How to go from 500 to 1,200 square feet

As an example, take a basement excavation in Wimbledon Park reported by Metro in June. An enterprising flat dweller had a one-bedroom ground floor flat with a total area of 500 square feet with creaky steps leading down to a cramped garden.

First, the owner went for planning permission, which was granted. Her contractor dug down and out from street level and extracted 300 tons of material from the site. She created a two-level, three-bedroom duplex full of light, with a view of the garden from the master bedroom. The flat has gone from 500 sq. feet to 1,200 sq. feet.

What’s noticeable about this scheme is that the owner didn’t just think about plonking an extra bedroom on the back. They rethought the entire space, to extend over two floors and to work better as a living space. The former kitchen became the master bedroom, for example. The basement was used to create a stunning kitchen / living room facing onto the garden with clever built-in cupboards that contain the kitchen white goods and have hidden power supplies inside them.

It’s noticeable that many successful basement projects have feature stairs. This one has a custom made pine and steel staircase which looks stunning. The ceiling in the lower floor of this conversion and excavation was 2.7 metres, but the owner took advantage of the “side return”, a common feature of London houses, to have a part of the space with a soaring roof and light flooding in from three windows.

Use a company that understands the complexities

These are not, it has to be said, simple projects, and if you’re contemplating something similar, you need to talk to a basement company in London that has plenty of experience and is knowledgeable about how to handle any complications. There are lots of companies that will draw beautiful schemes – that’s great, but any company in this area also needs a lot of specialist knowledge, from how to deal with pipes in the ground, to the behaviour of the water table in your area.

Make sure that the company you use has a double certification. Firstly, they need to be a full member of the British Structural Waterproofing Association (BSWA). This is a body that plays a key part in protecting consumers from cowboy companies that promise cheap basement conversions, that turn out to be damp, leaking and dangerous. It’s basically about making sure that companies working in this field have enough expertise and skill to do the job properly.

Secondly, they need to be a member of the Considerate Constructors Scheme. This may even help you in achieving planning permission, and it will definitely help to gain acceptance from neighbours and others.