What are permitted development rights?
They are a national grant of planning permission set out in the Town and Country Planning (General Permitted Development) Order. They apply to houses, not flats or maisonettes, and only if the rights have not been removed.
Single storey extensions under permitted development
Single-storey rear extensions: 3m for attached properties and 4m for detached properties. Extensions cannot be attached to any existing extension or be a wrap-around extension. For all Permitted Development extensions, the materials and external finish should match the existing property.
Those limits are measured from the original rear wall of the house, and the extension must not exceed 4 metres in height, or 3 metres if it is within 2 metres of a boundary. It must not cover more than half the garden around the original house, counting earlier extensions and outbuildings.
What else can usually be done
- Single storey side extensions up to half the width of the original house, where they do not face a road
- Loft conversions with rear dormers within volume allowances, 40 cubic metres for terraced houses and 50 cubic metres for semi-detached and detached houses
- Outbuildings such as garden rooms, within height and coverage limits
- Small porches
- Rooflights that do not project more than 150mm
Planning applications
- Householder planning applications for extensions and alterations
- Lawful development certificates confirming permitted development
- Prior approval applications for larger single storey rear extensions
The original house
Many limits refer to the original house, meaning the house as it was first built or as it stood on 1 July 1948. Previous extensions, even by earlier owners, count towards the allowances. This is a common pitfall, so we check planning history carefully.
Materials and appearance
Permitted development is not a free hand on design. Materials used on the exterior should match the existing house, and side-facing upper windows have to be obscure glazed and fixed below a set height. A contemporary extension with very different materials will usually need a planning application, even if its size would otherwise be within the limits. That is often the right choice anyway, because a full application allows more design freedom.
Where rights are restricted
Permitted development rights are reduced or removed:
- On designated land, including conservation areas and National Parks such as the South Downs
- For listed buildings, where listed building consent is needed
- Where a planning condition has removed them, common on newer estates
- Where an Article 4 direction applies
Prior approval for larger rear extensions
The prior approval route allows larger single storey rear extensions, up to 6 metres for attached houses and 8 metres for detached houses, provided neighbours' objections are considered by the council. It is a quicker process than a full application but still needs drawings and a submission.
Common mistakes
The mistakes we see most often are counting from the wrong wall, forgetting an earlier extension built by a previous owner, assuming a new estate has full rights when a condition has removed them, and treating a wraparound as two separate permitted extensions. Each of these can turn a project that seemed straightforward into one that needs an application, so it pays to check before any drawings are finalised. Our guide on whether you need planning permission for an extension covers the alternatives.
Making it official
A lawful development certificate confirms your project meets the rules. It provides peace of mind for you and future buyers. We prepare the drawings and submit the certificate application as part of our planning applications service.
Outbuildings and garden rooms
Outbuildings such as garden offices, gyms and summerhouses can often be built under permitted development, provided they are single storey, are not forward of the principal elevation, stay within height limits that depend on how close they are to a boundary and do not cover more than half the garden. They must be used for purposes incidental to the house, so a garden room with a bedroom and bathroom for someone to live in is treated differently. Our page on annexe plans explains that distinction.
This guide is general information only and does not replace advice on your specific property. Rules can change, so always check the current position before starting work.
Want a professional to handle it?
Tell Signature Design and Architecture about your project.
Covering Hampshire.
Frequently asked questions
Does permitted development apply to flats?
No. Flats and maisonettes do not have householder permitted development rights, so extensions and loft conversions to them need planning permission.
How far can a single storey rear extension go under permitted development?
3m for attached properties and 4m for detached properties, measured from the original rear wall, with further conditions on height, materials and garden coverage.
Do earlier extensions count towards permitted development?
Yes. The limits relate to the original house, so extensions built by previous owners count towards the allowances.
Can I use a different material from my house?
Under permitted development, the materials and external finish should match the existing property. A contrasting design usually needs a planning application.
Is prior approval the same as permitted development?
Prior approval is a variation that allows larger rear extensions, but the council must be notified and neighbours can comment before you build.