Garage Extension Costs: 2023 Prices (UK Guide)

Garages are one of those property essentials that you already own or wish you owned. In the UK, we use them for storing vehicles, bicycles and almost anything you can think of. However, often their size is too small to be useful for anything except storage. Then, it’s time to spend some money to extend your garage into somewhere more useful. But what is the cost of a garage extension?

A single prefabricated garage can cost, on average, £2,000-£13,000, depending on the material and roof type. In contrast, a tradesman-built brick garage can reach £20,000.

This guide will explain why you might extend your garage, the construction costs, the factors that affect these costs, and the regulations you must follow.

Garage Extension Cost Breakdown*

In the UK, architects use standard measurements for an ideal garage when designing a new house. These are 3m wide x 6m long for a single garage and 6m wide x 6m long for a double garage. However, older houses have garages built to accommodate the size of vehicles prevalent when they were built, often too small for today’s needs. However, practicality always wins over standardisation. So, you can buy plans online for many standard sizes other than the “ideal garage” or choose a unique design using an architect. 

The table lists the estimated costs of building a single garage, with an area of approximately 16m2 and a flat roof. Double garages cost about 75% more than singles.

Type of ExtensionCost + VAT (Range low - high)Average Cost
Concrete Prefabricated Garage£3,000-£7,500£5,250
Metal Prefabricated Garage£2,500-£7,000£4,750
Wooden Prefabricated Garage£2,000-£6,500£4,250
Brick Garage (incl. Floor Slab, Walls, Roof, Door)£13,500-£20,500£17,000
Pitched Roof (Single Garage)£2,500-£6,500£4,500

*We compiled these estimated garage extension prices from various resources for four popular garage materials. However, prices have increased significantly over the past few years and show no signs of levelling out. Therefore, always ask qualified and experienced tradespeople for the most recent and accurate estimates using the form on this page.

Brick garage extension costs 

Brick garages are the most popular in the UK but are also the most expensive. However, they last many years and are much higher quality than a standard kit-based alternative. Also, you can design and build them to suit your exact requirements. Brick-built extensions cost from £13,500-£20,500 depending on several factors.

Concrete prefabricated garage cost

Concrete prefabricated garages come as a kit and need pre-existing concrete foundations. The walls arrive as a series of concrete panels which are easily bolted together. However, a professional with mechanical handling devices, who knows what they’re doing, must handle the heavy panels. Although prefab garages don’t look as good as brick-built and are limited to a standard shape, they are much more affordable and take much less time to install. Generally, concrete prefabricated garage kits cost £3,000-£7,500, depending on various factors.

See also  Woodworm Treatment Cost: 2023 UK Price Comparison

Metal garage extension cost

Metal prefabricated garage kits also come as a series of panels. They’re cheaper than concrete garage kits and are easier to install. But, you should still use a professional. However, they are less secure and not as sturdy as a concrete kit. So, only use them as a temporary structure. Typically, prices range from £2,500-£6,500.

Wooden garage extension cost 

Wooden prefabricated garage kits are the cheapest but are also the least secure. Generally, expect them to last for only a few years, as they are liable to rot, split, and deform. However, if maintained and installed correctly, wooden garage kits can last several years. Depending on your garage’s purpose, the cost of increased maintenance and lower security might not be suitable, even if it’s cheaper than other types. Once again, install a concrete foundation before erecting the kit. Typically, a wooden garage kit costs £2,000-£6,500, depending on several factors.

10 Garage Extension Price Factors

Extending a garage is a complex job and one that you should leave to a professional. The additional walls and roof must be seamlessly attached to the existing garage to prevent weather ingress, thus preventing dampness in the building’s structure. 

Here are several factors that affect the above prices.

1. Size of Garage

The prices given above are for a 16m2 garage. You would expect a smaller structure to cost less but have a slightly higher cost per square metre. Similarly, a larger garage would cost more but would have a lower price per square metre. Ask for a professional estimate based on your requirements before deciding.

2. Garage Door Specification

Garage doors cost from £750 for a standard up-and-over door and from £850 for a roller door. Furthermore, automatic doors start at about £1,300 but can reach £3,000 or more for a high-end electric version.

You’ll also find that the garage door’s type, material, size and colour also affect the cost.

3. Insulation

Most single-storey garage extensions are just for storage. But, if you intend to use it as a hobby room or a children’s play area, consider thermally insulating the space to make it usable in the winter. Furthermore, suppose you intend to build a double storey garage extension to include a liveable area, perhaps an upstairs flat. In that case, Approved Document L of the building regulations state that you must add the legally required minimum insulation thickness and comply with other rules before the space is habitable.

To fully insulate a habitable part of a garage extension costs up to £1,000.

4. Wall & Ceiling Finishes

Most garages have single-skin walls and exposed roof rafters instead of finished walls and ceilings. Usually, this is enough to protect against the weather. However, if the space is to be habitable or used for any reason except storage, it should have finished walls and ceilings. Plasterers charge £150-£250/day, and decorators charge £180-£280/day. Typically, the cost to install plasterboard and paint will be an extra £40-£50/m2.

5. Location

The cost of living in the UK varies with region. The prices stated in this guide apply to Southern England, which can be up to 20% higher than prices in other areas of the country. Contact a local contractor using the form on this page to get a quotation relevant to your area.

6. Existing structure removal

Often, existing garages can be in disrepair and require demolition. If so, allocate additional funds for this, including hiring a waste skip. Demolition costs depend on the person you hire. But, more importantly, if the existing garage has a corrugated asbestos roof, you must employ a specialist contractor to remove and dispose of the asbestos safely. This will increase the cost of the work. 

