{"id":7510,"date":"2026-08-10T08:49:01","date_gmt":"2026-08-10T08:49:01","guid":{"rendered":"https:\/\/www.buildteam.com\/blog\/?p=7510"},"modified":"2026-08-14T15:16:27","modified_gmt":"2026-08-14T15:16:27","slug":"permitted-development-for-extensions-and-loft-conversions","status":"publish","type":"post","link":"https:\/\/www.buildteam.com\/blog\/permitted-development-for-extensions-and-loft-conversions\/","title":{"rendered":"Permitted Development: A London Homeowner’s Guide to Extensions and Loft Conversions"},"content":{"rendered":"

One of the first questions people ask when planning an extension or loft conversion is “do I need planning permission?” The answer is not always straightforward. Many home improvements can be built under permitted development, a national right granted by government rules, but plenty still need a full application, and in much of London those rights have been removed street by street. This guide explains what you can build without planning permission, where the limits are, and why you should always check your own address before you start.<\/p>\r\n

Do I need planning permission?<\/h2>\r\n

There are really four possible answers to this question, and the biggest misconception is that permitted development means no process at all. The four answers are:<\/p>\r\n

    \r\n
  1. No, it is permitted development, and you can build as of right.<\/li>\r\n
  2. No, but you need prior approval first, for example a larger rear extension or adding storeys.<\/li>\r\n
  3. Yes, you need full planning permission.<\/li>\r\n
  4. It depends on your street, because an Article 4 direction or a conservation area has removed your rights.<\/li>\r\n<\/ol>\r\n

    Understanding which of these applies to you is the whole game. Getting it wrong leads to costly delays and changes, so it is worth taking the time to establish it early.<\/p>\r\n

    What is permitted development?<\/h2>\r\n

    Permitted development rights were designed by government to simplify the planning process for homeowners, by allowing certain improvements, including some extensions, without a full planning application. The rules come with their own restrictions on design, height and cubic size, and on how close the work sits to a neighbour. They vary with the type of property and its location, and they do not apply, or apply with extra restrictions, to flats, maisonettes, listed buildings, homes in conservation areas, and properties covered by an Article 4 direction.<\/p>\r\n

    Even where work qualifies, it still has to meet Building Regulations, and many homeowners apply for a Lawful Development Certificate from their council. That certificate confirms the work was legal, and it is a valuable document to show a buyer when you sell.<\/p>\r\n

    One point that catches people out: “original house” means the property as it was built, or as it stood in 1948. A previous owner’s extension uses up part of your allowance.<\/p>\r\n

    How big a rear extension can I build without planning permission?<\/h2>\r\n

    It is always best to confirm the full criteria with your local planning department, but here is where the limits sit as things stand.<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Project type<\/th>\r\nPD limit<\/th>\r\nKey conditions<\/th>\r\n<\/tr>\r\n
    Single-storey rear (as of right)<\/td>\r\n3m deep (terrace\/semi), 4m (detached), from the original rear wall<\/td>\r\nMax 4m high; 3m eaves within 2m of a boundary; materials to match; not on designated land<\/td>\r\n<\/tr>\r\n
    Single-storey rear (larger home extension)<\/td>\r\n6m (terrace\/semi), 8m (detached)<\/td>\r\nNeeds prior approval and neighbour consultation; not on designated land<\/td>\r\n<\/tr>\r\n
    Side extension<\/td>\r\nSingle storey, max 4m high, width up to half the original house<\/td>\r\nNot on designated land; not forward of the front wall<\/td>\r\n<\/tr>\r\n
    Two-storey rear<\/td>\r\nMax 3m beyond the original rear wall<\/td>\r\nAt least 7m from the rear boundary; not on designated land; no 6m\/8m route<\/td>\r\n<\/tr>\r\n
    Two-storey side<\/td>\r\nNot permitted development<\/td>\r\nAlways needs planning permission<\/td>\r\n<\/tr>\r\n
    Loft conversion<\/td>\r\n40 cubic metres (terrace), 50 (semi\/detached), by volume<\/td>\r\nNo dormer beyond the roof slope facing a road; not above the ridge; 20cm eaves set-back (except hip-to-gable); previous roof work counts<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n

    Ground floor extensions<\/h3>\r\n
    \"Diagram\r\n
    What is allowed (orange) and not allowed (blue) for a ground floor extension under permitted development.<\/figcaption>\r\n<\/figure>\r\n

    These can be built under permitted development, within limits. The total area of buildings other than the original house cannot cover more than half the land around it. A single-storey rear extension can go 3 metres deep on a terrace or semi, or 4 metres on a detached house, as of right from the original rear wall, and up to 6 or 8 metres via the larger home extension route where the council consults the neighbours. The extension cannot be higher than the original house, the eaves cannot exceed the original eaves, balconies and raised platforms are not allowed, and the materials must match the original house.<\/p>\r\n

    Side, wraparound and two-storey extensions<\/h2>\r\n

    Side extensions<\/strong> can be permitted development but must be single storey, no wider than half the original house, no more than 4 metres high, with eaves no higher than 3 metres if within 2 metres of a boundary, and in matching materials.<\/p>\r\n

    Wraparound extensions<\/strong> usually are not permitted development, because they combine a rear and a side extension and are often larger than the limits allow. They can occasionally qualify if the side and rear parts each qualify on their own and the combined design stays within all the limits, but larger wraparounds generally need planning permission.<\/p>\r\n

    Two-storey side extensions<\/strong> always need planning permission. Some two-storey rear extensions can be permitted development if they sit at the rear, extend no more than 3 metres beyond the original rear wall, keep at least 7 metres from the rear boundary, match the roof pitch where possible, and use obscure glazing on upper side windows.<\/p>\r\n

    Is my loft conversion permitted development?<\/h2>\r\n
    \"Diagram\r\n
    What is allowed (orange) and not allowed (blue) for a loft conversion under permitted development.<\/figcaption>\r\n<\/figure>\r\n

    Many loft conversions are, and the rules are based on the cubic size of the conversion. The volume of the new roof space must not exceed 40 cubic metres on a terraced house, or 50 cubic metres on a semi-detached or detached house. The new roof cannot be higher than the existing one, materials must match, and any side windows must be obscure-glazed and 1.7 metres above the floor.<\/p>\r\n

    One thing worth stating plainly: this allowance is measured in cubic metres of volume, not square metres of floor area<\/strong>. A lot of people get that wrong. A hip-to-gable conversion<\/a> can usually be done under permitted development, while a mansard<\/a> almost always needs full planning permission.<\/p>\r\n

    Where permitted development does not apply<\/h2>\r\n

    Some properties are subject to stricter rules, which means an application may be needed even for work below the size limits:<\/p>\r\n