Basement extensions - our tips and advice

In this blog we discuss the advantages and disadvantages of basement extensions.

Basement extensions - our tips and advice

It's a huge risk putting a basement in a property, and it comes at a high price. Going down is the most expensive and problematic way to extend a home, costing about three times as much per square foot as a loft extension. Whether you make your money back depends on the type of house, the quality of work, the layout, interior design and natural light within the underground space. In pricey areas, where family houses sell for £750,000 or more, a basement is probably a better investment than elsewhere. If your street is full of starter houses or two-up-two-downs, you are unlikely to get your money back on a basement conversion.

Basement extensions are becoming increasingly popular because they can double a house's living space. Many family houses have adequate bedrooms - all those loft conversions - but the ground floor living area is cramped. Building downwards creates a whole extra floor for kitchen or playroom, games room, utility room or guest room, and also liberates space upstairs. But potential problems abound. Foundations may be unsound, and your neighbour's services may be running under your house. Drainage can cause problems, as ground water and waste have to be pumped out upwards from a basement. A lot of properties are built under the water table so with heavy rain and a breach in your tanking - the vital waterproof lining around floor and walls - you could end up with a surprise swimming pool down there.

If you go ahead, keep the ceiling height high - don't settle for less than 8ft - and put in as many sources of natural light as you can via windows, grilles, lightwells, sun tunnels, stairwells and skylights. If you have some extra money, spend it on making a beautiful, open staircase down to the basement - it will transform the space.

Finally, expect a long and dirty job, although many basement conversions are carried out through the front garden.