decision, here’s a few considerations:

Single vs Double Storey

Single storey garage extensions are often more straightforward and more likely to fall within permitted development rights. They do eat-up more garden space however (which can sometimes have a negative impact on your property’s value), so think carefully about what you want for your home.

Double storey extensions are often better if you’re hoping to combine a conversion (and extra living space) with a “standard” garage extension project. As well as single or double storey, expect to pay more for a double-width garage than a single-car garage. As a rule of thumb, the greater the square footage, the greater the price.

Flat vs Pitched Roof

The two common types of roof are pitched roofs (matching the angle of your home) and a flat roof. Flat roofs tend to be much simpler and cheaper, making it an ideal choice if you’re thinking about a second storey in the future. Nonetheless, pitched roofs are often better for adding value to your property, and have less issues with leaks and weak points.

Detached vs Attached

A detached garage is classed as an outbuilding, and if you’re planning to use it for extra bedroom space (or adding a bathroom), planning permission will be required. This will also come with extra costs for getting wiring and electricity across (as opposed to a structure attached to your home).

If you’re opting for an attached structure, consider how it will impact the look and flow of your current home. Whilst this may come with costs in terms of higher-quality finishes, windows and doors, you might save money when connecting utilities due to the reduced distance.

Building Materials

A single-storey, prefabricated concrete garage is one of the most cost-effective options available. Prefab garages are quickest and cheapest to build, but offer less security, longevity and flexibility in design.

Prices increase if you opt for metal or wood constructions. If you own a period home, wood-framed designs can be great for creating an in-keeping structure. They are more prone to mould and deformation though, requiring ongoing maintenance and care.

A traditional brick garage is one of the most expensive options, but also the most common and versatile construction method that’s most likely to add value to your home. You could also opt for a garage made from concrete blocks (as opposed to bricks) which are cheaper, but offer less design choice.

Checkatrade has a rough guide to costs for garage extensions, great for initial ideas before chatting with your architectural team about plans and budget.

5. What else should I consider for a garage extension?

First and foremost, think about how you plan to use the space. For instance, do you want to add external access to your home? Will you need electrical installation and plumbing for water and drainage? These considerations will significantly impact the cost and complexity of the project.

If you’re planning a change of use alongside the extension, will you need to find alternative spots to store white goods, bikes or all those pots of paint and varnish?

Whilst garage extensions can be relatively straightforward, don’t forget early steps like surveyors visits to create drawings of your current space. These will form the foundation of your garage extension project – used by architects, builders and planners alike.

6. Do I need an architect for my garage extension?

If you’re undertaking a very simple prefab project, you could work with a company specialising in design-build garage extensions. If you’re planning anything more complex however, the services of a professional architect are advisable.

They’ll identify creative ways of maximizing the potential of your garage space, and help you create a usable room that flows naturally and beautifully into your existing home. Aside from the design itself, an architect’s hands-on experience can help your project run smoothly, assisting with planning, budgeting and building regs approval, as well as working with contractors.

Thank you for reading our garage extension guide.

If you’re getting started with a garage extension, get in touch with our expert team at EV Architects. We’ll help you through every step of the process and create a fantastic space that works for you and your home.