What lies beneath: Exploring London’s mega-basement trend


June 1, 2017



News emerged last month that neighbours of Kensington Palace, London residence of the Duke and Duchess of Cambridge, are up in arms about plans for a two-storey extension underneath the palace’s orangery. But is it really that surprising that Wills and Kate have joined the long line of London residents investing in so-called mega-basements? We don’t think so.

Space is at such a premium in the capital, digging down is an increasingly popular option, especially in London’s wealthiest neighbourhoods. More than 800 basement extensions have been carried out in Kensington alone. And these extensions don’t necessarily stop at one extra floor. Planning applications for two-floor basements in London more than doubled between 2010 and 2015. And some basement extensions go as deep as five floors underground – giving rise to the name ‘iceberg basements’, because so much of the property is hidden below ground.

While these basements may not be big enough to sink the Titanic, they’re certainly big enough to attract attention. Last year, billionaire Robert Beecham got the go-ahead to demolish his Primrose Hill mansion and build a new one in its place, complete with a massive 200-foot-long mega-basement. Plans for the basement include a swimming pool, Turkish bath and banquet hall for 80 people. In another project, architect Ian Hogarth created his own mega-basement beneath his West London end-of-mews house. Featured on the programme Grand Designs, the basement includes a lit-up dancefloor and is so huge that two-thirds of the property’s square footage is now underground.

It’s not all plain sailing for iceberg basements, though. Planning disputes have scuppered several projects, including Tory donor Edmund Lazarus’s 16,000-square-foot mega-basement that would have featured a cinema, cigar room and two-level gym. Kensington and Chelsea now restricts basement footprints to 50% of the total garden space, and Westminster council has introduced an £8,000 fee for basement planning applications. However, none of this is likely to put off the most committed and wealthy of London’s homeowners from investing in their own mega-basement. The trend for iceberg basements hasn’t sunk yet.

Here at Corebuild, we’re fascinated by anything that pushes design and build boundaries. To find out more about our expertise in London refurbishments and extensions, please drop us a line.