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Creating Basement Extensions

It’s a truth universally acknowledged that space in cities comes at a premium – and it’s particularly true of London. Across the capital, homes are being added to, adjusted and expanded to create extra space. In some cases, the only way to add and maximise space is to go down. This has lead to basement extensions becoming an increasingly popular option. After all, they can accommodate a whole host of potential living spaces including cinema rooms, gyms, spas and underground car parks. This type of project has been become increasingly frequent in areas across west London, including Knightsbridge, Belgravia, Fulham and Notting Hill.

At Capital Interiors, we are particularly familiar with these basement conversions. In fact, we are currently constructing a two-storey basement in the heart of Kensington. Here are some photographs of the 17 metre deep excavation work:


Basement extensions are complex projects, and they require specialist knowledge from architects, civil engineers and project managers. Interestingly, converting a cellar from a storage area to a habitable space involves only a ‘change of use’ and, in itself, does not require planning permission. However, if you were to reduce the level of the floor in order to increase the height of the ceiling, it would be categorised as an extension due to the increase in volume of the room; in this case, planning permission would be required. Modest extensions and alterations don’t always require a planning application if they fall under the permitted development rights legislation, so it’s best to consult with an expert first.


Capital Interiors managed and contracted this basement extension, creating within it the perfect room for the ultimate cinematic experience. A cinema room tends to be a popular choice for this type of project, as a basement lends itself very well to this type of living space.


The success of a basement extension can be measured by how well it evokes a feeling of light and space. Careful consideration to the use of light is paramount, and using as much natural light as possible, or at least creating an illusion of it, is essential. Due to the lack of natural light available for this project, a multilevel ceiling was designed. The ceiling incorporated strategically placed lighting as well as a skylight which created a feeling of light, depth and space. The picture of the patio above shows the positioning of the skylight and provides a great example of how a seemingly unusable space can be transformed into an asset.