Side return extensions, built into that slender strip of outside space that runs alongside the rear part of many a terraced or semi-detached house, offers extension potential out of all proportion to its size. As a garden space, these side return extensions often aren’t well used and don't add value to your home. But build a single storey extension into one and it can transform your existing, perhaps narrow, back room into one that's spacious and light-filled, making space for a generous kitchen, dining room and living area.
It's a relatively inexpensive form of extension, too, and although some garden space is inevitably sacrificed, a good side-return extension can improve the indoor-outdoor connection.
Use this guide to planning and designing a single storey extension to get yours right – then hop to our ultimate guide to extending a house for all the practical advice and inspiration you'll need.
1. What type of side return extension will you build?
Building a single storey extension is the cheapest and often most viable option. Frequently built as a kitchen extension to turn a small kitchen into a generous, open-plan kitchen-diner, such an addition can help provide garden-facing dining and seating, or the extra width could even contribute to a reconsidered, more open-plan layout throughout the ground floor.
Two storey extensions can be possible, too, and although one of these will cost you more to build than a single storey one, it will be more cost-effective to build – in other words, you get more square footage for your money.
2. What does a side extension cost?
If you're planning a side return extension, the best place to start with costing is our free extension cost calculator, which will give you a good idea for budgeting. However, for a rough idea, expect to pay the following build costs only on a single storey addition:
- around £1,500 to £1,900 per square metre for an extension of basic quality;
- around £1,900 to £2,200 per square metre for a finish of good quality;
- between £2,200 to £2,400 per square metre for a finish of excellent quality.
Our ultimate guide to extending a house has full costing details. Bear in mind that you'll pay more for materials and labour in some parts of the country than others.
3. Can I build a side return extension without planning permission?
You probably won’t need planning permission for a side return extension. The current permitted development regime allows single-storey side extensions up to a maximum of 4m high and a width no more than half that of the original house. If the extension is within 2m of the boundary, eaves height should not exceed 3m.
However, if you live in a Conservation Area, national park, AONB or there’s an Article 4 direction on your property, you may need to get planning permission, so check with your local authority. Find out more with our guide to planning permission and to building a single storey extension without planning permission.
4. How can I reflect light into the depths of the extension?
Clever colour scheming can help compensate for the loss of the side window and increased depth to the room when you extend into a side return. Pale kitchen cabinetry, reflective materials, glass or high gloss tiled splashbacks and pale stone flooring will all help bounce light around. Introduce warmth with wood finishes, or taps and pendant lights in copper or brass.
5. Letting in light (and views) with glazing is a must
Rooflights link a side-return extension to the outside, especially when tall trees are visible in the surroundings, and a view of open sky can also help the interior feel bigger. A window with minimal framing and no glazing bars across it will maximise sightlines, particularly if it’s floor to ceiling, as will sliding doors or large leaf bi-folds with the same barely-there style of frame.
6. Plan the room layout as you design the extension
Your kitchen extension design goes hand-in-hand with designing and planning the kitchen. The extra width of the new room is often used to add a dining table, creating an eat-in kitchen. The former side return can be a good location for the table, with a long run of units on the opposite wall. With sufficient width, a kitchen island can separate kitchen and dining space, introducing an extra preparation surface and perhaps a breakfast bar.
Alternatively, an L-shaped kitchen at the back of the new space could allow the dining table to be placed centrally in the room and further towards doors to the garden.
7. Roof windows don't need to open – which will save £££s
Should rooflights in the side return extension be openable? If your bi-fold, sliding or other patio doors are likely to be open as often as possible, then you may not need to be able to open the roof windows to ventilate the room, so can make a saving – fixed designs are usually more budget-friendly.
8. Put the dark end of the room to good use
Extending to the side can make the middle of the house dark. Use rooflights to bring daylight in. Bi-fold or sliding doors to the garden could be fitted across the back of the room you are extending, or combine slimmer versions with large windows. Consider placing a room that doesn’t need daylight, like a utility, cloakroom or storage, at the centre of the house.
9. Keeping neighbours on-side can save you £££s
If you’re working on the existing party wall, building a new one at or on the boundary line with next door, or excavating near an adjoining building, you’ll need a written party wall agreement from next door before work begins. Start by serving a party wall notice on the neighbours, or pay a party wall surveyor to do this on your behalf.
Better still, keep them informed of your plans from early on and see if they'll agree to sign a party wall agreement waiver – doing so will save you at least £1,000.
10. Dealing with the openings into the new room
You may be left with two openings to the new room: the original from the hallway, and a second where a reception room window used to be when it overlooked the side return. If so, a bank of kitchen cabinetry – possibly including a fridge-freezer – can be an effective use of the wall space in between. Alternatively, why not include open shelving or a mixture of shelves and closable units? This is where good kitchen planning comes in.
11. Replace all the downstairs flooring
A continuous floor finish throughout will help the new side return extension feel as large as possible. You could even opt for the same flooring in the front reception rooms and hall to create a fuss-free look and expansive feel across the ground floor. If you take the latter option, bear in mind that what you choose needs to stand up to foot traffic throughout, be easy to maintain and suitable for all of the individual zones.
12. Add character without breaking the budget
Architectural details can drive up your costs, so if you're extending on a budget, you might want to look for ways of saving money. You may want to keep wall finishes the same in the newly extended space, but a different look for the wall of the side return can make the room look less boxy.
Exposed brickwork or brick slips can add an industrial touch. A patterned or textured wallpaper can create contrast. Easier still is to paint the side-return wall a different colour from the rest of the room.
13. Plan thoroughfares to make the kitchen work
It’s important that your side return extension doesn’t result in the working part of the kitchen becoming a passageway. A central kitchen island can be a sensible way to divide the preparation and cooking area from the route into the new room from the front of the house. A peninsular kitchen design is also a handy way to direct foot traffic.
14. Choose doors to have a major design impact
Sliding or bi-fold doors with minimal framing opening to the garden are definite winners, but using a more traditional door style can make a new side-return extension feel at one with a period property.
Or consider industrial-style steel-framed windows and doors that will provide snapshot views to the garden. A design like this can harmonise beautifully with an exposed brick wall, or industrial details in a kitchen.
15. The roof design should echo your home's architecture
A single pitch roof can make a side return feel loftier inside, and look attractive viewed from the garden. But, flat glazed roofs or one with a series of rooflights, can be equally as effective. Pitched roofs have a more traditional appearance, while a flat roof can appear sleeker. The latter is also worth considering as a good way to focus light on a dining area.
16. Consider the exterior finishes early
Should a side-return extension match or contrast with the original house? Both are possible – and can be successful. Matching materials will create a harmonious feel, whereas contrasting contemporary finishes make the new addition overt. Call on an architect to help with your plans – and check out our feature on transforming your home's exterior for inspiration.
17. Being space efficient will make it feel roomier
If the new room is still of relatively modest proportions once the side return is incorporated into the interior, a single line galley kitchen can provide functional cooking and preparation areas. In this scenario, too many wall units can be oppressive, so plan in shelving or glass-fronted units to keep the feel open. Make sure there’s worktop space either side of the hob as well.