Why a basement is a sound investment in West London

For a homeowner in West London, adding space is rarely a matter of choice between up, out and down. The plot is fixed, the roof is often already converted and the garden is usually protected or too small to give away. So people go down.

What a basement gives you

A basement takes the rooms that do not need daylight and puts them underground: a cinema, a gym, a wine cellar, plant, utility and storage. That frees the floors above for bedrooms and living space, which is the part that actually changes how the house works.

It also adds floor area without changing the elevations, which is why it survives planning in a conservation area where a rear extension would not.

Does it pay?

That depends on three things: what the finished space is worth per square foot in your postcode, what the build actually costs on your ground conditions and access, and how much of the value you recover when you come to sell.

Nobody can promise a return on it. Anybody who quotes you a fixed percentage has not seen your house. What we can do is give you an accurate construction figure early, so the arithmetic is yours to do. Our own basement rates by specification are published in the NU Build Cost Calculator.

Modern basements are not cellars

A well-designed basement is bright and dry. Lightwells front and back, a subterranean courtyard, or a generous stair opening all bring daylight down, and 2.8 to 3 metres of finished ceiling height is what stops it feeling underground.

All of that has to be designed in before excavation, because none of it can be added afterwards.

Energy and running cost

Below ground, the surrounding earth moderates the temperature, so a properly insulated basement is cheaper to heat than the equivalent floor above it. It does need designed ventilation and a maintainable drainage and pump arrangement, which is where badly built basements fail.

Getting it right

A basement is a structural, planning and neighbour problem before it is an interior. Before you appoint anybody, read the ten checks worth making, and planning a basement conversion for the surveys and the sequence.

NU Projects builds basements in West London, and takes the planning, the party wall process, the structural design, the waterproofing and the fit-out through one contract. Tell us about the house.