See also  Bifold Doors Cost: 2023 Fitting & Installation Prices UK

7. Concrete base

All existing garages have some kind of foundation. But, it probably isn’t suitable for the new garage extension, especially if it has two-storeys. In this case, removal of the existing concrete, tree roots, and other obstructions followed by preparation and construction of new concrete foundations and floor can significantly add to the cost.

8. Flooring, windows and doors

Using a garage as a storage area doesn’t need these additions. But, to make the space enjoyable to use, add insulated flooring, double-glazed windows, and a personnel door. However, these additions will increase the overall cost. Typically, uPVC door and window fitters charge £150-£200/day.

9. Connecting utilities

Many people use garage extensions as a utility room, bathroom or kitchen. But, adding heating, water, drainage, gas and electricity supplies increase the overall cost. Typically, plumbers charge £240-£300/day, kitchen fitters charge £180-£250/day, and electricians charge £240-£300/day.

10. Design

If you aren’t using a prefabricated kit, you will need drawings to guide the builder and structural calculations for the building control department. Furthermore, you must apply for planning permission with an architect’s drawings if your project doesn’t come under the Permitted Development Rights. Generally, architects charge from 5% to 12% of the total project cost, and structural engineers charge £150-£250/hour.

Garage Roof Types

You can use one of two basic roof types when building a garage extension. 

Pitched roof

This roof has a slope (or pitch) that will usually be the same as the pitch of the main house roof. A typical pitched roof costs £2,500-£6,500 depending on size, complexity and materials. Adding a complex roof adds up to 14 days to your project.

Flat roof

A flat roof is a much simpler and cheaper option to choose. Contrary to what you might expect, a flat roof isn’t horizontal. All roofs need drainage, so a flat roof must have a slope of at least 1:80, as specified in Approved Document H of the building regulations.

How Long Does The Job Take?

Typically, a single or double prefabricated garage takes approximately the same time because the kits come as quickly erected panels. However, a single tradesman-built brick garage takes around 10-14 days, while a double garage with a pitched roof can take up to 1 month. 

Single Prefabricated KitConcrete Garage with Corrugated Roof5 days
Metal Garage with Corrugated Roof3 days
Wooden Garage with Corrugated Roof3 days
Single Brick-BuiltGarage with Flat Roof10 days
Garage with Pitched Roof14 days
Double Brick-BuiltGarage with Flat Roof14 days
Garage with Pitched Roof30 days max.

Benefits of Extending Your Garage

A few benefits might convince you if you’re considering extending your garage.

Space for vehicles

A large garage will always give you enough space to park your vehicle, irrespective of the vehicle’s size. And if your family has more than one car, extend the garage to accommodate all of them.

If you have a boat, motorhome, jet skis, bicycles, motorcycle or another non-standard vehicle, build a garage large enough to protect these as well. A garage will allow room to protect them from the weather, vandalism, theft, and you can maintain them while protected from the weather.

Electric vehicle charging

If you have an electric vehicle, there’s often a problem with charging it overnight. Installing a charger in an extended garage allows you to plug in your car without worrying about vandalism or the equipment getting wet.

Storage space

Most people need more storage space than they already have. Extended garages easily have enough space for all your vehicles and room for storage.

See also  Double Glazing Cost: 2023 Window Price Comparison UK

Hobby room

Many people have hobbies that need plenty of space, for example, artists, potters, and DIY. You can easily incorporate space for these and more in your extended garage.

Potting shed

If you enjoy working on your garden but don’t have enough room for a shed, you can use part of your garage as a potting shed and storage for garden tools.

Home gym

Running and rowing machines, and weights take up a lot of room in your house that you can use for other purposes. Moving your home gym into an extended garage keeps them away from the house, and the noise won’t disturb the rest of the family.


If you have boisterous and messy children, it’s an excellent idea to give them enough space in an extended garage where they can bring their friends and play games without disturbing the adults in your home. But, remember that you shouldn’t leave small children unsupervised. 

Increase your home’s value

Many homes in the UK don’t have garages. Therefore, a garage, whether extended or not, will always be a way to increase your property’s value.

Extension Planning Permission & Regulation

Planning permission

Before starting your project, do some research to find out the rules and regulations you must comply with. Usually, a garage extension comes under the category of Permitted Development, and you won’t need to apply for planning permission. But, if you intend to change the shape or design of your existing house, significantly increase the garage’s area, raise the height of the existing garage roof, or add balconies, you should contact your local planning department for confirmation. Furthermore, you will also need permission if you live in a conservation area, your house is listed, or you intend to convert the garage into a separate dwelling. 

Building regulations

Building regulations apply to an extended garage if all or part:

  • Is a habitable space
  • Has electricity, water or drainage installations
  • Is attached to your house

Once again, contact your local council for advice if you are unsure.

Protected species

Many old garages are home to wildlife, such as protected birds and bats. If this applies to your garage, you must have a protected species survey done at the planning stage before submission to the local council. If the survey finds protected species, the council will instruct you to postpone the project or refuse it entirely. See this Planning Portal webpage for more details.

Party Wall Act

The Party Wall Act protects your neighbours’ property from damage caused by work done on your property. Typically, this legislation applies to garden boundaries and the structural integrity of foundations, walls and roofs of semidetached and terraced houses. If you’re unsure if your project comes under this legislation, contact the local council for advice, as ignoring the applicable legislation can lead to severe repercussions.


Building an extension onto your existing garage can provide much-needed space for your family and their belongings. But, you must build the extension according to current construction methods and, if applicable, the building regulations and other UK legislation. You can do this easily by buying a prefabricated garage kit or having one built from scratch using a qualified building contractor. Whichever you choose, make sure the installer is a registered competent person.

Complete the form on this page, and you’ll receive up to four garage extension quotes from qualified local contractors.

Leave a comment