What this checker is for

Planning rules for home extensions in England can be hard to pin down from a quick internet search. This tool helps you work out whether your proposed extension is likely to fall under permitted development, or whether you will need to apply to your local council for planning permission before work starts.

It gives you a plain English steer based on the details you enter, so you know which route to take and what to look into next.

Who should use it

It is aimed at homeowners thinking about a rear or side extension, a two storey addition, a wrap around, or a loft conversion that extends the footprint of the house. It is also useful if you are buying a property and want to sense check what might or might not be allowed later.

It is less suitable for flats, maisonettes, and commercial buildings, where different rules apply. If your home is listed, in a conservation area, a national park, or an Area of Outstanding Natural Beauty, the tool will flag the extra restrictions that usually apply, but you should still speak to your council or a planning consultant before committing to plans.

How it works

You answer a short set of questions about the property and the extension you have in mind, things like the type of house, how much has already been built on, the size and height of what you are planning, and whether the site has any special designations. You then get a summary telling you whether it looks like permitted development, whether a lawful development certificate would be sensible to confirm that, or whether a full planning application is the likely route. Your answers are not stored and nothing is shared with your council, it is purely for your own use to help you decide what to do next.