Do I Need Planning Permission for an Extension?

Two different questions

Planning permission asks whether you may build the thing at all, judged on its effect on the area, the street scene and your neighbours. Building regulations approval asks whether what you build is structurally sound, safe and adequately insulated.

You may well not need the first. You will always need the second. Conflating them is the most common misunderstanding in the whole process.

What permitted development covers

Permitted development is a national grant of planning permission for specified householder works, subject to conditions. Extensions are included within limits that vary by extension type and by whether the house is detached, semi detached or terraced.

The conditions cover how far you may project, how tall the extension may be, how close it may come to a boundary, how much of the garden may be built on, and what it may be made of. Exceeding any single limit takes the whole scheme out of permitted development.

Projection limits are larger for detached houses than for others · Extensions must not exceed set heights, with tighter limits near a boundary · There is a cap on how much of the original garden may be covered · Side extensions are limited to single storey and to half the width of the house · Materials must be similar in appearance to the existing house · Verandas, balconies and raised platforms are excluded

Properties that do not have these rights

Some homes have restricted or no permitted development rights, and this is checked at the beginning rather than discovered later.

Flats and maisonettes have no householder permitted development rights · Listed buildings require listed building consent for most alterations · Conservation areas carry tighter limits, particularly on side extensions and cladding · Article 4 directions can remove rights across a defined area · Planning conditions on newer estates frequently remove them for individual houses

The larger home extension procedure

There is a route allowing larger single storey rear extensions than the standard limits, through a prior approval process rather than a full application. The council notifies the adjoining neighbours, and if any of them objects the council decides whether the impact is acceptable.

It is quicker and cheaper than a full application but it is not automatic, and it must be applied for before work begins. Building first and applying afterwards is not an option under this route.

How to check your own address

Search the council's planning portal for your address to see previous applications and the conditions attached to them. Check the council's mapping for conservation area boundaries and Article 4 directions. Check your title deeds for restrictive covenants, which are a private matter separate from planning but can still prevent building.

For a definitive answer, ask the local planning authority. Nothing here overrides what your council says about your property, and a short pre application enquiry is far cheaper than a refusal.

Getting it confirmed in writing

Where the work genuinely is permitted development, apply for a lawful development certificate. It is not required, but it is formal confirmation that permission was not needed, and it answers the question a buyer's solicitor will eventually ask.

Frequently asked questions

How long does a planning application take?

Householder applications carry a statutory determination period of eight weeks from validation, and validation itself can take a little time if anything is missing from the submission.

Can I start work while the application is being decided?

No. Building before a decision risks enforcement action and leaves you with no fallback if the application is refused.

Does a neighbour's objection mean refusal?

No. Objections are considered against planning policy, and matters such as loss of a view or disruption during construction are not grounds for refusal. Overlooking, loss of light and overbearing impact are.

What if I build without permission?

The council can require changes or removal. There are routes to apply retrospectively, but they carry real risk and are far more expensive than applying first.