Can I build a 6-metre extension on my Wembley semi?

Possibly. Through the prior approval process, permitted development allows up to 6 metres on a semi if the council is satisfied about the impact on neighbours, and Brent's 2025 SPD supports up to 6 metres with planning permission, as long as it uses no more than half the garden. Neither route works the same way in a conservation area.

Do I need Thames Water's permission for an extension?

If the extension will be built over or close to a public sewer, you normally need a build-over agreement from Thames Water. Many Wembley semis have shared drains at the back, so we check before finalising the design.

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Extensions · Wembley

House extensions in Wembley

We build single-storey rear, side and wraparound extensions for houses in Wembley, most often turning the small kitchen of a 1930s semi into a kitchen-diner that opens onto the garden.

Area: Wembley
Planning authority: London Borough of Brent

Single-storey brick rear extension with a glazed hipped roof and dark grey sliding doors on a semi-detached house, opening onto a grey patio and lawn — AI-generated illustration; not a completed Mirion project.

What to know in Wembley

Extending a Wembley semi

A 1930s Wembley semi usually has a narrow kitchen at the back and a separate dining room, with a side passage or garage to one side and a long garden. The popular options are a full-width single-storey rear extension, a side extension replacing the garage or passage, or both combined in an L-shape. On older houses near Wembley Central that have a back outrigger, a side-return infill does the same job.

Brent's limits

With planning permission, Brent's 2025 SPD says single-storey rear extensions to semi-detached and terraced homes could be up to 6 metres deep, as long as they take up no more than half the garden, and side extensions should be no wider than two-thirds of the original house. Without an application, permitted development allows 3 metres, or up to 6 metres through the prior approval process. In the Barn Hill, Wembley High Street, Northwick Circle and Sudbury Court conservation areas, the SPD does not apply, side extensions always need permission and Article 4 directions apply.

Practical points in Wembley

Drains often run under the back of these houses, so we check sewer records early in case a build-over agreement with Thames Water is needed. Event-day parking restrictions around the stadium affect skips, deliveries and contractor parking, and we schedule around them.

How we approach extensions

Our process, from survey and design to building and handover, is explained on the main service page.

Go to our main extensions page

Wembley extensions: common questions

: Possibly. Through the prior approval process, permitted development allows up to 6 metres on a semi if the council is satisfied about the impact on neighbours, and Brent's 2025 SPD supports up to 6 metres with planning permission, as long as it uses no more than half the garden. Neither route works the same way in a conservation area.
: If the extension will be built over or close to a public sewer, you normally need a build-over agreement from Thames Water. Many Wembley semis have shared drains at the back, so we check before finalising the design.