Side-return extensions on Victorian and Edwardian terraces

Most Victorian and Edwardian terraces have a narrow strip of outdoor space running alongside the back addition, the side return. Filling it in is one of the most effective ways to turn a long, narrow galley kitchen into a wide kitchen-diner, which is why side-return extensions are so common across South West London. This guide explains the options, how planning works, and the practical details that make the difference between a dark corridor and a bright, useful room.

What a side return is

A typical period terrace has a main house at the front and a narrower two-storey back addition, sometimes called an outrigger, behind it, usually containing the kitchen with a bathroom above. Because the back addition is narrower than the house, it leaves a passage between its side wall and the boundary with the neighbour. That passage is the side return. It is often only a metre or two wide, gets little sun and ends up as a storage space for bins and bikes.

Streets like the grid in Southfields, the Victorian terraces of Earlsfield and Colliers Wood, and much of Fulham are made up almost entirely of houses like this, so the side return is one of the most common opportunities in the area.

Side infill or wraparound?

A side-return infill fills the passage alongside the back addition, with the extension's outer wall on or near the boundary. It widens the existing kitchen without changing the length of the house or eating into the garden.

A wraparound extension combines a side infill with a rear extension, wrapping around the end of the back addition in an L-shape. It creates a much larger open-plan space, often a kitchen, dining and living area across the full width of the house, but it takes more of the garden and is a bigger project for planning, cost and time.

Planning permission

At the time of writing, a single-storey side-return infill can often be built under permitted development, provided it stays within the national limits for side extensions, including a maximum height of 4 metres, a width of no more than half the original house and materials similar to the existing ones. Wraparound extensions, which combine side and rear elements, usually need planning permission. Permitted development does not apply to flats, and side extensions are not permitted development in conservation areas. Check the current rules on the Planning Portal, and consider a Lawful Development Certificate for a permitted development scheme.

Where permission is needed, councils pay close attention to the height of the wall on the boundary, because that is what the neighbour sees. Hammersmith & Fulham's guidance limits extensions alongside the back addition to 2 metres high on the boundary, with a roof sloping at no more than 45 degrees. Richmond's guidance asks for side infills on Victorian houses that go deeper than usual to keep a low eaves height, which is relevant to the cottages and terraces of Barnes. Wandsworth's Local Plan asks that side infills do not create a terraced effect. Designing to these limits from the start makes approval far more likely.

The boundary wall and your neighbours

Because a side-return extension sits on or beside the boundary, it almost always involves the Party Wall etc. Act 1996, either because the new wall is built at the line of junction between the two properties or because new foundations are dug close to the neighbour's. You need to serve notice before work starts. Our guide to the Party Wall Act explains the process.

Many neighbours will be considering the same extension, or will already have done it. Where both houses fill their side returns, a single shared wall on the boundary can serve both extensions, which is worth discussing with the neighbour early.

Light: the most important design decision

The main risk with a side-return extension is darkness. Filling the passage removes the window that lit the kitchen from the side, and the middle room of the house, often the dining room, can lose daylight too. The answer is to bring light in from above. Most side-return extensions have a glazed or partly glazed roof over the infilled section, or large roof lights, so daylight falls into the centre of the new room.

The roof design needs to balance light, heat and privacy. Fully glazed roofs are dramatic but can overheat in summer and need good solar-control glass. A solid roof with a long strip of roof glazing along the boundary, or a series of roof lights, is often a more comfortable compromise, and it can be easier to get through planning where the boundary height is limited.

Structure

To make one room out of the old kitchen and the new side extension, the side wall of the back addition has to come out. Because that wall supports the floor and bathroom above, it is replaced with steel beams, designed by a structural engineer, which carry the load down to new supports. Building Regulations approval covers this, together with the foundations, insulation, drainage and ventilation of the new space.

Drains and soil pipes

Side returns are where period houses tend to hide their drainage: soil stacks from the bathroom above, rainwater pipes and underground drains often run along the passage. These usually need to be rerouted or boxed in, and manholes may need to be moved or fitted with sealed covers inside the new room. If the extension will be built over or close to a public sewer, the water company usually needs to approve it through a build-over agreement before work starts, so it is worth tracing the drains at the survey stage.

Keeping the character of the street

Side-return extensions are at the back of the house, so they rarely affect the street directly, but the rear of a terrace is still part of its character, especially in conservation areas. Brick that matches the house, a roof form that sits below the first-floor windows, and details that respect the original back addition all help an extension look as though it belongs. Our house extensions page explains how we approach design and approvals, and our kitchens page covers fitting the new kitchen that usually follows.

Living with the work

The kitchen is out of action for much of a side-return project, so most families set up a temporary kitchen elsewhere in the house. The back of the house is opened up when the side wall comes out, and the build is planned so the house stays secure and weathertight throughout. A written programme agreed at the start makes it clear which rooms are affected and for how long.