How big can a garage be without planning permission UK

One of the most common questions homeowners ask when planning a new garage is how large the structure can be before planning permission becomes necessary. UK planning rules can appear complicated because they depend on several factors including the height of the garage, its distance from boundaries, its overall footprint, and where it sits in relation to the main house. Many garages can be built under permitted development which allows homeowners to construct certain outbuildings without a full planning application. However permitted development is not unlimited and exceeding the rules can result in costly planning problems.

This guide explains exactly how big a garage can be without planning permission in the UK. It breaks down the permitted development rules in simple terms, covers height limits, footprint restrictions, boundary limitations, and real world scenarios that help homeowners understand how the rules apply to their property. It also highlights exceptions, common misunderstandings, and when planning permission is unavoidable. By the end you will know exactly how large your garage can be and how to design it confidently within the legal limits.

Understanding permitted development for garages

Permitted development is a set of national rules that allow homeowners to build certain types of extensions and outbuildings without needing a planning application. Garages are classed as outbuildings along with sheds, workshops, and garden rooms. If your proposed garage meets all permitted development criteria you can build it without planning permission.

However failing just one of the criteria means permitted development no longer applies and planning permission is required. Size plays a major role in determining whether a garage is permitted development. To understand the maximum size you must consider height, footprint, and position.

Who needs to understand garage size limits

Homeowners building a new garage
People replacing a small garage with a significantly larger structure
Homeowners adding a detached garage to the side or rear of the property
Builders and tradespeople designing garages for clients
Landlords upgrading investment properties
Anyone on a corner plot where planning officer interpretation can differ
Homeowners in conservation areas or new build estates where restrictions are tighter

Knowing the correct size limits helps avoid planning refusals, enforcement action, and wasted construction costs.

The maximum size a garage can be under permitted development

To determine how big a garage can be without planning permission you must meet all the following permitted development rules.

1. The garage must not cover more than 50 percent of the land around the original house

This is the most important rule affecting footprint. The land around the original house includes all space within the property boundary excluding the area occupied by the house as originally built. If the garage plus all other outbuildings cover more than half of this land planning permission is required.

This rule sets the functional limit on how large the footprint of a garage can be. You do not need to measure the entire garden precisely but you must ensure the garage will not occupy more than half of the remaining garden space.

2. The garage must be single storey

A garage with two storeys always requires planning permission regardless of footprint.

3. Maximum height limits apply depending on roof type

Permitted development sets strict height limits:

Dual pitched roof (gable or hipped): maximum overall height of 4 metres
Flat roof or single pitched roof: maximum overall height of 3 metres
Eaves height: maximum of 2.5 metres

Even if your garage occupies a small footprint it loses permitted development rights if it exceeds these height limits.

4. If the garage is within two metres of a boundary the maximum height is 2.5 metres

This rule catches many homeowners off guard. If you place the garage close to a boundary fence or wall the entire structure must be no taller than 2.5 metres. This restricts most pitched roof garages because they usually exceed this height.

If you want a pitched roof garage larger than 2.5 metres high you must place it more than two metres from the boundary.

5. The garage cannot be built forward of the principal elevation

A garage built in the front garden or anywhere in front of the main front wall of the house always requires planning permission regardless of size.

6. The garage must be for domestic use

A garage used for storage, parking, or a hobby is permitted development. A garage used as a separate living space or commercial premises can require planning permission because it changes the use of the building.

How large the footprint of a garage can be without planning permission

Permitted development does not set a specific maximum footprint in square metres. Instead it uses the 50 percent garden coverage rule. This means the maximum size varies depending on the size of your plot.

Example 1: Large detached property

A home with a substantial garden could build a very large garage without planning permission as long as it covers less than half the remaining land and meets height restrictions. This could mean a garage of 40 to 60 square metres or more.

Example 2: Typical suburban semi

A typical garden may allow a garage footprint of around 15 to 25 square metres while remaining within permitted development limits.

Example 3: Compact modern estate home

A smaller plot may have very limited space. A garage may need to be around 10 to 15 square metres to stay under the 50 percent limit.

The footprint rule focuses on proportional size rather than specific measurements.

Height restrictions and how they limit the size of a garage

Even if the footprint meets permitted development rules the height can still restrict the size of the garage. For example:

A large pitched roof garage more than 2.5 metres tall placed near a boundary loses permitted development rights.
A tall garage designed for vans or high vehicles may require planning permission even with a small footprint.
A flat roof garage is limited to 3 metres which may restrict headroom for certain uses.

Height is often the deciding factor that triggers planning permission in real world situations.

