Explanation of Permitted Development & Building Regulations for Outbuildings

At Kennedy Garden Retreats, we design and install bespoke luxury garden rooms, garden office pods, and garden studios that elevate your lifestyle and add long-term value to your property. Whether you’re dreaming of a tranquil retreat, a professional workspace, or a creative studio, understanding planning requirements and building regulations is essential.

This page provides a comprehensive overview of permitted development rights, outbuilding classifications, and building regulations in the UK, to help you move forward with clarity and confidence.

Permitted developments rights are essentially a national grant of planning permission that enable homeowners to make improvements to their properties without the need to apply for planning permission from their local authority.

There are costs and delays associated with gaining planning permission. Permitted development rights were established to ensure that such inconveniences could be avoided when they would be out of proportion with the impact of the project on neighbours, the community and the environment.

We linked have access to Scotland and Wales government legistlation towards the end of this article, see England’s below.

Permitted development rights in England are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015, known as the GDPO.

Please be aware that permitted development rights do not apply to flats, maisonettes or listed buildings. It is also worth noting that permitted development rights may have been removed from any area or property by the local authority courtesy of an article 4 direction. It is always a good idea to check that your home has not been the subject of an article 4 direction by searching on the Council’s website. When planning permission was originally granted for your property, the Council may have added a planning condition removing permitted development rights – you can use the Council’s planning applications database to check this.

Permitted development rights are set out in Schedule 2 of the GDPO.
As permitted development rights encompass a wide variety of buildings and structures, the associated rules are divided into sections known as parts. The rules regarding developments within the curtilage of a house feature in Part 1 of the rules.

Part 1 of the rules is sub-divided into classes covering extensions, windows, roofs, loft conversions, chimneys, driveways, antennae and porches etc. Garden rooms are outbuildings which are covered by Class E.

Class E permitted developments include buildings constructed for a purpose that is incidental to the enjoyment of the dwellinghouse. Buildings which are attached to the house such as extensions are not permitted under Class E rights. They are covered by Class A permitted development rights.

It is the word ‘incidental’ that is key here, it is crucial to understand what incidental means in this context. The dictionary definition of incidental is “happening as a minor accompaniment to something else”. When it comes to garden buildings, purposes incidental to the house dont include usual residential uses. For example living accommodation including bedrooms, bathrooms and kitchens – although a small W.C. or shower room is sometimes allowed. A home office could be considered incidental if you don’t regularly receive visitors to it but a yoga studio would probably not be a permitted development if you use it to host classes. The studio would then be treated as commercial premises.

Unfortunately, there are specific limitations to permitted development rights that you should be aware of. Development is not permitted under Class E if:

1) Permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class M, N, P, PA or Q of Part 3 of the Schedule (change its use).

In other words, if your dwellinghouse was previously a commercial building and its use was changed, you may not be able to build a garden room without planning permission. The legislation regarding change of use is complex but can be explored here.

2) The total area of ground covered by buildings, enclosures and containers within the curtilage of the property (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse).

To see whether you can proceed with your garden room under your permitted development rights, you need to make the following calculations:

A – Calculate the total area of your curtilage.
B – Calculate the area covered by the original dwelling house (bearing in mind the definition of original outlined above).
C – Calculate the area covered by any outbuildings, enclosures and containers including your proposed garden room.
D – Calculate the area occupied by any additions to the original house such as extensions.

Then, confirm that the area covered by C + D would be less than 50% of A – B.

3) Any part of the building would be situated on land forward of a wall forming the principal elevation of the original dwellinghouse.

For the meaning of principle elevation, please see above. To establish whether your building would be forward of the principal elevation, consider a hypothetical line drawn through that elevation to the side boundary of the land surrounding the house. You would need planning permission if any part of the garden room would be forward of that line.

For example:

Note that if the principal elevation comprises more than one wall facing in the same direction, all such walls will form part of the principal elevation.

For example:

4) The building would have more than one storey.

Buildings, including garden rooms, that are to have more than one storey will always require planning permission.

5) The height of the building would exceed:

A)  4 metres in the case of a building with a dual-pitched roof or hipped roof (a roof that slopes on four sides).

B)  2.5 metres in the case of a building within 2 metres of the boundary of the curtilage of the dwellinghouse.

C) 3 metres in the case of a building with a mono-pitched-roof.

D) 3 metres in any other case.

The height of the building must be measured from the highest ground level immediately adjacent to the building and to its highest point. If your building is to be located within 2 metres of a boundary, the height restriction of 2.5 metres will mean your garden room will need to be completed by a flat roof.

6) The height of the eaves of the building would exceed 2.5 metres.

The eaves of a building are considered to be the lowest point of a roof slope or where a flat roof meets the outside wall of the building.

