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Side return extension costs explained

A side return extension utilises the small area of space running down the side of your property, and is an excellent way to make good use of this - often empty - area! This option appeals to homeowners wanting to increase their living space without eating in to the garden. Side return extension costs start anywhere from £35,000 to £85,000 depending on the size of the space available and the complexity of the design.

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What is a side return extension?

The side return of your home is the narrow strip of land running down one side. Depending on the size of your property, some homes use this as a lean-to or storage area, but very often it serves no useful purpose.

A side return conversion creates an extension to utilise this space and can be one or two stories, and either a standalone room or an extension to the existing rooms within your interior.

Using this space can make a huge difference in the size of your rooms and internal layout. This is an ideal choice for properties where you have a small garden, or do not wish to compromise on the amount of outdoor space you have, but wish to create more living space inside.

Sometimes a side return extension is incorporated into a single-storey rear extension as a wraparound, which makes the project more cost-effective and is a way to expand the footprint of your extension project.

side return extension cost

What are the benefits of a side return extension?

The biggest limitation factors on designing a new extension are how much space you have available to build on, and the budget in place. A side return offers a simple way to expand your living space, whether to accommodate a growing family, extend an existing room, or incorporate a new room such as a home office.

This option is flexible in terms of use, and can add to the value of your property without needing to have an impact on your existing interior should you wish to keep the layout the same.

One of the biggest benefits to extending on your side return is the use of space, adding an extra room to your home without reducing the outside space available. Most side returns on semi-detached homes are not large enough to serve any other purpose, so this is a smart way to put that area to good use.

Many side return conversions are used to extend kitchen areas, as in most period properties these tend to be small in modern terms and be a room located towards the rear of your home.

What are side return extensions used for?

Depending on the size of your home, the side return typically isn’t a huge space. However, maximising your property floor space can have a significant impact on your living area.

Common uses of a side return extension include:

  • Home office
  • Playroom or children’s area
  • Expansion of your living room
  • Extension to your kitchen
  • Addition of a dining area next to your kitchen

 This type of extension is completely flexible, and you could choose to knock through interior walls to incorporate your new space into a larger room, create an open plan area with your new footprint, or use it as a separate room.

Side return extensions can be included in part of a larger extension project, either as part of a wraparound, in addition to a single-storey extension or can be a standalone project.

How much does a side return conversion cost?

The reason that budgets for side return conversions vary so much is that they can be very different in terms of the build time and design process, since your extension is tailored to fit your home and the space available.

Side return extensions can cost between £35,000 to £85,000 and will add between 10-20% to the value of your property depending on the size and standard of the conversion.

How can you keep your side return extension cost down?

There are a few ways to keep the cost of your extension to budget, and decisions that will impact the overall cost:

  • Opt for standard size windows, or minimise the amount of large glazing since custom made glass is an expensive option
  • Choose to complete your extension in phases, to effectively budget for each stage and break down the costs
  • If you are extending your kitchen, buy your units separately or avoid designing an excessive number of units since joinery will add costs to your budget
  • Select a living space rather than a bathroom since the plumbing costs will drive up the project total
  • Research different materials and finishes to meet your design aspirations but which are cost-effective
  • Shop around for professional services, contractors and architects to ensure you are getting the best deal

If you are completing your side return extension in one go, make sure that your contractor agreements are clear, have set timescales, and specify exactly what works, materials and finishes are included within the cost.

Cost factors to building a side return conversion:

Since side returns are so flexible, the costs are very much dependant on your design and build process, as this will be unique to your home. Considerations to bear in mind include:

Works required to adjoining rooms.
If, for example, you are creating a side extension to expand the size of your kitchen, there will be additional costs for work and fitting in the existing room, as well as construct the new extension.

Your intended purpose of the new space.
Kitchens and bathrooms are always more expensive than living areas since there are extra costs involved to purchase units, fit utility supplies and install appliances.

The scope of the extension.
If your side return is part of a larger extension, or is the side wing of a wraparound extension, the costs will be higher – but the cost per m2 is likely to be lower for a larger footprint.

Glazing requirements
Doors, windows, frames and finishes can add cost to an extension, so decide on how much glazing you would like, and be sure to incorporate the costs for custom frames and glass into your budget.

