For most homes in Aylesbury and the surrounding villages, a single storey rear extension can be built without a full planning application. That is thanks to permitted development rights, which set out what you can build as of right. The catch is that the limits are precise, and getting them wrong can mean an enforcement notice or an awkward conversation when you come to sell.
Permitted development lets you extend a house without applying for planning permission, provided the extension stays within fixed limits. For a single storey rear extension on a detached house, that means no more than 4 metres beyond the original rear wall. For a semi-detached or terraced house, the limit is 3 metres. The extension must be no higher than 4 metres overall, and if it comes within 2 metres of a boundary, the eaves cannot exceed 3 metres.
The word original matters. It means the house as it stood on 1 July 1948, or as first built if later. If a previous owner already added a conservatory or a small extension to the rear, that has used up some of your allowance. Side extensions have their own rules: single storey only, no wider than half the width of the original house, and no higher than 4 metres.
If you want to go further than 3 or 4 metres, there is a middle route between permitted development and a full application. The larger home extension scheme allows single storey rear extensions of up to 6 metres on semi-detached and terraced houses, and up to 8 metres on detached houses. You still have to notify Buckinghamshire Council through a prior approval process before you start.
The council writes to your adjoining neighbours and gives them 21 days to object. If nobody objects, you get confirmation and can go ahead. If a neighbour does object, the council looks at the effect on their amenity, mainly loss of light and outlook, and decides. There is no fee for this notification at present, but the extension still has to meet all the other permitted development conditions on height and materials.
Some situations take permitted development off the table altogether. Flats and maisonettes have no permitted development rights, so any extension needs an application. Listed buildings need listed building consent as well as planning permission. Many newer estates around Aylesbury, including parts of Berryfields, Kingsbrook and Buckingham Park, had permitted development rights removed as a condition of the original planning approval. Check your property's planning history on the Buckinghamshire Council website or ask us to check for you.
Conservation areas in the district, such as those in Wendover, Haddenham and parts of the old town, restrict side extensions and cladding. The Chilterns National Landscape covers villages to the south and restricts anything extending more than half the width of the house. A front extension almost always needs permission, as does anything that faces a road on a corner plot.
A householder application to Buckinghamshire Council currently costs 528 pounds and takes about 8 weeks once validated. Add architect's drawings and you are typically looking at 1,500 to 3,000 pounds before any building work begins. That is worth knowing early, because on a tight budget it can change whether you go for 3 metres or 5.
Planning permission and building regulations are two different things, and homeowners regularly confuse them. Even if your extension is permitted development, it still needs building regulations approval. This covers the structural design, foundations, insulation, drainage, fire safety and any new glazing. Buckinghamshire Council's building control team or an approved private inspector will visit at set stages, usually at foundations, damp proof course, drainage, and completion.
Foundation depth is a common issue locally. Much of Aylesbury sits on clay, and if there are trees nearby, building control will often ask for foundations of 1.5 metres or deeper. On a 3 by 5 metre extension, that can add several hundred pounds to the groundwork. The completion certificate at the end is what your solicitor will ask for when you sell, so keep it safe.
Start with a Lawful Development Certificate if you are relying on permitted development. It costs 264 pounds, half the fee of a full application, and gives you formal confirmation from the council that your extension does not need planning permission. It is optional, but buyers and mortgage lenders increasingly ask for it, and it removes any doubt if a neighbour later complains.
Check the Party Wall Act too. If your extension foundations are within 3 metres of a neighbour's building, or you are building on the boundary, you need to serve notice on them at least one month before starting. It is a separate process from planning and it catches people out when the digger is already booked.
Usually yes, as long as it is at the rear, no higher than 4 metres, uses similar materials, and your permitted development rights have not been removed. Check for restrictive conditions if the house was built after 2000 or is in a conservation area.
A householder application normally takes 8 weeks from validation, though it can be longer if the council asks for amendments. Prior approval for a larger extension takes 42 days, and a Lawful Development Certificate also takes up to 8 weeks.
Yes, a conservatory is treated exactly the same as any other single storey extension for planning purposes. It counts against your permitted development allowance and must meet the same size and height limits.
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