Types of Home Extension Compared

Rear, side-return, wraparound, single or double storey, or built over an existing structure. Before you can talk about cost or planning, you need to know which shape of extension actually fits your house and the way you want to live in it.

When people say they want a "home extension" they usually have a feeling rather than a plan, more light, a bigger kitchen, an extra bedroom, somewhere for the family to spread out. The job of a good builder is to turn that feeling into the right footprint. And footprint is the word that matters, because the type of extension is really a question of which direction you build in: backwards into the garden, sideways into a passage, around a corner, or upwards over part of the house you already own.

This guide walks through the main types of extension we build across Aberdeen and Aberdeenshire, what each one is good at, and the kind of home each tends to suit. By the end you should be able to picture which one or two options are worth costing for your property before you book a home extension survey. If budget is your first question, you may prefer to start with our home extension cost guide and come back here.

Extensions by direction, not just by name

It helps to stop thinking about extensions as a fixed menu and start thinking about the three directions you can add space. You can go out at the back, you can go across to the side, or you can go up over something already there. Most real projects are a sensible combination of those, and the names below are simply the common patterns those directions fall into. Keep that in mind as you read, because the right answer for your home is often a blend rather than a single labelled product.

The rear extension

A rear extension projects out from the back of the house into the garden. It is the most common type we build, and for good reason. The back of a house is usually where the kitchen and the main living space already sit, so extending there lets you open up a larger, brighter, better connected ground floor without disturbing the front elevation or the street view at all.

A single-storey rear extension is the classic way to create an open-plan kitchen and dining space, especially when it is fitted with large glazed doors and a roof lantern to pull in light from above. Because nothing is built upwards, the structure and the planning position are usually straightforward, which keeps both the timeline and the cost sensible. If a bigger, brighter kitchen is the real goal, our kitchen extension ideas guide shows how a rear extension and a new kitchen are usually designed as one project.

Best for: homes with usable garden depth at the rear who want a larger ground floor, more natural light, and an open-plan kitchen-diner.

The side-return extension

Many older and terraced homes have a narrow, awkward strip of land running down one side of the back of the house, often where the original kitchen wall steps in. That strip is the "side return". It is frequently wasted, used for nothing more than a path or a few bins.

A side-return extension fills that strip in, widening the existing room rather than lengthening it. It rarely adds a huge amount of floor area on its own, but the effect is out of all proportion to the size, because it squares off a cramped galley kitchen into a proper, full-width room and floods it with light from a new run of glazing or rooflights overhead. For the right house it is one of the most cost-effective changes you can make.

Best for: terraced and older semi-detached homes with a narrow side passage and a kitchen that feels long and thin.

The wraparound extension

A wraparound extension is exactly what it sounds like, a rear extension and a side-return combined so the new space wraps around the back corner of the house in an L shape. It is the most generous single-storey option, often turning the entire back of the ground floor into one large, flexible family space with room for a kitchen, a dining table and a seating area all at once.

Because it is larger and more structurally involved than either part on its own, a wraparound sits higher up the cost scale and is more likely to need planning permission rather than falling under permitted development. For families who plan to stay put and want to transform how the ground floor works, it is frequently the option that pays back most in daily living.

Single storey versus double storey

So far every option has been single storey. The moment you decide to stack a room above the new ground floor, you move into double-storey territory, and the economics change in your favour. A double-storey extension shares the most expensive parts of the build, the foundations and the roof, across two floors instead of one, so the second storey is far cheaper per square metre than the first. You typically gain a downstairs living space and an extra bedroom or bathroom above for a total cost well below building each separately.

The trade-offs are that a double-storey extension affects the look of the house more, is more likely to need planning permission, and can have a greater impact on a neighbour's light and outlook, which planners will consider. It is not automatically the right answer, but if you need bedrooms as well as living space it is usually the best value. We compare the two in full, with a worked sense of where each wins, in our dedicated guide to single versus double storey extensions.

Over-structure extensions

The fifth type often gets overlooked. An over-structure extension builds a new room on top of something that is already there, most commonly above an attached single garage or an existing single-storey extension. Done well, it is a clever way to add a bedroom or a home office without giving up a single square metre of garden, and without changing the building's footprint on the ground at all.

The catch is structural. The existing foundations and walls below were not always built to carry an extra floor, so the first job is always to check whether they can take the load or need strengthening. Where the structure stacks up, an over-garage room is one of the most space-efficient extensions there is. Where it does not, the cost of underpinning can tip the balance towards building fresh. This is exactly the kind of judgement a site survey settles quickly.

Which type suits which home?

There is no single best extension, only the best one for your house, your plot and your priorities. As a starting point:

• You want a bigger, brighter kitchen and have garden to spare: a single-storey rear extension, often paired with new kitchen units, is the natural fit.
• Your kitchen is long, thin and dark with a passage beside it: a side-return will transform it for a relatively modest spend.
• You want to remodel the whole back of the house into one family space: a wraparound gives the most open-plan floor area on one level.
• You need an extra bedroom or bathroom as well as living space: a double-storey extension is usually the best value route.
• Your garden is precious but you have a garage: an over-structure extension adds a room without losing outdoor space.

If you are weighing an extension against the cost and upheaval of moving house altogether, or against converting space you already have such as a loft or garage, it is worth reading widely before you commit. Our team works on the full range across the North East, and you can see a sense of that range on our recent projects page.

Planning permission and building warrants in Scotland

Whichever type you choose, two separate approvals can apply in Scotland, and it is worth keeping them straight. Planning permission is about whether you are allowed to build what you propose, given its size, position and effect on neighbours and the street. Many modest single-storey extensions fall within permitted development and do not need a planning application, while larger schemes, wraparounds and most double-storey extensions usually do.

A building warrant is separate and is about how the work is built, covering structure, insulation, fire safety and drainage. Almost every extension needs one, issued by Aberdeen City Council or Aberdeenshire Council, regardless of whether planning permission was required. We handle both applications for you as part of the project. For the detail, our guides on extension planning permission, permitted development versus planning permission and building warrants in Scotland explain exactly what applies and when.

If you are still at the stage of choosing who should carry out the work, our guide on how to choose a builder in Aberdeen sets out what to look for and the questions worth asking before you sign anything.