Specific finishes for luxury extensions will also ramp up the budget, for interiors such as polished concrete floors or large custom-fitted doors.

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Side Return Extension Cost Frequently asked questions

How long does it take to build a side return extension?

Typically, a side return conversion takes around three to four months to complete. This does not include the time required for any planning permissions or the design process.

Including the design, fitting, build process and planning, it is best to allow around six months for the project, which will decrease if planning is not required and depending on the complexity of the design.

Check with your builder before any work starts what the timeframe looks like to ensure you both have an agreement on the expected completion date. This will allow you to make sure that the extension build is running to schedule, and plan for using your new room!

Do I need planning permission?

Some extensions require planning permission, and others do not – it all depends on the size of your existing property, how large your extension will be, and how this impacts the borders of your land between you and your neighbours.

If your extension falls within a set of criteria, no planning permission is needed. However, side returns are more likely to require permission since they will very often build up to the edge of your party wall and require an agreement in advance.

Given the tendency of these extensions to be fairly compact, unless you have had previous additions added to your home, a side return conversion will usually fall within the maximum build space allowed under Permitted Development (PD – which does not require planning permission) but it is always advisable to contact your local planning authority in advance to make sure you know whether to apply.

Should your home be a Listed Property, or be a Victorian premise in a conservation area, then you will require permission even if the size of the extension does fall within PD perimeters.

If in any doubt, it is worth spending a little time and a small fee to ask your local authority for pre-planning advice, which will confirm in writing where you stand.

What are the build stages of a side return extension?

Stage 1: Constructing the new exterior walls
First, the new walls that will create the boundary of your extended property will be built.

Depending on the design of your conversion, these may be load-bearing walls and will, therefore, require foundations to be dug and concrete to be poured to stabilise the structure before the building work begins.

Stage 2: Roofing is added
Usually, the roof is added next, to protect from the elements before any of the existing walls are removed. Choosing a glazed roof or a large skylight is a popular choice to maximise the natural light within your home, but is a more expensive option.

You will have decided at the design stage whether to replicate the existing roofing of your home, opt for a modern exterior, or choose a new material.

Stage 3: Existing walls are knocked down
When your existing walls are removed your contractor may need to erect a steel frame into the wall space, to support the new opening and ensure the structure is robust. The wall might need to be removed completely, or some of it removed depending on how your existing interior blends with the extension.

If you plan to use your new conversion as a standalone room, you could opt not to remove the walls in their entirety, but this does offer a better way to maximise space by replacing them with thinner internal walls.

Stage 4: Flooring is laid and any remaining glazing installed
Usually, your flooring will begin with concrete being poured to level off the floor and ensure this sits on the same level flush with the existing flooring inside your home.

Once this has dried, the finished floor covering can be applied. If your glazing was not installed at the same time as the roofing, this will now be added.

Stage 5: Decorating

Once the building works have completed, the fit-out can begin. This usually involves a few stages with tradespeople fitting utility supplies such as electrical outlets, before decorative work behinds.

What are the drawbacks to a side return extension?

One of the most typical properties to benefit from a side conversion is a period property. Many such properties are terraced or semi-detached and were designed with a side space which is difficult to find a good use for.

What this does mean is that your side return may not provide the best position for natural light, particularly if it will sit flush with the adjacent property. Check out the lighting in your side return during different times of the day to understand how bright space is, and when it most benefits from sunlight.

To increase the light in your home, you can choose to install Velux windows, use a glazed roof or glazed panels, or select a pitched roof design to bring in as much sunlight as possible.

What does the Party Wall Act mean for side return conversions?

The Party Wall Act requires you to advise your neighbours in advance if you plan to carry out building work that will be against your shared boundary, or very close to it. This notice should be a minimum of two months before work starts, and can be up to a year in advance.

Your neighbour(s) have two weeks to consider the extension you have in mind and respond in writing. If your neighbour isn’t happy with your plans, then it may be necessary to appoint a surveyor to draw up a party wall agreement between the respective homeowners.

This can add a cost to your budget since usually the owner who intends to carry out the building work will be expected to cover the costs, so having an informal chat with your neighbour before you put any plans in motion is the best way to make sure you have paved the way for a smooth build process.

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