With their underground swimming pools, cinemas and art galleries, London’s luxury basement developments have long provoked envy and disgust as depositories for the hidden wealth of the super rich.
But a new study, which has mapped all the 7,328 basements approved by 32 boroughs and the City of London between 2008 and 2019, has found that the majority of these developments were built for middle-class professionals rather than oligarchs, with the researchers saying they have become as normal as loft conversions.
The schemes contain 532 swimming pools, 814 cinemas, 1,695 gyms, 689 wine cellars, 607 games rooms, 342 steam rooms or saunas and 154 staff quarters, according to an analysis of planning applications by researchers at Newcastle University’s School of Architecture, Planning & Landscape.
Their report, Bunkering down? The geography of elite residential basement development in London, calculated that the combined depth of all of these schemes would be 15.8 miles (25.5km), equivalent to 31 times the height of the world’s tallest building, the Burj Khalifa in Dubai.
The researchers also estimated that more than 1.782m cubic metres of earth have been excavated from under Greater London to construct these basements – 12 times the volume of St Paul’s Cathedral.
In the aftermath of Monday’s torrential rain in London, local residents, MPs and environmental experts raised concerns that the proliferation of basement developments contributed to the flooding of hundreds of properties.
Queen guitarist Brian May posted a video on his Instagram account to show the extent of the damage to his Kensington home, which he claimed was “almost certainly the result of all the basement building that has been plaguing this area for the past 10 years”.
The scale of this building work has provoked planning battles in some of the capital’s wealthiest neighbourhoods. Robbie Williams’ plans to build an underground swimming pool and gym beneath his Grade II-listed home in Holland Park, west London, triggered a five-year dispute with his neighbour, Led Zeppelin guitarist Jimmy Page.
The study classified the basements, most of which the researchers said have been built or were under construction, into three size categories. Standard developments of a single storey made up almost 80% (5,813) of the schemes, with Hammersmith and Fulham having the highest number (1,285).
Another 1,344 schemes (18.3%) were classified as large basements, big enough to contain a swimming pool. The researchers also identified 171 (2.3%) mega-basements, some of which were three storeys in depth and extended under the garden. Kensington and Chelsea has the highest number of both these types, followed by Westminster.
The researchers also highlighted income inequality in London’s wealthiest boroughs, with 163 basements identified within 1km of Grenfell Tower, including 49 classified as large or mega.
Other amenities uncovered in the study include 71 libraries, 41 bars, 30 music rooms and 30 art spaces.
The study’s lead researcher, Roger Burrows, professor of cities at Newcastle University, said it found that booming house prices in the 2010s had made basement developments a logical choice for affluent Londoners in areas such as Hammersmith and Fulham, Islington and Hackney, who wanted to maximise the value of their property. “What we’ve seen is a normalisation of single-storey basements as the 21st-century version of the loft conversion,” he said.
Mary Dhonau, a former CEO of the National Flood Forum and now an independent flooding expert, described the study’s findings as “mind blowing”. She added: “I hope that Monday night was a stark reality check for planners. We should not be excavating huge basements and displacing soil that we need to percolate rain, especially in built-up areas.”
Karen Buck, Labour MP for Westminster North, said many constituents had raised concerns that the scale of basement excavation was a contributing factor to the flooding. “We have had reports that big basements have been flooded in St John’s Wood, which is on a hill,” she added.
The number of large and mega basements approved for development has declined in recent years, due to more stringent planning rules.
Building firms said construction of standard-sized basements had also slowed during the pandemic, probably due to job insecurity among middle class professionals. But Mike Wiseman, partner at the Basement Design Studio, said they had started to happen again since Christmas.
He added that the firm had recently completed a 250 sq metre basement underneath a listed building in St John’s Wood, with another, approximately 279 sq metres, currently going through planning approval.