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By Amy Hanlon on 02 Apr 2024

What’s the biggest garage you can build without planning permission?


You’re not just thinking about a big garage. You’re looking for the biggest garage you can build. But what about planning permission? Won’t that be expensive, difficult, and hold up your project?

Not necessarily. Let’s look at how permitted development rules mean that in many cases, planning permission isn’t needed even for large garages.

What is permitted development?

Permitted development rules exist to let people avoid planning permission for certain types of building projects. Garden buildings like garages often fall under this category. In fact, the majority of the buildings that we install don’t need planning permission as a result.

In the rules for permitted development, garages are referred to as ancillary buildings. This term also covers sheds, garden rooms and other similar structures. Because you’re not going to live in these buildings, they are ancillary to your main home. Very often, these buildings don’t need planning permission. 

But it will depend on your circumstances. To help, we’ve created a planning permission checklist to help you navigate the permitted development rules.

How to use the Planning Checklist:

Each question on our Planning checklist refers to the rules for permitted development. As a general guide, if you can answer NO to all of these questions, you’re unlikely to need planning permission.

Remember that the questions on the checklist are intended as guidelines. The best way to be sure about whether or not you’ll need planning permission is to consult your garage company.

They should be able to advise you, and may even offer an application service if planning permission is needed.

Let’s quickly run through these questions:

Is your building going to be used for business?

Permitted development rules apply to what the government calls “dwellinghouses”. This Middle Earth-sounding term just means that the building is a home that someone lives in.

If you’re building a garage specifically for business use, even in your back garden, permitted development rules don’t apply. In this case, you’ll need planning permission. 

Do you live in a tenement block?

If you live in a shared building, the assumption is that the area behind your house is also shared. This means you can’t just plonk a garage there and hope that the other people who share the garden will be ok with it. 

If the ground is all yours, there’s no issue.

Do you have upstairs and downstairs neighbours?

This is the same principle as the previous question. A shared building means that even if the garden is yours, your plans may impact your neighbours. If you don’t have upstairs or downstairs neighbours, you don’t have to worry about this.

Is the building outside your garden?

The area around your home is officially referred to as the curtilage. This term means all the land that belongs to your property. Curtilage includes your garden, paths, patios or any other piece of land that isn’t shared with anyone else. 

Since the curtilage comes with the house, it’s yours, and you can build ancillary buildings on this land. If it’s not your land, you can’t build on it. 

Is the building in front of your home?

Permitted development rules apply to buildings that won’t be visible at the front of your property. This is to prevent any changes that would affect the appearance of your street. These sorts of changes might impact your neighbours and the overall area. If a garage is going behind your house, it won’t bother anyone.

Is the building within 1m of a boundary?

It’s absolutely possible to build within 1m of a boundary, but if you do, the rule states that the building can’t be more than 2.5m high. However, what this rule actually means is that no part of the building that is within 1m of the boundary can be over this height. Take a look at this diagram:

A diagram showing a boundary and a 1m by 2.5m box. A shed or summerhouse outline is shown, part of which is inside the box, showing that planning permission isn

This slightly confusing rule doesn’t mean that the building has to be under 2.5m in height. As long as your building isn’t higher than this imaginary box, you can answer no to this question.

Is the building more than 4m tall?

It is highly unlikely that a single-storey garage would ever be taller than 4m. That would be one extremely tall garage. Unless you’re storing farm machinery or secretly housing a dinosaur, you won’t need a garage to be this height.

Does your building have walls more than 3m high?

This measurement applies to the point where the walls and the roof meet. As with the overall height restriction, it’s highly unlikely that a garage would need walls higher than 3m.

Do you live in a listed building or conservation area?

Here’s where things get a little more complicated. There are over 600 conservation areas in Scotland, and people don’t always know whether or not their homes are in one of these zones. 

If you’re unsure, have a look at your local authority’s website. This will have maps of any conservation areas within the council.

Living in a conservation area doesn’t necessarily mean that you can’t have a garage. But it will mean that you’ll need planning permission for the building. 

