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House Extension Types

Different types of home extensions: Single storey rear, side and wrap around, double storey rear and side extensions, and over-structure extensions.

Single Storey House Extensions

A single storey extension is an add-on building which extends to the same height as the first level of your existing home. For that reason, it is usually less expensive than a double storey and an over-structure extension. Depending on the type of your property and your household's needs, you can choose between a rear house extension, side return and a wrap around extension. Below is a detailed explanation of each:

Rear House Extension

An extremely popular form of single storey extension, this form of home renovation is the type you’ll find in most interior design magazines and blogs. That’s because it beautifully takes in the fashion for the large open-plan dining room, kitchen and seating area, with glass sliding doors to extend the space out into the garden too. This type of extension gives a house a more communal feeling, with the family able to spend more time together in the one space. 

Side Return Extension

This type of extension is particularly popular with owners of older Victorian and Georgian tenements, which often tend to have the side alleyway ‘wasted space'. Often regarded as the least expensive form of house extension, it adds just a few metres to the kitchen width, but this should be sufficient to transform a small dark kitchen into an attractive kitchen-diner. Skylights or glazed ceiling are often used with this type of extension to allow natural light into the room. 

Wrap Around House Extension

To maximise ground floor potential of your home, it is possible to have a wrap-around extension built. This type of home renovation project involves using both the side and the back of the property, with the additional space ‘wrapping around’ the house. It means you get the benefit of extra space without having to use up too much of your garden. You could create a stylish deVOL inspired kitchen or a bright living room with sliding glass doors and roof lights.

Types of Extensions Wrap Around House Extension

Double Storey House Extensions

It may be more expensive at the outset, but a double storey extension is far more cost-effective than a single storey one in the long-run. Yes, you’ll need double the amount of materials for the walls and additional flooring, but you will be using the same foundations and roof for both, which happen to be the most expensive parts of the build overall. Two storey extensions are typically used to create an open plan kitchen and dining area with sliding or bifold glass doors and access the garden on the lower half. The second half can become anything you like, such as an additional bedroom, office or a large family bathroom. Double storey house extensions can be built onto the back or the side of the property. Rear double storey extensions can sometimes have flat roofs, while double storey side extensions will usually be required to have roofs of a pitched design similar in style to the existing roof, with the new roofline being preferably slightly lower than the main house.

Double storey side extension with a single storey extension at the back

Over-Structure House Extension

A clever way of using an existing building, such as one storey kitchen/dining area or an attached garage, is to create a new extension on top of it. In other words, you are 'building over' the existing structure. This type of home extension project is ideal if you want to add a large bedroom with en-suite to your home or a large playroom for the kids. It can prove to be one of the most expensive types of extension though, in the event the existing structure has single-skin brickwork (in which case more work would be required to strengthen it).

Types of house extensions - Over Structure Home Extension

Do I need planning permission to build a home extension?

Some extensions do not require planning permission thanks to the Permitted Development scheme. These are usually a rear single storey extension (which tends not to be visible from the front of the house) and even a double storey back extension. A single storey side extension may be ok if it's not higher than four metres and wider than half of the width of the original house. Wrap around, over-structure and double storey side extensions are more problematic from a planning point of view. However, it doesn’t mean that they can’t be built – just that you’ll have to get permission from your local authority first. They may also want it to comply with specific aesthetic guidelines, and even the positioning of sewer and water pipes can come into it. This is the reason it’s a good idea to first consult an architect or an experienced construction company before going ahead and making other plans. Below are some of the house extensions we have recently completed, explaining which ones needed planning permission and why.

Single storey rear house extension in Barnet, London

Single storey rear house extension - Permitted Development

Single-storey house extensions do not require planning permission if they are not higher than four metres and do not extend beyond the rear wall of the original house by more than six metres in case of a semi-detached or terraced house, or eight metres in case of a detached property. The extension must not cover more than half of the land surrounding the original property. If you live in a flat, maisonette or a listed building, or your home is in a conservation area, you will always be required to apply for planning permission.

This extension qualified under the Permitted Development rights as it extends less than six metres beyond the rear wall of a semi-detached home.

Double storey rear house extension in Hampstead, London

Large double storey rear house extension - Planning Permission

If you are building a double storey extension onto the rear of the house, you might qualify under the Permitted Development rights providing that your extension does not expand more than three metres beyond the rear wall, and is at least seven metres from the rear boundary. It must not be higher than the original house, and must not include a balcony, veranda, terrace or a raised platform. As with all types of extensions, the materials must be similar in appearance to the ones used on the original house. 

This large two storey extension with a partial basement and a terrace in Hampstead, North West London, required planning permission. 

Wrap around kitchen extension in West Hampstead, London

Wrap around extension - Planning Permission

While most single storey rear and side return house extensions can be built under the permitted development rights, wrap around extensions (which involve extending both the back and the side of the property, creating an L shape), such as this bright kitchen extension in West Hampstead, North West London, always require planning permission.

How to Apply?
You can apply for planning permission online at:

What are the most common uses for home extensions? 

By far, the most popular use for a home extension today is to extend the back of a property into a communal kitchen/dining space, while utilising garden space by ‘bringing the outdoors in.’ But other uses include an additional bedroom, games room, play room, home office and gym. What would you use yours for? 

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About Us

We are a Design and Build construction company specialised in building new homes, house extensions and loft conversions in North and North West London and Hertfordshire. We cover Notting Hill, Kensington, Maida Vale, Camden Town, Golders Green, Hampstead, Finchley, Hendon, Wembley, Colindale, Mill Hill, Harrow, Barnet, Hadley Wood, Borehamwood, Watford, Welwyn Garden City and St. Albans.