Side Extension

Appearance

It is common practice for extensions to match the appearance of the original house, even more so if going through the Permitted Development route. This usually applies to the finish materials, types of windows and doors, and the roof shape. Most councils would have slightly stricter rules when it comes to side extensions done with a planning permission. Unlike rear extensions, side extensions can usually be seen from the public highway, therefore, planners would prefer those extensions not to detract too much from the original appearance of the house and the street scene. A more modern looking side extension to an otherwise traditional house is still possible, if its design is strong and provides clear advantages that the council can recognise.

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Overlooking

Side-facing windows, in most cases, are only allowed to be frosted and non-openable if there is potential for overlooking into your neighbours’ property. Hence, habitable rooms, like a bedroom or a living room, should ideally make use of front and rear facing windows only, which could result in limitations on things like the number of bedrooms, the living area size etc. It is common practice to either have no side-facing windows in a multi-storey side extension, or only have them in bathrooms, hallways or storage areas.

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Further Considerations

A side extension, in many cases would result in loss of access or reduced access to the rear garden from the highway or the front garden/driveway. It can also result in your property becoming terraced or semi-detached, which can affect its market value.

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Oftentimes the main staircase is adjacent to the side wall of the house – with some staircases being quite valuable, it is important to establish from early on if it is going to be an issue for the desired design, if the staircase is to be moved, replaced etc.

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Large openings in the side wall of the original house will require the introduction of significant structural frames, possibly driving up the cost of the alterations.

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With any extension there is always risk of building on top of existing sewer pipes, manholes or other types of below ground services. The appropriate measures should be taken to prevent compromising the services and the way they are maintained, or, if found to be more practical, for moving them to a more suitable location.

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Permitted development

Multi-storey side extensions are not permitted development and can only be constructed by acquiring a planning permission.

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Single-storey side extensions are often constructed under Permitted Development, as it is a straightforward option to deal with, provided the extension complies with the following:

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• It matches the external finishes and appearance of the original house.

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• It does not extend beyond the original front and rear walls.

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• The width of the side extension should not be greater than half the width of the original house

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• The height of the side extension must not exceed 4 meters

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• If the extension is within 2 meters of the boundary, the maximum eaves height should not exceed 3 meters

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• Its footprint, combined with all other extensions and outbuildings, must not add up to more than 50% of the original garden area.

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• Most councils would require that the extension be visually subordinate to the original house, often through having the front wall of the extension stepped in from the original front elevation, usually by 1 meter. In the most common case of pitched roof houses, stepping in the front wall would also result in a lower ridge line of the extension roof, further highlighting that an extension is subordinate to the main house.

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Constructing any item allowed under permitted development, does not limit your future permitted development rights, with a small exception when it comes to multi-storey rear extensions.

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It is important to remember that a wraparound extension will also require planning permission.