Real world UK scenarios showing how big a garage can be

Scenario 1: A large double garage at the rear

A detached property has a large rear garden. The homeowner can build a 6 metre by 6 metre garage with a pitched roof 4 metres tall as long as it is more than two metres from all boundaries. This falls within permitted development.

Scenario 2: Wide single garage near a boundary

A homeowner wants a 5 metre wide garage next to a boundary fence. To be permitted development the garage must not exceed 2.5 metres in height. This usually results in a flat roof design.

Scenario 3: Side garage on a semi detached home

A pitched roof garage 4 metres high is planned at the side. The boundary is only 1.5 metres away so planning permission is required because of the 2.5 metre height limit near boundaries.

Scenario 4: Large garage on a small garden

The homeowner wants a 20 square metre garage but the garden is small and already contains a shed. Combined outbuilding coverage exceeds 50 percent of the garden. Planning permission is required.

Scenario 5: Garage in the front garden

A garage of any size positioned in front of the house needs planning permission even if it is small.

Exceptions where permitted development does not apply

Even if your garage meets the size rules permitted development may still not apply in these locations:

Conservation areas
Areas of outstanding natural beauty
World heritage sites
National parks
Broads
Listed buildings
Some modern housing estates with restrictive covenants
Properties with previous planning restrictions removing permitted development rights

In these cases a planning application is often required for any garage regardless of size.

How roof design affects the maximum garage size

Garage height limits depend on roof shape which can affect practical size.

Pitched roof

Allows up to 4 metres total height but must be away from boundaries.
Good for storage space in the roof void.

Flat roof

Maximum 3 metres in height.
Can be placed near boundaries but sacrifices headroom and appearance.

Pent roof (single pitch)

Maximum 3 metres.
Often used for garages near fences because height is restricted.

Choosing the right roof shape can expand or restrict the size of garage you can build without planning permission.

Impact of the boundary rule on garage size

The boundary rule is often the biggest limiting factor. If the garage is within two metres of a boundary the height must be 2.5 metres or less. This significantly restricts how big the garage can be vertically. Pitched roofs usually need more height and therefore must be positioned further away from the boundary.

Many UK suburban plots only have narrow gaps between houses and boundaries which often triggers the need for planning permission.

Garage use and why size matters

The size of the garage can determine whether planning officers consider the structure incidental to the house.

A standard vehicle garage used for typical domestic storage is usually permitted development.
A very large garage with office space, gym facilities, or utility rooms may be seen as an outbuilding beyond incidental use.
A huge garage that dwarfs the house may raise planning concerns.

Even permitted development structures must remain proportionate to the main dwelling.

Building regulations and garage size

Even if planning permission is not required you may still need building regulation approval depending on size and design.

Detached garages under 30 square metres built from non combustible materials often do not require approval.
Attached garages need approval because they form part of the main structure.
If the garage includes electrics, plumbing, or insulation building regulations may apply.

Larger garages are more likely to fall under building regulation requirements even if they do not need planning permission.

Common mistakes when assessing garage size limits

Assuming small footprint equals no planning permission
Position and height are just as important.

Building near a boundary without checking height limits
Many pitched roof garages lose permitted development rights this way.

Assuming permitted development always applies
Some properties have restricted rights.

Believing that using lightweight materials avoids planning permission
Planning rules apply regardless of material choice.

Copying a neighbour’s garage size
Neighbours may have had planning permission or different site constraints.

Tips for maximising garage size without planning permission

Place the garage more than two metres from boundaries to allow full height
Use a pitched roof to gain headroom and storage
Choose a location to the rear to avoid front elevation restrictions
Limit total outbuilding coverage to well under 50 percent of the garden
Design the garage to complement the property so it remains incidental
Use internal layout planning to maximise usable space

Careful planning allows homeowners to build surprisingly large garages without requiring permission.

When planning permission becomes the best option

Sometimes applying for planning permission is more practical than designing within permitted development limits. This may be the case when:

You need a tall garage for a van or 4x4
You want a double garage with generous roof height
Your boundaries are too close to allow a standard design
You want additional workshop space or storage
You live in a restricted area
You want the garage built at the front of the property

Planning permission allows more freedom in size and design and can improve the final result.

Final thoughts

The maximum size a garage can be without planning permission in the UK depends on several permitted development rules rather than a fixed measurement. The garage must not cover more than half the garden, must be single storey, must stay within strict height limits, and must not sit forward of the main house. The most restrictive factor is the 2.5 metre height limit within two metres of a boundary which often limits how large the structure can be. Understanding these rules helps you design a garage that fits your plot, avoids planning issues, and meets your needs. With careful planning many homeowners can build a sizable garage under permitted development while others may choose planning permission to achieve the exact space they want.