Kensington architect extension in brick with wooden doors and a brick patio

What is a side return extension?

Side return extensions are a popular way of increasing the size of Victorian and Edwardian houses in London. These properties often feature an original rear extension or ‘outrigger’ behind the main house, typically of two storeys underneath a pitched roof, like this side extension we created in Barnet, London.

The rear outrigger occupies only part of the width of the plot to allow light into the rear reception rooms in the main part of the house. This creates a leftover space, a narrow and shaded part of the garden that is usually hard paved and under-used. A side return extension encloses this space and typically creates a new party wall along the boundary with the neighbouring house.

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Heart of the home

The new volume is often joined as one by inserting steel beams, allowing removal of the original side wall. The kitchen can, therefore, widen to become a generous space. It can be further enhanced by a glass box or glass sliding doors to the rear, creating improved views of the garden.

This can transform the kitchen into the social heart of the home.


Creating vertical space

Rear outriggers were originally designed to contain service spaces and typically have lower ceiling heights than the principal rooms of the house. These can be improved by lowering the kitchen floor by one or two steps to create a more generous volume. Alternatively, inventive double-height spaces or set back mezzanines can be creating by removing some or all of the floor above. These approaches create dramatic vertical space, something that is often missing from terraced properties.

Shared wall issues

Roof heights on the shared boundary wall are frequently limited for side return extensions. Local planning policy usually restricts these heights to reduce any impact on the neighbouring house, in terms of daylight and sense of enclosure. The particular requirements vary from borough to borough, yet they are usually set out in a residential design guide supplementary planning document.


A skylight or even open light well is best placed to the rear of the new side return extension, this will allow as much natural light as possible in the original rear reception room.

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Images: rear and side return extension to a house in North Kensington

Project architect: Tom Dawson