Councillors in Westminster are considering a ban on large basement extensions which the borough has likened to “the decks of a nuclear submarine”.
Expanding basements is becoming as increasingly popular way of increasing a property’s size without losing garden space and while working within the constraints of a densely built area.
Over the past three years the council says applications for basement extensions have risen from 79 in 2008/09 to 181 in 2011/12.
Many of the applications are centred around Belgravia, Mayfair, Knightsbridge, Marylebone and St John’s Wood, with some basements increasing to as many as three stories.
Westminster says the scale of such projects can cause huge problems and discomfort for neighbours.
Under proposed changes to the borough’s planning rules, all applications for extensions of more than one storey and over 50% of a property’s garden size will be recommended for refusal.
The council will also look to enforce a 1.2m minimum depth of soil between a garden and the roof of a basement extension.
The new rules are part of Westminster’s new local plan, which is being developed to cover a wide range of planning aspects, and will promote high quality developments while respecting Westminster’s unique heritage.
Depending on the outcome of a consultation, the rules will come into effect 2015.
Cllr Robert Davis, deputy leader of Westminster City Council, said: “This is about restricting developments akin to the decks of a nuclear submarine that are too large and cause real disruption for our residents.
“Currently the national planning guidance allows developers and homeowners to just down periscope and build whatever size they like – our residents have asked us to tackle this issue, and this is what we are doing.”