Most single storey rear extensions do not need planning permission, because they fall under permitted development rights. But those rights come with strict size limits, and in Brighton and Hove there are extra catches, from conservation areas in the city centre to flats above shops along the Lewes Road. Here is how to work out where your project stands before you spend money on drawings.
Permitted development is a national set of rules that lets homeowners extend without a full planning application, provided the extension stays within set limits. For a single storey rear extension on a house, the key figures are how far it projects from the original rear wall: up to 3 metres for a terraced or semi detached house, and up to 4 metres for a detached one.
There are height limits too. The extension can be no taller than 4 metres overall, and if any part sits within 2 metres of a boundary, the eaves must stay at or below 3 metres. It also cannot cover more than half the land around the original house. Note the word original: if a previous owner already extended, that earlier work eats into your allowance, which catches out a lot of buyers of Victorian terraces in areas like Hanover and Preston Park.
If you want to go beyond 3 or 4 metres, there is a middle option called the larger home extension scheme. This allows a single storey rear extension of up to 6 metres on a terraced or semi detached house, or 8 metres on a detached one, without full planning permission. Instead, you notify Brighton and Hove City Council through a prior approval application, and they consult your neighbours.
If a neighbour objects, the council assesses the impact on their light and outlook before deciding. On the tight terraced streets common across Brighton, a 6 metre extension will often draw an objection, so it is worth talking to your neighbours before you apply rather than after. Prior approval is quicker and cheaper than a full application, but it only covers single storey extensions on houses, not flats.
Brighton and Hove has 34 conservation areas, covering much of the city centre, Kemptown, Clifton Hill, the Round Hill area and beyond. Inside a conservation area the larger home extension scheme does not apply, and some areas carry Article 4 directions that remove permitted development rights altogether, meaning even a modest extension needs a full application. Listed buildings, of which the city has plenty, need listed building consent for almost any alteration.
Flats and maisonettes have no permitted development rights at all, so any rear extension to a flat needs planning permission regardless of size. Given how much of Brighton's housing stock is converted flats, this is the single most common surprise we come across. If you are unsure of your property's status, the council's online planning map shows conservation area boundaries, or you can check with the planning department directly.
The safest route is a lawful development certificate. This is a formal confirmation from the council that your proposed extension is permitted development, and it costs roughly half the fee of a full planning application, which at the time of writing is several hundred pounds for householder schemes. It is not compulsory, but solicitors increasingly ask for one when you sell, so it is cheap insurance.
Whatever route you take, remember that planning permission and building regulations are separate. Every rear extension needs building regulations approval covering structure, insulation, drainage and electrics, even if no planning application is required. A decent builder or architect will factor both into the timeline: allow around 8 weeks for a planning or prior approval decision, plus design time before that.
Usually not, if it is on a house rather than a flat and stays within the height and boundary limits. Check first whether your home is in a conservation area or has already been extended, as either can change the answer.
Yes. Flats and maisonettes have no permitted development rights, so any extension needs a full planning application to Brighton and Hove City Council whatever its size.
If it needed permission, the council can serve an enforcement notice requiring alteration or removal, and it will cause problems when you sell. You can apply for retrospective permission, but there is no guarantee it will be granted, so it is far cheaper to check first.
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