For most homes in Croydon, the honest answer is: probably not. A large share of single storey extensions can be built under permitted development rights, which means no planning application at all. But the rules have hard limits on depth, height and boundaries, and getting them wrong is expensive to unpick.
Permitted development rights let you extend a house without a planning application, provided the extension stays within set limits. For a single storey rear extension on a semi-detached or terraced house, that means extending up to 3 metres beyond the original rear wall. On a detached house, you get 4 metres. The extension must 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.
One point that catches people out: the limits are measured from the original house as it stood in 1948, or as it was first built if newer. If a previous owner already extended, that counts against your allowance. We see this regularly in Croydon's Victorian terraces around Addiscombe and South Norwood, where old lean-to additions eat into what you can add now.
If 3 or 4 metres is not enough, there is a middle route. Under the larger home extensions scheme, you can build a single storey rear extension up to 6 metres deep on an attached house, or 8 metres on a detached one, without full planning permission. Instead, you submit a prior approval application to Croydon Council, and they notify your neighbours.
If the neighbours do not object within the consultation period, the council will usually issue approval within 42 days. If a neighbour objects, the council assesses the impact on their light and outlook and decides from there. It is quicker and cheaper than a full application, but it is not a formality, so it pays to talk to your neighbours before the letter from the council lands on their doormat.
Some situations take permitted development off the table entirely. Flats and maisonettes have no permitted development rights, so any extension needs a full application. The same applies to houses in conservation areas for certain works: Croydon has around 20 conservation areas, including the Webb Estate in Purley, Park Hill and parts of Norwood, and side extensions and cladding are restricted in them. Listed buildings need listed building consent on top of everything else.
Some properties also have an Article 4 direction or a planning condition from a previous approval that removes permitted development rights. This is common on newer developments. It is worth checking your title deeds and the council's planning register before assuming you are covered. Wraparound extensions, which combine a rear and side extension in one, usually need a full application too, because they fall outside the standard limits.
A householder planning application in England currently costs £528, and Croydon Council aims to decide within 8 weeks. Prior approval for a larger extension costs less and runs on the 42 day clock. Even when no permission is needed, we always recommend applying for a lawful development certificate, which costs half the planning fee and gives you formal proof the work was legal. Buyers' solicitors ask for it, and without one a future sale can stall.
Whatever route you take, building regulations approval is a separate requirement and always applies to an extension. It covers the structure, insulation, drainage and electrics rather than how the extension looks. A decent builder will handle building control inspections as part of the job, but do not let anyone tell you that avoiding planning also means avoiding building control. It does not.
A householder application should be decided within 8 weeks of validation, though complex cases can take longer. Prior approval for a larger single storey extension works to a 42 day deadline.
Often not, provided it is single storey, no wider than half the original house, and within the height limits. In a conservation area, though, side extensions need a full planning application.
The council can serve an enforcement notice requiring you to alter or demolish the work, and there is no fine that makes it go away. 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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