Westminster City Council has introduced a levy on the construction of basement extensions.

Now, homeowners in the London borough who wish to extend their property underground must pay a further £8,000 on average and up to £30,000 for bigger developments to fund the council’s new ‘subterranean squad’ of basement monitors.

The levy comes as part of the council’s new code of construction practice and sets out a clear best practice for building sites such as basements. The code will also be rolled out over the next few months to cover bigger developments in the city.

In the last five years, Westminster City Council has received 150 applications a year on average and has seen a trend towards more ‘iceberg’ basements where homeowners dig down by one or two storeys.

The new rules include planning controls limiting basements to a single storey and no more than 50% of total garden land.

The new ‘subterranean squad’ will:

Make sites coordinate their deliveries to reduce the impact on residents

Check that developers are keeping neighbours informed

Enforce stricter working hours so as to avoid noisy works at inconvenient times such as Saturday mornings

Provide a point of contact for residents with complaints – with the power to enforce against overly noisy sites under statutory powers

Monitor the level and impacts of traffic to sites

Police development sites of over 10 residential units, or over 1000 m2 commercial floor space.

Robert Davis, Westminster City Council Deputy Leader and Cabinet Member for the Built Environment, commented: “We are sticking up for local residents, many of whom have found the explosion of basement development in recent years hellish. It is right that those who want to build basements should contribute to this new service, which will work to help mitigate the negative impacts.

“Westminster City Council supports the right kind of growth and is not against all basement development, but they must be carried out in a way that is considerate to local residents and the environment.”