A single storey rear extension is the simplest way to add a larger kitchen or family room and suits most houses with a reasonable garden. A side return extension fills the narrow strip beside a terraced or semi-detached house and is ideal for widening a cramped kitchen. A wrap-around combines the two for the biggest ground-floor change, at the cost of more complexity. A two storey extension adds space on both floors and is the choice when you need another bedroom. The right one depends on your house, your plot and what you want the space to do.
Single storey rear extension
Built across all or part of the back of the house, a single storey rear extension is the most common type we see. It typically creates an open-plan kitchen, dining and family space with doors on to the garden. The structure is straightforward: foundations, walls, a flat or pitched roof and a new opening into the existing house, usually supported by a steel beam.
Many rear extensions can be built under permitted development if they stay within size limits and the house still has those rights. The main trade-off is garden space, and the middle of the house can become darker if the extension is deep and has no roof glazing.
Side return extension
Many Victorian and Edwardian terraces have a narrow outrigger at the back with a thin alley of outdoor space beside it, known as the side return. Building into that strip widens the kitchen, often transforming a galley into a room that can take a table. Because the gap is usually small, a glazed or partly glazed roof is common to keep light flowing into the house.
Side returns often involve the boundary with a neighbour, so the party wall process is frequently part of the project. Our guide to party wall agreements explains what that involves.
Wrap-around extension
A wrap-around, sometimes called an L-shaped extension, combines a side return with a rear extension. It produces the largest change on the ground floor, often a single broad room across the back and side of the house. It also brings more corners, roof junctions and steelwork, which makes design and building more involved than either type on its own.
Wrap-arounds usually need a full planning application rather than permitted development, because the side and rear elements together exceed the simpler limits.
Two storey extension
When you need more bedrooms or a bigger bathroom as well as ground-floor space, a two storey extension adds both at once. It can go to the side or rear depending on the plot. Foundations and roof are shared across two floors, so the extra floor area is efficient, but the design must consider neighbours' light and privacy, the staircase layout and how the new roof meets the old.
Most two storey extensions need planning permission, and the council will look closely at their effect on the street and adjoining houses.
Comparing the options
This table gives a general comparison. Every house is different, so treat it as a starting point for discussion. The planning routes are explained fully in our extension planning permission guide.
| Type | Suits | Light | Layout change | Complexity | Usual planning route |
|---|---|---|---|---|---|
| Single storey rear | Most houses with a garden | Good at the back; roof glazing helps the middle | Bigger kitchen or family room | Lower | Often permitted development |
| Side return | Terraces and some semis | Glazed roof keeps the house bright | Wider kitchen | Moderate; often involves a boundary | Varies; check with the council |
| Wrap-around | Terraces and semis wanting maximum ground floor space | Needs careful glazing | Largest ground floor change | Higher | Usually full planning |
| Two storey | Homes needing extra bedrooms | Can affect neighbours | Space on both floors | Higher | Usually full planning |
Choosing for your house and garden
Start with what you want to use the space for, then look at the house. A terrace with a side return lends itself to infilling; a detached house with a wide plot may suit a side or rear extension; a growing family short of bedrooms will probably need two storeys. Think about how much garden you are willing to give up and where the sun falls, because that decides where glazing will do the most good.
Cost depends on size, structure, glazing and finish rather than the label, and our house extension cost guide explains the drivers in detail. When you are ready to talk about building, our home extensions page explains how Superior Build & Landscape approaches single and two storey projects.
Frequently asked questions
What is a side return extension?
It fills the narrow strip of outdoor space beside the back part of a terraced or semi-detached house, usually to widen the kitchen.
Is a wrap-around extension worth it?
It gives the largest ground-floor space of any single storey option, but it is more complex to design, approve and build. Whether it is worth it depends on how you want to use the room and your budget.
Which extension adds the most usable space?
A two storey extension adds space on both floors. On the ground floor alone, a wrap-around usually adds the most.
Can a rear extension be built under permitted development?
Often, if it stays within size and height limits and your home still has permitted development rights. Conservation areas, flats and some newer estates are exceptions.
How long does an extension take to build?
It depends on the size, structure, ground conditions, weather and how much finishing work is included. Simpler single storey designs are quicker than wrap-around or two storey projects, and George will explain the order of work when he quotes.