How much can i extend my garage without planning permission

Extending a garage is a popular way to gain extra storage, create a workshop area, widen a narrow entrance, or prepare a space for a future conversion. One of the first questions homeowners ask is how much can I extend my garage without planning permission. The answer depends on whether the garage is attached or detached, where it sits in relation to the house, whether permitted development rights apply to the property, and the size and height of the proposed extension. Although UK planning rules allow many garage extensions without a full planning application, there are strict limits which must be followed carefully.

This guide explains exactly how far you can extend a garage under permitted development, what the rules allow for different garage types, which restrictions apply to front facing extensions, what materials you must use, how height limits work, and when a full planning application becomes necessary. You will also learn how building regulations apply to garage extensions even when planning permission is not required. Real world examples help illustrate what is and is not permitted in typical UK homes including new builds, older properties, conservation areas, and detached garages in gardens.

By the end you will understand the full picture of how much you can extend your garage without planning permission and how to plan the project safely and legally.

Understanding permitted development rights for garage extensions

Permitted development rights allow homeowners to make certain changes to their property without planning permission. These rights apply to most houses in England although they do not apply to flats, maisonettes, or properties where rights have been removed through planning conditions or Article 4 Directions.

Garage extensions fall under the same general rules that apply to single storey rear or side extensions. This means that as long as the extension meets the dimensional and placement limits you can proceed without submitting a planning application.

How much you can extend an attached garage without planning permission

If your garage is attached to your house the extension is treated as an extension to the dwelling itself. The permitted development rules apply to the combined structure rather than the garage alone.

Single storey side extensions

You can extend an attached garage sideways without planning permission if:

• The extension is single storey
• The extension is no wider than half the width of the original house
• The height does not exceed four metres
• The extension does not extend beyond the front wall of the house
• Materials are similar in appearance to the existing house

This rule applies whether you are adding space to the side of the garage or extending the side wall of the property with the garage included.

Single storey rear extensions

If your attached garage is located at the rear of the house you can extend backwards without planning permission if:

• The extension does not extend more than three metres from the original rear wall of a semi detached or terraced property
• The extension does not extend more than four metres from the rear wall of a detached property
• The height does not exceed four metres
• It does not cover more than half the land around the original house

If your garage sits partly to the side and partly to the rear the rules depend on which elevation the extension affects.

How much you can extend a detached garage without planning permission

A detached garage has its own position within the rules which can be more flexible provided that the garage remains an outbuilding and does not form part of the house.

Detached garage extensions fall under the permitted development rules for outbuildings. This means you can extend or enlarge a detached garage without planning permission provided that:

• The garage remains single storey
• The maximum height is four metres with a dual pitched roof or three metres for any other roof type
• If within two metres of a boundary the maximum height is 2.5 metres
• The extension does not sit forward of the principal elevation of the house
• The extension does not create a structure that covers more than half the garden
• The garage is used for purposes incidental to the use of the house

Incidental use includes parking, storage, workshop activities, hobby rooms, or home gym use. It does not include creating a self contained living space such as a bedroom, bathroom, or annex which would require planning permission.

Can you extend a garage forward under permitted development

In almost all circumstances you cannot extend a garage forward under permitted development if it faces a road. Any extension that sits in front of the principal elevation of the property requires planning permission.

This means:

• Extending the garage towards the road at the front of the house always needs permission
• You cannot build a front projecting porch or storage extension onto the front of a garage without approval
• You cannot widen the garage towards the front unless the garage itself sits behind the principal elevation

If the garage is built behind the main front wall or is fully detached at the rear of the plot some frontward extension may be allowed as long as it is not forward of the house. This depends on the specific layout of your property.

Height limits for garage extensions under permitted development

The height rules are strict and must be understood clearly.

Attached garage extensions

An attached garage extension cannot exceed:

• Four metres in height for a single storey extension
• The height of the existing house if the garage forms part of the main structure

If the garage is attached to a two storey house the extension must remain single storey unless planning permission is obtained.

Detached garage extensions

A detached garage cannot exceed:

• Four metres in total height if using a dual pitched roof
• Three metres for a flat or monopitch roof
• 2.5 metres if the structure sits within two metres of any boundary

The boundary rule catches many homeowners out. If your garage is tight to the fence and you extend it you must keep the height below 2.5 metres without exception unless planning permission is obtained.

