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Side Return Extensions: Expert Guide to Nailing the Design

A side return extension
(Image credit: YARD Architects / Agnese Sanvito)

It's not surprising that side return extensions are on of the most common residential build projects homeowners choose to do. The side return extension is a fantastic way to kick out the footprint of terraced houses and semi-detached homes. 

Dealing with often narrow side returns and with it restricted access, the design of a side return extension has to be thought through properly. 

It's got to work with the existing house to make sure the light, the flow and the quality of the spaces work together and improve what you have.

Get the fundamentals right and you'll create a space that'll stand the test of time.

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Should a Side Return Extension Match the Existing House?

Complementary or contrasting? Both work well and while there are no hard and fast rules, the best approach is to think about the kind of new space you want from your extension.

If you are trying to radically alter your interior space, knocking down walls and making big openings for inside/outside living, then clearly this is very different from the existing space in an old terrace. If you are doing this then I think you should contrast the design, expressing a new stage in the building’s life.

If however you are proposing smaller French doors and maintaining (but subtly altering) the existing layout, then a more sympathetic ‘in keeping’ design can work.

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side return extension for a kitchen

This side return extension designed by The Gentleman Architect has created a much wider kitchen diner for this terraced property. A glazed roof and clerestory window flood light down into the whole room. (Image credit: The Gentleman Architect / Juliet Murphy Photography)

How to Bring Light into A Side Return Extension

Introducing light into the whole house – not just to the new extension but to the hallway and the heart of the floorplan – is a key element of a successful side return extension. Being creative with light deeper in the building is critical to this too, as this project below goes to show.

side return kitchen extension

A glazed door and roof were a big part of the design for this side return extension designed by YARD Architects to allow light deep into the floorplan. (Image credit: YARD Architects / Agnese Sanvito)

Doing away with the separate kitchen by infilling the narrow strip of the garden adjacent to the house and squaring off the floorplan to create a larger kitchen dining room makes a lot of sense.

It is often the only possible way of extending the house, but in doing so you can create new space at the expense of daylight penetrating the middle of the house. A large part of the genius of the terraced house design is that the only area that doesn’t usually get good daylight is the stairs.

Putting on a side return extension can plunge one of the main rooms into darkness, making it far less usable — you will need to be creative with rooflights, ceiling levels and artificial light to keep the quality of space.

One option is to embrace the dark and create an intimate internal room for the evenings that is the Yin to the bright kitchen diner’s Yang, or an alternative is to move toilets and utilities – rooms that do not need so much natural light – to the centre of the house.

Contemporary kitchen in London terrace house extension

This London terrace house extension features narrow roof lights, an internal window and bifold doors to maximise natural lights in other areas (Image credit: Jeremy Phillips)

Consider Ceiling Heights in a Side Return Extension

A side return extension nearly always requires walls to be knocked down and there is always a temptation to take the easy route when doing this and simply put a steel beam under the joists of the existing floor above to support the rest of the building.

This structure is then boxed in to create what the trade calls a ‘downstand’ — learn the name and learn to avoid it at all costs. This is because even though the wall has gone, the residual downstand has a big impact on creating the feeling of a new large single room. It divides the room, stops space flowing and makes the ceiling feel low and heavy.

If you have very high ceilings you can design your way around a downstand. But for nearly all situations, go to the extra expense of pushing the new structure into the depth of the floor above and losing it. If you have to cut back on the cost of the kitchen and fit out, do so, as this can be easily improved at a later date — fiddling with the structure can’t.

side return extension

Designed by Syte Architects, this single-storey side return extension added to this London terrace stitches to the existing building via a band of glass that runs up and over the roof. (Image credit: Syte Architects / James Morris)

To increase the sense of space in your new side return extension, try and create taller and/or vaulted ceiling heights in the new area that contrast with the old. This will draw the eye upwards and make even a small increase in space feel much larger.

Creating extra volume and height in the new space is a clever way of making it feel more dramatic. It’s only really practical in single storey extensions, but a 3m ceiling height can make a big difference

Removing the external wall usually involves adding in a steel beam to support the wall and floor above. Where possible, try and avoid a downstand as it can separate out the space and affect ceiling heights. The example above integrates the new space more effectively, with a bolder design.

Extension plays with different ceiling heights

This extension by Coffey Architects plays with different ceiling heights to make the space feel larger (Image credit: Coffey Architects)

Think About Moving Plumbing When Adding a Side Return Extension

Often the rear courtyard of the terrace has, over the years of retrofit and upgrading, become something of a spaghetti junction of services and plumbing. There are often manholes, waste downpipes, rainwater downpipes, etc.

One of the first jobs in designing your scheme is to get a handle on how you are going to adapt the plumbing to allow for your new extension to shine. The alternative is boxed-in downpipes squeezing already narrow spaces, big ugly removable manhole covers smack bang in the middle of a new floor, and ugly waste pipes snaking around the roof of your pride and joy — I have seen it all.

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