Tools · Do I need planning permission?

Do you need planning permission for a side extension?

A single storey side extension can be permitted development, but the limits are tighter than for a rear extension and it is not permitted development at all on designated land.

Across the 283 councils we track, 84% of 59,811 decided side extension applications were approved, and typical council decision times run 8 to 10 weeks (public planning record to 10 Jul 2026).

First, about your home

What kind of home is it?

These permitted development rights apply to houses. Flats and maisonettes do not have them.

Is the building listed?

Work to a listed building usually needs listed building consent as well as planning permission. Outbuildings and boundary walls within the grounds of a listed building also need permission.

Is your home in a conservation area, National Park, the Broads, an area of outstanding natural beauty, or a World Heritage Site?

The rules call this designated land. Several permitted development rights are reduced or removed there. If you are not sure, your council's website says which areas are designated.

Now, about a side extension

Will it have more than one storey?
Will any part of it be taller than 4 metres?
Will it be wider than half the width of the original house?
Is any of it in front of the main front wall of the house?
Counting existing extensions and outbuildings, will more than half of the land around the original house end up built on?

0 of 8 questions answered. Answer them all to see where your project stands. Not sure is always an option.

What actually happens in your council

If you do end up applying, real decisions show what to expect. Pick your council for its approval rate and typical decision time for side extension applications, from the public planning record.

The rules this checker tests, cited

England’s permitted development limits for a side extension, checked against the official guidance on 2026-07-17. Every rule links to its source.

Building Regulations are separate from planning. A side extension needs Building Regulations approval regardless of planning: structure, insulation, drainage and electrics are all covered.

If permission is needed: usually a £548 application in England (fees from 1 April 2026, indexed each year, per the official fee guide (opens in new tab)). A Lawful Development Certificate for a proposed project is £274.

If you take it forward

Real planning history beats promises. See which architects and agents know your council, check approval odds by council and project, or browse traders with public evidence:

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Common questions

Do I need planning permission for a side extension in England?

Often not: A single storey side extension can be permitted development, but the limits are tighter than for a rear extension and it is not permitted development at all on designated land. Every limit has to be met, the rights apply to houses (not flats), and they can be removed locally by an Article 4 direction or a condition on an earlier permission. A Lawful Development Certificate from your council is the way to be certain.

Will it have more than one storey?

A side extension must be single storey to be permitted development. Source: GPDO Schedule 2, Part 1, Class A, paragraph A.1(j).

Will any part of it be taller than 4 metres?

A side extension must not be taller than 4 metres. Source: GPDO Schedule 2, Part 1, Class A, paragraph A.1(j).

Will it be wider than half the width of the original house?

A side extension must not be wider than half the width of the original house. Source: GPDO Schedule 2, Part 1, Class A, paragraph A.1(j).

Is any of it in front of the main front wall of the house?

Extensions are not permitted development in front of the principal elevation. Source: GPDO Schedule 2, Part 1, Class A, paragraph A.1(d).

How much does a planning application for a side extension cost?

If permission is needed, this kind of project is usually a £548 application in England (fees from 1 April 2026, indexed annually). A Lawful Development Certificate for a proposed project costs half the application fee.

Guidance from the public rules, not legal advice. Your council has the final say. The rules on this page are England law; Wales, Scotland and Northern Ireland have their own versions.

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