Rear Extension Planning Permission

When does a rear extension need planning permission in England, and when can it fall under permitted development? Understand the national rules, the constraints that remove them, and how to check your exact property before paying for drawings.

Permitted development rights for rear extensions come from the same national legislation (the GPDO) right across England, but whether your project qualifies depends on the exact depth, height and storeys, the type of house, and the local designations on your specific address. The headline rules are national; the answer for your property is not.

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When it may be permitted development

These are the common features that keep a project on the simpler route.

The extension stays within the national single-storey depth and height allowances for your house type and uses materials similar in appearance to the existing dwelling.

The property still holds its full permitted development rights — they have not been withdrawn by an Article 4 direction or stripped by an earlier planning condition.

It is a clean rear addition that does not wrap around the side or alter the roof, and does not sit forward of the principal elevation.

When planning permission is more likely

These are the usual triggers that push a scheme beyond straightforward PD rights.

The extension exceeds the standard depth or height envelope, or is two-storey, taking it outside the permitted development limits set nationally.

The home is listed, in a conservation area, or covered by an Article 4 direction — these are applied locally and differ from one authority to the next.

The scheme combines rear and side elements, sits close to a boundary, or raises overlooking and overshadowing questions that warrant a full design review.

What CanUBuild checks

Faster answers before you speak to an architect or builder

The tool is designed to answer the first question most homeowners have: is this worth pursuing, and what is most likely to block it?

CanUBuild reads the address-level constraints for any property in England — conservation areas, listed status, Article 4 directions, flood risk and tree preservation orders — from national datasets.

The rear extension workflow asks only for the measurements that change the planning outcome: depth, ridge and eaves height, storeys, materials, side elements and boundary distance.

You also see decided applications near you, drawn from national and local planning records, so you can gauge how similar extensions fared with your own local planning authority.

FAQ

Questions people ask before starting a project

Are rear extension permitted development rules the same across England?

The underlying permitted development rights are national and apply across England, but the limits depend on your house type, and local designations such as conservation areas and Article 4 directions — which vary by authority — can remove or restrict them for your specific property.

How deep can a rear extension be without planning permission?

National permitted development sets standard single-storey depth allowances that differ for attached and detached houses, with a larger allowance available through the prior approval process. Whether your project fits depends on those limits and on whether your home still has its full PD rights.

Does my local authority change the rules?

Councils do not change the national permitted development limits, but they decide local designations — conservation areas and Article 4 directions — and they determine full planning applications against their own local plan policies. That is why the same extension can be straightforward in one authority and not in another.

Should I check feasibility before paying for drawings?

Usually yes. An address-level feasibility check tells you whether the project is likely to be permitted development, what local constraints apply, and what is most likely to block it — before you commit money to design work.

Next step

Check your property before paying for drawings

Search for the address, choose your project type, and get a planning feasibility answer based on permitted development rules, constraints, and local precedent data.

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