What materials must be used under permitted development

Permitted development requires that materials used on extensions match or are similar to the main house for attached garages. This rule is intended to maintain visual consistency and avoid irregular additions.

For detached garages materials do not need to match the house provided that the building remains incidental to the use of the property.

Matching materials does not require a perfect match but must be close in colour, texture, and overall appearance.

How far you can widen a garage without planning permission

You can widen an attached or detached garage under permitted development as long as:

• The extension is no wider than half the width of the original house if attached
• It does not exceed the outbuilding rules if detached
• It does not sit forward of the principal elevation
• It meets height limits
• It covers less than half the original garden

If the garage already occupies the maximum allowable width or if widening brings it close to the boundary you may need planning permission.

Real world UK examples

Example 1: Extending a side attached garage

A homeowner wants to widen their attached garage by two metres. The original house is eight metres wide. A side extension up to four metres wide is permitted. The proposal is only two metres wide which complies and can be done under permitted development.

Example 2: Extending a detached garage at the rear of the garden

A detached garage sits three metres from all boundaries. The homeowner wants to extend it by three metres to create a larger workshop. The new height will be three metres with a flat roof. This complies fully because it is within height and footprint limits.

Example 3: Extending a garage forward on a 1980s semi

The garage faces the road. The homeowner wants to build a two metre extension forward. This is not allowed under permitted development because it changes the front elevation. Planning permission is required.

Example 4: Increasing height on a boundary line

A garage sits directly against a boundary fence. The homeowner wants to raise the roof to 2.8 metres. This is not allowed because the structure is within two metres of the boundary. Height must remain below 2.5 metres unless planning permission is obtained.

Example 5: Garage on a new build estate with removed permitted development rights

The original planning consent states that the garage must be retained for parking. Any extension or alteration that reduces parking provision requires full planning permission regardless of size.

When planning permission is definitely required

• Any extension forward of the main house
• Any extension that creates a second storey
• Any garage enlargement that exceeds permitted height limits
• Any extension to a listed property
• Any garage conversion or extension creating habitable space
• Properties with Article 4 Directions
• Homes where the council removed permitted development rights

If you fall into any of these categories a full planning application is required.

Building regulations always apply

Even if planning permission is not required building regulations will apply to most garage extensions. Regulations ensure structural safety, insulation, drainage, fire protection, and electrical safety.

Building regulations apply if:

• You extend the garage footprint
• You alter its structure or roof
• You add electrical wiring
• You add insulation or heat the space
• You connect the garage to the house

A building control officer will inspect the work and issue a completion certificate which is important for future property sales.

Costs of extending a garage under permitted development

Costs vary depending on size, materials, and specification.

Typical UK costs include:

• Basic single storey extension: £1,500 to £2,000 per square metre
• Extending a single garage by two metres: £10,000 to £20,000 depending on roof type
• Extending a double garage: £15,000 to £30,000
• Adding a pitched roof: £5,000 to £12,000

Detached garages may be slightly cheaper because integration with the house is not required.

Mistakes homeowners often make

Assuming all garage extensions fall under permitted development

Many do but those facing roads or with height issues often do not.

Forgetting the boundary height rule

A detached garage within two metres of a boundary cannot exceed 2.5 metres in height.

Not checking whether the property has removed rights

Many new build estates have restrictions requiring a planning application even for small changes.

Extending a garage that was previously converted

A garage that is already partially converted may fall under different rules.

Ignoring drainage or rainwater management

Garage extensions must include proper guttering and surface water control.

Conclusion

So how much can you extend your garage without planning permission. In most cases you can extend a garage within the limits of permitted development as long as you stay within height restrictions, avoid building in front of the house, keep the width within half the width of the original dwelling for attached garages, and ensure the structure remains single storey. Detached garages can also be extended under outbuilding rules although height and boundary distances must be observed carefully. Planning permission becomes necessary when these limits are exceeded or when permitted development rights have been removed.

By understanding these rules clearly you can extend your garage confidently while avoiding costly planning delays and ensuring full compliance with UK building standards.