An outbuilding is a non-habitable building in the grounds of your home. What you choose to use it for is up to you, but popular uses include games rooms, offices, sauna cabins and extra storage. They usually fall under Permitted Development (PD) and should therefore not need planning permission, but read on to find out more.

Garden Room Uses

A room in your garden is a great way to create space for activities that you may not be able to accommodate in the home. Many people find that for practical (and monetary) reasons they cannot extend their home, but have plenty of room in the garden.

These are some of the most popular purposes for an outbuilding:

  • Office
  • Sauna cabin
  • Pool house
  • Storage
  • Plant room
  • Kennel
  • Games room
  • Studio

Most of these uses will mean having a connection to an electricity source is a must. And, if you plan to spend any length of time in the room then insulation will also be essential — especially if you plan to use the room in winter.


Where you choose to situate your outbuilding will partly be dictated by what space is available in your garden. If you need to link it to utilities then placing it fairly near the house is best, or it will cost more to connect it up (unless you can use off-grid sources of power, heat and water).

If you are using the outbuilding as a plant room, this will need to sit as close to the house as possible. If it is to also act as a garage, location will be dictated by where access to the site is.

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However, if you plan to use the room for relaxation – or as a den for the kids where you don’t have to worry about how much noise they make – then you may want it to be a bit further away from your home, and the neighbours’ homes too.

Planning Permission for Outbuildings

An outbuilding must serve the main house and not be independent from it, meaning you can’t use it as self-contained accommodation, or as a bedroom, bathroom or kitchen. Therefore, without planning permission an outbuilding could not be an annexe to house an elderly relative or teenager, and using it as a holiday let is certainly out of the question.

However, if the outbuilding is ancillary to the main dwelling and not used as a residence, if built within size limitations, it will be covered under your Permitted Development rights (alterations you can make without planning permission).

Outbuildings are not covered by Permitted Development in the grounds of a listed home, so you will have to apply for planning. If your home is in an Area of Outstanding Natural Beauty, National Park, Conservation Area or other type of specially designated land, then you will not be able to build an outbuilding to the side of the property. For it to be covered by PD it must also be at least 20m away from the property and be 10m2 or less.

On all other homes, outbuildings may not be built forward of the principal elevation without planning permission. Size restrictions for PD are explained below.


To be covered in your Permitted Development rights, outbuilding must be:

  • single storey;
  • have a maximum eaves height of 2.5m;
  • have a maximum overall height of 3m (or 4m on a dual pitched roof to the highest point).

If within 2m of a boundary then the height limit is 2.5m (meaning a flat roof may be best).

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You can also not cover more than 50% of your garden with buildings (you must include sheds and extensions in this calculation).

It is still a good idea to check with your local planning department before building, and apply for a Lawful Development Certificate, to prove the work was allowed.

Designing a Garden Room

If you are building near a boundary then your outbuilding can’t exceed 2.5m in height. Therefore, it may be best to opt for a flat roof and a contemporary design that complements this.

In cases where you are not restricted to 2.5m (or will be applying for planning permission so you can build exactly what you want), building in the same style as your home may make sense. However, be aware that unless you can get an exact material match, it may look better if you opt for a similar form, but different materials. Timber cladded barn styles work well with both contemporary and traditional homes.

Windows and Doors

Windows and doors also need to be considered carefully. Place the door so that it optimises the space inside, but is easily accessible from outside too. This will mean thinking about paths and potentially obtrusive plants in the surrounding area.

Studio rooms, pool houses and offices will benefit from large windows, allowing in plenty of light. However, you need to ensure that these will allow for glare-free spots if you are using a computer in there. Also consider security — don’t make it like a shop window, exhibiting all of your possessions inside to passing gazes.

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