Although these so-called iceberg homes are few and far between, there are now several properties across London with swimming pools, bowling alleys, cinemas and even tennis courts in their capacious basements. In Kensington and Chelsea only 10% of planning applications for basement construction are refused. No longer do the inhabitants pop out to the gym, they simply pop down to the basement.

Double the space

Although this type of mega basement construction in London tends to grab the headlines, homeowners all over the capital are digging down to create more space in their properties. Although a loft conversion is quicker and generally less disruptive, basement construction can be considerably more versatile and avoids the problems of restricted head height.

If you’ve already gone up, and you don’t have the space to go out, then going down – particularly if you already have a basement – can be a sensible choice. You’re also unlikely to need planning permission so long as you stay within the rights of permitted development.

An indestructible space

A basement can add real value to a family home, providing an indestructible inner space where teens can play their music loudly and boisterous kids can kick a football repeatedly against the wall without annoying anyone. Keep your below ground space in proportion with your existing home, and the chances are you can add at least 15% to the value of your home if the conversion is done well.

It’s worth checking that you have or can make adequate head height before you start, and that you’ll be able to let sufficient light enter from elsewhere. One popular solution is digging out under the garden and inserting a series of lightwells to let natural light flood in. Otherwise, plan your lighting very carefully so your basement is light and airy not dark and airless.

Where does the water go?

Of course one of the major issues when digging down in London is the upper aquifer, the layer of groundwater that many basement constructions fall foul of. Where once a basement would be tanked out to repel the water, now the preferred management system is to drain and pump, allowing the water to find it’s own way around a new obstruction. With many of London’s ancient rivers already captured in the sewerage system, water will always find somewhere to flow to.

Why you should consider an ‘iceberg home’

Of course, not many of us can afford the kind of luxury basement that holds a fleet of Ferraris or a garage full of Rolls Royces, but if you love where you live and don’t want to leave, then the ‘iceberg house’ can give you the flexibility of adding significantly more living space for far less than it would cost you to move. If you love your location but you need more space, then consider adding a playroom or dream kitchen diner right under your feet.