Unless you are specifically after a home cinema, sauna or photographic darkroom, the key factor in good design is how to manage the question of daylight.

The art is to make the space feel as un-basement-like as possible. The first thing to think about is whether it will be possible to put windows in any of the walls. This usually means external excavation with a light-well or basement-level terrace.

One common mistake is to think that high-level windows will suffice. If anything these are worse than having no windows at all, as they really enhance the sense of being in a cell. Standard-height windows or even better, full-length glazed doors out to a light-well, will transform a room below ground.

If it’s not possible to build a light-well, I would always look at the possibility of forming some double-height space internally. This would mean removing an area of the ground floor so that daylight can pour down to the basement below. Despite losing some of your ground floor, this can work really well. The lack of direct windows is compensated for by the sense of double-height space and the daylight washing down from above. Internal balconies can work well in these situations, too.

Bear in mind is that basements are probably the most expensive type of extension – if there’s an alternative available, such as a loft or rear extension, it may be worth considering.

Hugo Tugman, Architect Your Home