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Advice · Port Talbot & Swansea

Do You Need Planning Permission for a Single Storey Extension?

Most single storey extensions in Swansea go ahead without a full planning application, but Wales has its own rules that catch a lot of people out. Here is how permitted development works locally, what the size limits actually are, and when you genuinely need to apply to the council.

Published 11 July 2026

Permitted development in Wales is stricter than England

A single storey extension often falls under permitted development, meaning you can build without a planning application. But Wales never adopted the larger allowances England brought in, so the numbers you read on many UK websites do not apply here in Langland or anywhere else in Swansea.

In Wales, a single storey rear extension can extend up to 3 metres from the original rear wall for an attached or terraced house, or 4 metres for a detached house. Maximum height is 4 metres overall, and where the extension sits within 2 metres of a boundary, the eaves must be no higher than 3 metres.

Where you live changes everything

Langland sits close to the Gower, which was the first designated Area of Outstanding Natural Beauty in the UK, and parts of the area fall within conservation areas. If your property is in a conservation area, an AONB, or is listed, your permitted development rights are reduced or removed entirely.

In these locations, cladding, side extensions and larger rear projects usually need consent even when the same work would be permitted a few streets away. It is always worth checking your specific address rather than assuming.

How to check before you spend anything

Swansea Council holds the planning history for your property, and you can search it online or ring the planning duty line. If your rights have been removed by a previous planning condition, an Article 4 direction, or the property type, you will need to apply regardless of size.

For peace of mind, many homeowners apply for a Lawful Development Certificate. It is not planning permission, but it is written confirmation from the council that your extension is lawful, which matters enormously when you come to sell.

Building Regulations still apply either way

This trips people up constantly: planning permission and Building Regulations are two separate things. Even if your extension is fully permitted development and needs no planning application, it still has to meet Building Regulations for foundations, structure, insulation, drainage and fire safety.

That means a Building Control inspection process whatever the size. Skipping it causes the same sale problems as skipping planning, so budget for both from the start.

Frequently asked

Common questions

Does a small rear extension always avoid planning permission?

Not always. A rear extension within the 3m or 4m Welsh limits is usually permitted development, but conservation area status, an Article 4 direction, or a previously removed right can mean you still need to apply.

How close to my neighbour's boundary can I build?

You can build up to the boundary under permitted development, but if the extension is within 2 metres of it the eaves height is capped at 3 metres. You may also need a Party Wall agreement, which is separate from planning.

Is a Lawful Development Certificate worth getting?

For most homeowners, yes. It costs less than a full application and gives you formal council confirmation that the work was lawful, which almost always gets asked for when you sell.

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