7) The building would be situated within the curtilage of a listed building.

8) The building would include a veranda, balcony or raised platform.

Note that for the purpose of permitted development, the term raised refers to a feature that is more than 0.3 metres above the ground.

9) The building is a dwelling or residential annexe.

In other words, if the garden room is to self-contained accommodation. The includes residential annexes or “granny annexes”, holiday lets/AirBnB and accommodation let to a tenant.

10) Position of Outbuilding

11) If the garden room is to be situated more than 20 metres from any wall of the dwellinghouse and would exceed 10 square metres, it would not be a permitted development if it is within the curtilage of a dwellinghouse which is within a World Heritage Site, a national park, an area of outstanding natural beauty or the Broads.

You should also note that in the specified locations, the total area of ground which may be covered by outbuildings that are more than 20 metres from any wall of a house is 10 square metres. This means that any existing structures such as sheds and greenhouses must be factored into your calculations.

In addition, outbuildings sited between a side wall and the boundary of the land surrounding the house are not permitted developments in a World Heritage Site, a national park, an area of outstanding natural beauty or the Broads.

ome projects that can proceed under permitted development rights will need to comply with building regulations. However, most garden rooms are exempt. The government’s Planning Portal states:

“Building regulations will not normally apply if the floor area of the building is less than 15 square metres and contains NO sleeping accommodation. If the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval providing that the building contains NO sleeping accommodation and is either at least one meter from any boundary or it is constructed of substantially non-combustible material“

ou have probably heard many anecdotes about problems with planning departments and seemingly unreasonable planning decisions. However you may be able to get advice on your garden room by ringing your local “duty planning service”. Planning departments are under a lot of pressure and some no longer offer this service in which case you may need to pay a fee for advice – details of this will be on the Council’s website.

If you need to apply either for a Certificate of Lawfulness (to get certainty that your garden room will be allowed under permitted development rules) or planning permission, you will require scaled elevations and a floorplan of your proposed garden room (at a scale of 1:100 or 1:50). You will also need a block plan (at a scale of 1:500 or 1:200) and a location plan (at a scale of 1:1250). The latter can be obtained via the Planning Portal for a small fee. You will need to complete the application form and you will need to provide details of the materials that will be used to construct the building and you will have to explain how you intend to control rainwater runoff from the structure. Your garden room supplier should be able provide all relevant information concerning materials and the management of rainwater.

There is a charge to make a planning application which must be paid at the time of submitting the application. It would typically take around 8 weeks to gain a planning decision, but the length of the process varies according to which local authority you are dealing with and how busy they happen to be when you apply.

Your garden room can likely be built under your permitted development rights if:

• Your dwellinghouse was not created by a change of use.
• The garden room does not feature accommodation.
• The building will not be attached to the dwelling house.
• Your outbuildings and additions including the garden room do not cover more than 50% of the curtilage of your dwellinghouse excluding the area covered by the dwelling.
• The garden room is not to be positioned forward of the principal elevation of the dwelling.
• The proposed building is single storey.
• The height of the building does not exceed 4 metres if it has a dual-pitched roof or does not exceed 2.5 metres if located within 2m of a boundary, or 3 metres in all other cases.
• The height of the eaves does not exceed 2.5 metres.
• The dwelling house is not a listed building

If your house is in a national park, conservation area, area of outstanding natural beauty or the Broads, you may still be able to build your garden room under permitted development, but the rules are different.

Permitted development rights are somewhat complex. But don’t be put off! Most garden rooms will prove to be permitted developments and your local planning office will help you to decide whether you need to make a planning application. A garden room will always be a significant asset and one that is worth tackling a few rules and regulations to achieve.

Kennedy Garden Retreats provide a planning application service where we deal with all aspects of the application for you, so please ask if you would like us to handle this.

The rules governing permitted development in Wales are very similar to those in England. However, if you are planning to build a garden room in Wales, please note the following limitations also apply.

Development is not permitted by class E if:

1. Any part of the building would extend beyond a wall comprised in a side elevation of the existing dwellinghouse and would be nearer to the highway than either the wall comprised in that side elevation which is nearest to the highway or any point 5 metres from the highway, whichever is the nearer to the highway.
2. Any part of the building would be situated within 2 metres of the dwellinghouse and exceed 1.5 metres in height.

Guidance regarding permitted development rights for householders in Wales can be found here.

Most permitted development rules in Scotland regarding garden buildings are similar to those that apply in England. However, there is one notable exception:

In the case of dwellinghouses located in conservation areas, the floor area of an outbuilding cannot exceed 8 square metres (4 square metres if within the curtilage of a listed building).

Householder permitted development rights guidance for Scotland is available here.