Rear Extension Planning Permission in London

Find out when a rear extension in London may fall under permitted development, when planning permission is more likely, and what constraints CanUBuild checks before you spend money on drawings.

Rear extensions are one of the most common home improvement projects in London, but the answer is not the same for every house. Depth, height, storeys, materials, proximity to boundaries, and local constraints can all affect whether you can rely on permitted development or need a full planning application.

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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 is modest in depth and height for the property type, uses materials similar to the existing house, and avoids obvious design conflicts.

The house still benefits from normal permitted development rights and is not heavily constrained by local designations or past planning conditions.

The proposal is a straightforward rear addition rather than a more complex mix of rear, side, and roof changes.

When planning permission is more likely

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

The extension is especially deep, tall, or two-storey in a way that falls outside the usual PD envelope.

The property sits in a conservation area, is listed, is covered by Article 4, or has other planning controls that limit automatic rights.

The proposal includes side extension elements, problematic boundary relationships, or details that may affect neighbours and trigger a fuller 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 checks address-level planning constraints such as conservation areas, listed building status, Article 4 directions, flood risk, and tree preservation orders before you commit to the project.

The rear extension workflow asks for the details that actually matter to the planning outcome, including depth, height, eaves height, storeys, materials, side elements, and boundary distance.

You also see nearby planning approvals and refusals so you can judge whether similar rear extensions have succeeded in your local planning authority.

FAQ

Questions people ask before starting a project

Do all rear extensions in London need planning permission?

No. Some rear extensions can be carried out under permitted development, but the answer depends on the size of the extension, the type of property, the surrounding constraints, and whether your property still has its normal PD rights.

Does being in a conservation area affect a rear extension?

Yes, it can. Conservation area controls can restrict permitted development rights and make a rear extension more likely to need planning permission or a more careful design response.

Why does boundary distance matter for a rear extension?

Boundary relationships can affect whether a scheme stays within common permitted development expectations and can also influence neighbour impact, overshadowing, and design acceptability in a planning application.

Should I check planning feasibility before paying for drawings?

Usually yes. A quick feasibility check helps you decide whether the project is likely to be straightforward, whether planning permission is likely, and which risks you should resolve before spending on 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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