The same rules apply if your property is a listed building. This doesn’t rule out the possibility of a garage, especially a timber garage. But there will be more admin and costs involved because your local authority will have to approve any changes. 

Is the building more than 50% of your back garden?

It’s that term again – curtilage. To comply with permitted development rules, a building can’t take up more than 50% of your total curtilage. This 50% also includes any other buildings you may have in your garden. So if you have a garden room already, but you want to add a garage, and the combined area of both buildings is more than 50% of your total space, you’ll need planning permission. 

But if the garage won’t take up more than 50% of your curtilage, you can check this off your list.

Do permitted development rules limit the size of garage I can build?

While some of these rules refer to the height of the building’s roof and walls, permitted development rules don’t have much to say about the size of your building beyond how much of your garden and grounds it takes up. 

If your home is in a ginormous plot of land, your garage plus any other ancillary buildings can’t be more than 50%, but this would still allow you to build a great whacking huge garage, surely?

Technically, this is correct, but once your garage is bigger than 30m2, you’ve got an extra layer of admin to deal with. Any building over 30m2 will be subject to Building Control.

What’s the difference between planning permission and Building Control?

Hold on now. Building Control? This article is about planning permission! But these two sets of legislation are often related, and in some cases, both will apply to a garage project.

What is planning permission for?

You’ll need planning permission if your building doesn’t meet all the conditions for permitted development. Planning permission applications look at how your new building will impact the environment and those around you. 

If your garage plans involve putting a 3m high wall three inches away from your neighbour’s windows, the local council will have something to say about that. 

In a conservation area, the aesthetic appearance of the new building should be sympathetic to the surroundings. If you live in a street of gorgeous Victorian mansions, a prefab concrete garage will stick out like a sore thumb, and your neighbours aren’t likely to be too chuffed.

Planning permission deals with the environmental and social impact of your proposed project.

What is Building Control for?

Building Standards legislation makes sure that buildings are safe for habitation. The rules set out within Building Control ensure that any structure intended for living in will be built with robust construction methods and materials that result in a solid, fireproof, waterproof, sustainable building. 

While you most likely won’t want to live in your garage, the 30m2 limit applies both for safety and because it’s entirely possible to build a home in a structure of this size!

Building Control standards come with a certification process. First, you have to apply for a Building Warrant to cover the construction of your building. 

This involves hiring an architect and in some cases a structural engineer to ensure that your planned project meets the standards for Building Control. 

What happens once I apply for a Building Warrant?

Your local authority issues a Building Warrant. This includes the warrant itself, a copy of your proposed plans, and a Construction Compliance and Notification Plan (CCNP). The CCNP tells you when you need to contact your local building standards department, and when you need inspections at different stages of your work. 

Once your garage project is complete, you must submit a certificate of completion to prove that the work carried out meets the conditions of the warrant. This is then checked by a verifier from your local council.

Building Control can be a long, protracted, expensive process. There’s an application fee that depends on the size and value of your building. The architects and structural engineers will charge for their expertise, and depending on the scope of your project, you may need additional certification from other experts. There’s a fee for any amendments to the original warrant and for any extensions past the initial three-year period that the warrant covers. If you’d like to avoid these added expenses, keep your garage under 30m2.

Another good compromise is to add a carport for additional parking space. This doesn’t impact Building Control regulations but adds outdoor storage space or a covered area for your car. 

What’s the biggest garage you can build without planning permission?

A large Gillies and Mackay apex timber double garage with natural coloured timber, a grey garage door and a timber carport.

Permitted development rules mean that the only limitation to the size of a building that won’t need planning permission is the size of the land behind your home.

However, if you’re planning a building larger than 30m2, you will need a building warrant and all the associated admin to satisfy Building Control regulations.

If you still have questions about your project, book a Consultation with one of our Team. There’s no obligation, and you’ll get a definitive answer about whether or not your planned garage needs planning permission.

Read more:

Log Cabin Garage vs Gillies & Mackay Garage

How much does a large timber garage cost?

Is a timber garage big enough for my car?

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