Permitted development rights for extensions: build an extension without planning permission in 2020

Permitted development rights for extensions can allow you to transform your home by extending under permitted development – or, without planning permission. Why not find out how in this guide then spend the summer planning?

Permitted development rights for extensions: contemporary extension on house by variant office
(Image credit: Variant Office)

Gaining permitted development rights for extensions means that you can avoid having to apply for planning permission, so will need (slightly) less paperwork and will make a (slight) cost saving. It should also speed up the whole process a little. Extending under permitted development rights is entirely possible to do under the current rules.

Whether you’re considering building a single storey extension or double storey extension at the back of your house, you live in England, and you plan your extension carefully, you may well be able to avoid having to make planning application, building under permitted development rights instead. 

Follow our expert guide to find out how to achieve your extension project under permitted development rights – and find out all you need to know about extending a house in our ultimate guide. Do the legwork now over the summer, and get plans in place for autumn.

rear extension to victorian terraced house photographed by polly eltes: from our guide, Permitted development rights for extensions

(Image credit: Polly Eltes)

What are permitted development extensions?

Permitted development rights for extensions in the UK

Permitted development rights for extensions are granted in the form of General Development Planning Orders (GDPOs). These apply separately to England, Wales (opens in new tab), Scotland (opens in new tab) and Northern Ireland (opens in new tab), giving implied planning consent to carry out certain classes of development.

Under current permitted development rights for extensions (PD), you can plan and build a structure in the following ways without planning permission, as long as you adhere to certain guidelines.

If you are planning and designing a single storey extension, this means it can be up to 6m from the original rear wall of an attached house (or 8m on a detached property) and up to 4m in height. If your extension is to be within 2m of your property's boundary, the eaves height is limited to 3m.

If you are adding a double storey extension, it can’t be taller than the highest part of your existing roof; mustn't extend beyond the rear wall by more than 3m; must be at least 7m from the boundary; be built in materials to match the original structure; no two storey extensions can be made to the front of the house, or to any wall parallel to the highway. 

Consider, too, that if the roof of a double storey extension connects to your existing roof you will need to deduct the volume of the extension roof from any volume allowance you have in place for a loft conversion (for attached houses there is a loft dormer allowance of 40 cubic metres, and 50 cubic metres for detached properties; under PD, a two storey extension could have a roof element of 10 to 35 cubic metres). Any upper floor window in a wall or roof slope of a side elevation of a double storey extension must be non-opening and obscure-glazed, unless the opening parts are more than 1.7 metres above the floor of the room in which it is installed.

If you are adding a loft conversion, you can do so by up to 50m³ in a detached house, or by 40m³ in an attached home. Rooflights (use our guide to choose yours) that are flush or do not project further than 150mm are allowed, but you will need permission to add a dormer window on a roof elevation that faces the road.

Adding a porch can come under permitted development, too. Use our guide to find out more.

Bear in mind too that:

  • The extension must be built in accordance with the approved details, and use materials of a similar appearance to the rest of the house (confirm this with your local authority). This does not apply to conservatories;
  • The roof pitch of the extension must mimic that of the original house;
  • All extensions and outbuildings must not cover more than 50 per cent of the original garden area;
  • Any additions to your property since 1948 count towards your permitted development allocation, so it's important to do your research first. 

See for full conditions, and always double-check with your local council as each one can differ slightly in its approach.

To take advantage of relaxed permitted development rules relating to single storey extensions, you must also:

  • Live in England;
  • Not live within a conservation area, Area of Outstanding Natural Beauty, World Heritage Site or SSSI;
  • Live in a dwelling house, not a flat;
  • Seek prior approval.

In all cases, whatever your extension type and even if you fall within all these guidelines, it's vital that you check with your local authority that the specific project you are planning falls within permitted development rights before work begins.

The process of extending under permitted development

Before proceeding with your project under permitted development rights for extensions, ‘prior approval’ must be sought from the local planning authority, and a neighbour consultation scheme implemented. This process, done through your local authority, is to allow neighbours to be consulted, requiring a written description, with key dimensions and a to-scale site plan, to be submitted.

Prior approval does not automatically mean the development can proceed, as it does not negate any overriding interests such as restrictive covenants and easements, including rights of way and right to light, so always check title deeds. Listed buildings will also require listed building consent.

What to do if your neighbours object to your extension

If your adjoining neighbours do not object to your extension within the 21 day consultation period, the council will issue an permitted development rights approval notice. There is no application fee and the local authority has 42 days to respond from the date received. 

If neighbours do object, the council will consider the impact on the amenity of their property and decide whether it is reasonable to build an extension without planning permission. If the application is refused, there is an appeals process.

Can you add an extension under permitted development to all property types?

Permitted development rights for extensions apply to dwelling houses, not flats, so if you live in a ground floor apartment, for example, and want to extend the room at the back of the property, you will need to apply for planning permission.

Permitted development rights may also be restricted or removed by the local authority by planning conditions that were applied by a previous approval.

Bear in mind that the back of a property is taken as the original rear wall, or as the building stood on 1 July 1948, so this could affect the size of extension allowed, or if permitted development is applicable. If the original wall has changed, check what’s allowed with your local authority.

Permitted development and outbuildings

Not strictly an adjoining extension, outbuildings, whether a summerhouse for garden lounging or a home office at the end of the garden, nevertheless add extra living space that counts towards your home's overall square footage.

Permitted development rules for these type of extensions don't just cover sheds and summerhouses, but also playhouses, greenhouses and garages and sauna cabins. Plus, and this may surprise you, they also include kennels, enclosures, such as tennis courts, swimming pools and even ponds.

These structures are generally covered by permitted development, dependent on a few conditions, such as eaves height being limited to 2.5m, and overall roof height to 4m with a dual pitched roof or 3m for any other roof. You can find all the exceptions and rules on the government's dedicated page (opens in new tab). And, of course, it's always worth speaking directly to your local planning department before you consider extending without planning permission.

Applying for a Lawful Development Certificate for your extension

If you are adding more space under permitted development rights for extensions, it's a good idea to apply for a Lawful Development Certificate (LDC). 

This proves that your extension is lawful and does not require planning permission. It is not compulsory to have an LDC, but there may be times – such as when you are moving house – when you might need one.

Find out more on the government's LDC page (opens in new tab).

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Lucy is Global Editor-in-Chief of Homes & Gardens having worked on numerous interiors and property titles. She was founding Editor of Channel 4’s 4Homes magazine, was Associate Editor at Ideal Home, before becoming Editor-in-Chief of in 2018 then moving to Homes & Gardens in 2021. She has also written for Huffington Post, AOL, UKTV, MSN, House Beautiful, Good Homes, and many women’s titles. Find her writing about everything from buying and selling property, self build, DIY, design and consumer issues to gardening.