Navigating Permitted Development for Home Improvements

Within UK planning law, Permitted Development Rights (PDR) grant the ability to undertake specific types of development without the need to obtain planning permission, which can save you time and money by avoiding the planning process entirely. The rights are useful for a wide range of home improvement projects and they’re currently expanding (DLUHC consultation 2024).

In this blog we provide a brief introduction to the Permitted Development Rights Classes that are most useful for homeowners looking to extend and improve their property.

Under Class A, homeowners may build rear and side extensions within the following limits:

Single storey rear extension

•  Max height of 4m
•  Max length (beyond the rear wall) of 4m* for a detached house, or 3m* for a terraced or semi-detached house
•  *The maximum length can be doubled subject to prior approval and neighbour consultation
•  Note that the rear wall is any wall directly opposite the front of the house, and the limit applies to each rear wall independently

Two-storey rear extension

• Height of roof and eaves must not exceed the original house
• Max length (beyond the rear wall) of 3m
• Must be at least 7m from the nearest boundary

Single storey side extension

• Max height of 4m
• Max width (beyond the side wall) of half the width of the original house
• Note that the extension must also comply with the limits for the maximum length beyond a rear wall where applicable

If your house is within a designated protection area i.e. conservation areas, national parks or areas of outstanding natural beauty, the permitted size of the rear extension is reduced, and the rights to build two storey rear extensions or side extensions are removed.

Single storey rear extension in a conservation area, national park or AONB

• Max height of 4m
• Max length (beyond the rear wall) of 4m for a detached house, or 3m for a terraced or semi-detached house
• Note that the rear wall is any wall directly opposite the front of the house, and the limit applies to each rear wall independently

In addition to the above and in all cases:

• Extensions are measured relative to the original house (as built, or as it was in 1948)
• The buildings (new and existing) must cover no more than 50% of the curtilage
• The extension must not extend beyond the front elevation or any roadside elevation
• Extensions within 2m of the boundary may not exceed 3m at the eaves
• Materials must be similar to the original house
• Upper floor windows on the side elevation must be obscured

Under Class B, homeowners may make additions or alterations to the roof, including dormer extensions, within the following limits:

Dormer Extensions

• Not permitted within a designated protection area i.e. conservation areas, national parks or areas of outstanding natural beauty
• Not permitted on the front elevation or any roadside elevation
• Must not increase the height of the roof
• Max roof space increase of 50 cubic metres, or 40 cubic metres for a terraced house
• Set back 20cm from the eaves of the original house (and original eaves maintained)
• Must not create a balcony, or other raised viewing platform
• Materials must be similar to the original house
• Windows on the side elevation must be obscured

Class E permits the development of outbuildings which are detached from the original house and ancillary to its primary function i.e. gyms, home offices, garages, stables, sheds and swimming pools. The outbuildings must be single storey and located behind the front elevation (or behind the rear elevation in conservation areas, national parks and areas of outstanding natural beauty). Class E can be very useful for establishing a legitimate ‘fall back’ position to support a potentially contentious application for properties in national parks or AONBs, but that is a subject for another blog.

As you will have guessed, there are other Permitted Development classes and lots of small print that can be used to your advantage if applied properly.

For further information, refer to the Town and Country Planning (General Permitted Development) (England) Order 2015 , and speak to an Architect or Planning Consultant if you need further advice.

About OB Architecture:

OB Architecture is an award-winning architectural firm delivering aspirational homes on coastlines and mountains, in cities and in the countryside. Established by Founder Olly Bray in 2010, OB Architecture is a friendly and open practice of experienced architects, designers and technicians. The team works between three architectural studios in London, Winchester and Chamonix delivering projects locally and internationally.

‘Our buildings deliver value. We design for people, and we’re passionate about delivering tangible value through considered and innovative design.’