It’s currently the height of fashion to plumb the depths and build a fancy basement beneath your London townhouse. Ross Clark on why — and indeed whether — the only way is down
William Lyttle, who died in 2010 aged 79, was an eccentric who spent 40 years digging tunnels beneath his large house in north-east London, before being caught and prosecuted by Hackney council when a section of pavement collapsed. But he was also something of a pioneer. Nowadays, everyone with money seems to be burrowing or planning to burrow beneath their London homes. David Cameron did it in Ladbroke Grove, sculptor Anish Kapoor in Chelsea, comedian Ricky Gervais in Hampstead.
The fashion for digging basements beneath London houses seemed at one time to be a story of the boom, a final phase of madness and excess before the floor metaphorically fell in on the property market in 2008. Yet more audacious schemes are being undertaken by the year. The practice has given rise to a term — the iceberg house — to describe a modest-looking property which conceals a vast basement beneath. One house in Holland Park has a basement boasting a swimming pool, gym and cinema. Dig-outs are no longer restricted to a single storey: below a house in Graham Terrace, Westminster, lies a four-car garage — and beneath that lies a swimming pool.
Designs are being forced through circumstance to become increasingly innovative. Denied permission for a large light well, one homeowner built a large, glass-bottomed pond above his basement, allowing natural light to flood through the ceiling and with the novelty of being able to look up and see fish swimming above your head.
Basements are a product of London’s extraordinary property prices and restrictive planning laws. In few locations would they make economic sense. But when you have a large number of extremely wealthy people wanting to live in a few streets of 200-year-old properties built for people of more modest wealth, properties which may not be knocked down and redeveloped, there’s little choice but to go downwards.
The basic cost of digging out a basement — excluding the finishing of the rooms thus created — is around £3,000 per square metre of floor space. Only in the past ten years has the value of floor space in prime central London reached this sort of level. But the economics are blurred by the fact that basement dig-outs provide the only opportunity to create large, unobstructed floor areas suitable, for example, for a swimming pool. They’re also a natural location for panic rooms.
The practice of digging out basements has not merely survived boom and bust; it has also survived campaigns by neighbours and conservationists. In 2009 a spate of flooded cellars in Old Church Street in Chelsea was blamed by some residents on basements which had recently been constructed nearby. In contrast to the traditional London basement, which has walls of porous bricks and lime mortar, a modern basement is a concrete box which presents an impediment to underground flows of water.
The borough of Kensington and Chelsea commissioned a study by consulting engineers Ove Arup, which concluded that basements — at least on the scale constructed so far — were not creating a flood risk. It did, however, lead to a policy limiting basements to covering 85 per cent of a plot — leaving, in effect, channels of earth to allow underground flows of water.
The law, generally, is very kind to the practice of burrowing. Britain’s planning system is geared up to rule on developments you can actually see. Basements, as a result, tend to sail past the planners. They’re an issue for the parallel system of building control, but again the law is generally helpful.
Even if you share a wall with your neighbour there is little he can do to prevent you digging out a basement. You have to consult him, but so long as your builders are competent enough to dig out your basement without damaging his house, all he can really do is stand around gritting his teeth.
BASEMENT-DIGGING DOES sometimes go wrong, but it doesn’t tend to be the wealthier residents of Kensington and Chelsea who get into trouble. The ones who burrow themselves into a mess tend to live in cheaper areas, see a glorious London basement in a glossy magazine and have a rather optimistic approach to the economics.
There is a sad story of a couple in Cheltenham who fancied building an underground house in their back garden — and did so on the TV show Grand Designs. Halfway through construction, the walls started leaking and had to be plugged. They finally achieved their dream home but had to sell it to pay off their loans. Trouble was, no one showed a lot of interest in paying £650,000 for an underground house — not when larger local houses above ground sell for less. For years they tried to give it away as a competition prize, without success.
It’s easy to get fooled by the London property market into thinking that you can’t go wrong with adventurous alterations. But unless you live in a small area of prime central London it’s probably best to forget the Hobbit option and stick to a conventional house with four walls, a roof, a few windows.
Ross Clark is a property expert who writes for The Daily Telegraph and The Spectator