Extension Electrics in London: Planning Power for a Rear or Side Return Extension

Rear and side return extensions are one of the most common building projects in London, turning a narrow galley kitchen into a big open plan space. The new room usually brings new lighting, sockets, a kitchen, underfloor heating and sometimes a garden door with outdoor lights. Planning the electrics early saves money and avoids awkward changes later.

Check the existing supply and board first

An extension adds a lot of load, especially with a new kitchen, induction hob and underfloor heating. Before building starts, check that the consumer unit has space and suitable RCD protection, and that the main fuse can cope. Our guides to fuseboard replacement and main fuse capacity explain what to look for.

Plan circuits, not just sockets

New rooms should have their own circuits rather than being wired on to the old ones. A typical rear extension might need a new socket circuit, a lighting circuit, a cooker or hob circuit and a separate circuit for underfloor heating. Joining everything to an old kitchen ring is a common fault on later EICRs.

Lighting in open plan rooms

Large open spaces need lighting in zones: bright task lighting over worktops, softer lights over the dining area, and separate switching for each. Rooflights and glazed roofs leave little ceiling space, so wall lights and pendant drops need planning before the ceiling goes up. Fire rated downlights may be needed where there is a room above. Our guide to fire rated downlights explains when.

Garden doors and outside

Bifold or sliding doors often lead to a patio that will want outdoor lights and a weatherproof socket. Running the cables during the build is far easier than chasing them in later. See our guide to outdoor and security lighting.

Timing and certificates

The electrician's first visit comes once the structure is up and before plastering. The second comes after the kitchen and finishes are in. New circuits are notifiable, and the Electrical Installation Certificate should be kept with the building control completion certificate for the extension.

Book an electrician for your extension

Energy North Ltd works with homeowners and builders across North, East and West London with City & Guilds certified electricians. See our EICR service to check the existing wiring before work starts.