Free tool · England

Do you need planning permission?

Answer a few questions about your house and project. The checker applies the national permitted development rules for houses in England and tells you which way it's likely to go, and why.

Your house

What kind of property is it?

Is it a listed building?

NoYesNot sure

Is it in a conservation area, National Park, National Landscape (AONB), the Broads or a World Heritage Site? Your council's website or planning map will say.

NoYesNot sure

Have permitted development rights been removed? This happens through an Article 4 direction or a condition on an earlier planning permission, often on newer estates.

NoYesNot sure

Would all extensions and outbuildings together cover more than half the garden? Measure the land around the house as it was originally built.

NoYesNot sure

Your project

What are you planning?

How far it sticks out from the back wall (m)

Highest point (m)

Width of the original house (m)

Does that side of the house face a road?

NoYes

Distance from the extension to the back boundary (m)

Will any part be within 2m of a boundary?

NoYes

Height of the eaves, where the roof meets the wall (m)

Extra roof space added (cubic metres) For a box dormer: width × depth × height ÷ 2 is a fair rough guide. Your designer can confirm.

Would it change the roof slope at the front of the house, facing the road?

NoYes

Would any part be higher than the existing ridge of the roof?

NoYes

Does it include a balcony, Juliet balcony platform or roof terrace?

NoYes

Any new side-facing windows that are clear glass or open below 1.7m?

NoYes

Highest point (m)

Eaves height (m)

Floor area (m²)

Roof shape

Would it sit in front of the house (the side facing the road)?

NoYes

Will any part be within 2m of a boundary?

NoYes

Will anyone sleep in it, or use it as a separate home or annexe?

NoYes

Is it to the side of the house, between the house and the side boundary?

NoYes

Is it more than 20m from the house?

NoYes

Most likely outcomeAnswer the questions

What to do next

For certainty, apply to your council for a Lawful Development Certificate before you build. It's the formal proof that no planning application is needed, and buyers' solicitors often ask for it.
Building regulations are separate and usually still apply.
Work on or near a shared wall may need a party wall agreement with your neighbours.

Price the project

A guide to the national rules for houses in England, not legal advice. Councils interpret some details differently. Based on the government's technical guidance on householder permitted development. Nothing you enter leaves your device.