A Side Return extension

Revive and extend an older property by using an often overlooked and underutilised area of your plot – your side return.  

Did you know?  That space at the side of our house – the one that’s currently storing bikes and bins – could hold the secret to transforming the ground floor, giving you ample light and room to create your dream family or party zone. Side-return extensions usually fall under permitted development (PD), and are an impactful way to maximise the floorplan.  Extending out by just one metre could expand a galley kitchen into a kitchen-diner or allow you to create new areas, such as a utility or WC, while reconfiguring the layout for a more open-plan space. 

A side-return extension is the perfect opportunity to incorporate glazed elevations and roof windows to bring more natural light flooding in and make it feel even roomier.  The new addition could also improve your home’s connection to the garden.

Many period properties have benefitted from this type of extension.  Read on to find out how your home can too by expanding into the side return. 


  • Building Regulations – a set of standards that should be adhered to when renovating or building a new property
  • Planning Permission – a request made to the local council to carry out building works on your property or garden
  • Permitted Development – works that can be undertaken on a property or garden without needing planning permission
  • Party Wall – a shared border fence, wall or hedge that separates two adjoining buildings.  Built on the boundary line, it demarcates ownership
  • Conservation Area – an area of land of special architectural or historical important
  • Solar Gain – a temperature increase caused by heat from the sun through glazing

Planning Layout

You may already know where your favourite sofa will sit, the bookshelf installed and the family heirloom placed, but how many of an impact will these have on the positioning of electrics for lighting and pipework for plumbing?  Speak to your designer or builder about whether the island will run parallel to the rear wall or whether the dining table will sit under the rooflights.  All these decisions will ultimately lead to smaller questions – so its best to have a clear idea from the start. 

TOP TIP * Access all Areas

Building to the side of your property can cause access issues during construction, especially one you’ve extended into the side return and closed off entry there.  Consider how you’ll get machinery and materials to the rear.  Could you order everything earlier and store it in the garden before work starts?  Craning items in is an option, but an expensive one – and hauling large items through the property could cause damage if you’ve already had work completely internally.

Modern Finish

The kitchen at the heart of this home didn’t work with the rest of the layout.  Location in the middle of the plan, its L-spade configuration made everyone walk through it and feel on top of each other.

‘The owners were keen to bring a bright feel to the ground floor space and to give it the best chance of being used well,’ says James Bernard, director of Plus Rooms. ‘We put in a glass valley to achieve this, which is a detail that changes the angle on the roof and maximises light into the back reception. They also really wanted to appreciate their garden, because the only had a very limited opportunity to do so with the existing layout. They didn’t want to do it up before the works because they knew that any investment outside would be wasted, so they halted their overhaul until after building finished.

‘The project was scheduled to take eight weeks plus finishing, but construction was completed within seven even though we had some challenges when dealing with the neighbour on party wall matters.  We liaised with them and the clients throughout to share detailed information, explained that we were doing, and, eventually, the works could proceed.  The home’s foundations also needed to be reinforced.  We do a detailed survey prior to work starting, and we found this out early on – which meant this was factored into the budget from the outset.  The owners chose to have a concrete floor, which was not included in the original quote and that increased costs slightly.  Otherwise they were able to enter the build knowing exactly what to expect regarding costs.

‘I’d advise renovators who have a similar set up and are planning on extending, and have a bathroom that sits directly above the kitchen, to wait until after the building work downstairs is complete before renovating it.  There may be shifting during construction, which would be counterproductive, as no-one wants hairline cracks in their newly renovated bathroom.  Although the kitchen is in the same location as before, the new 12-metre square side extension has allowed the ground floor to lose its unpractical format.’

Before you Start – Q&A

  • How long will it take?  Between eight and ten weeks to build
  • How much does it cost?  We’d recommend budgeting from around £1,500 to £1,900 per square metre for a basic quality extension.  Architectural service Resi suggests that the average build cost for a side or rear extension, excluding VAT, could cost from around £67,500 in London, or £55,688 in the rest of the UK.
  • Do I need to get permission?  It’s worth noting that applying for consent can help you get a more creative design – but if you only want something basic, a side return extension usually comes under permitted development as long as:
    – you’re not extending onto designated land;
    – no more than half the land around the original house is covered by additions or other buildings;
    – the exterior finishes are similar to those of the existing house;
    – It isn’t more than half the width of the original house;
    – extensions are no more than six metres beyond the rear wall of the house (eight for a detached);
    – it’s no more than four metres high (or three if it’s within two metres of the boundary);
    – you’re not living in a listed building or Conservation Area.

Period Properties

When renovating and extending an older property, it’s worth deciding whether you want remain sympatric to the existing style and blend the new in or venture away from that aesthetic by adding something distinctive.

This applied to glazing too; bi-fold and sliding doors are contemporary additions that can feel at odds to traditional designs, while Crittall-style aluminium doors tend to look good on Victorian and new-build properties alike. 

If your building is listed or locations in a Conservation Area, you may be limited in the style that you can apply for, so it’s worth speaking to the local council and seeking pre-application advice before you get underway.  There are often compromises to be made, such as losing a chimney in order to move a wall or add more room; you’ll have to weight up what’s important early on to stay on budget and on schedule.

TOP TIP * Roof Design

From contemporary flat roof designs with room for a sustainable green roof to pitched options that replicate an existing roofline and lowers the risk of standing water, providing you’re not in a listed property, your roof options could be quite varied.  Modern options today also include curbed and sawtooth designs that allow light to penetrate deep into the plan.


When it comes to the flooring, think not only how the covering will complement the internal scheme and work with underfloor heating, for instance, but also how it can help create a connection with the exterior space.  If you choose the same material for both areas, make sure you se the non-slip surface suitable for outside.


Project cost – approximately £70,000

Designer – Plus Rooms  0800 917 7127  www.plusrooms.com 

Construction time – seven weeks

TOP TIP * Party Walls

More often than not this is a fairly straightforward process of giving your neighbour prior notice of a minimum of two months, to which they have 14 days to ‘assent’ or ‘dissent’. It’s worth speaking to them in advance to explain what works you’re carrying out and how it might affect them. If they agree, you’re fine to go ahead.; if not, you’ll need an impartial party wall surveyor to follow the works, of you can each hire your own.

Clever glazing

An extension is the perfect opportunity to increas the amount of natural light and mazimise the level of brighness entering the ground floor, especially if your addition puts the middle of the house in the dark. Choosing optimal glazing and window placements can effectively transform a gloomy interior space. No matter what your budget is, you can add some form of a rear glazed façade using fixed panes and sets of patio or sliding doors.

If you can’t afford a fully glazed roof to help filter light deeper into the plan, consider fitting a mix of affordable openable and fixed rooflights. Adding clerestory windows could also be an option for top-down light. The glazing doesn’t have to be fancy, but functionality here is essential – make sure you’ve thought about how you’ll ventilate the space and avoid having too much heat loss in the winter or too much passive solar gain in the summer months.