For example, if the basement is going to be heated and used for living space it needs two exits to the outside, and must provide enough light and ventilation. Open shafts, called light wells, built alongside a basement are the usual way of bringing light in through windows in the basement wall. Designers sometimes find creative ways to accomplish these practical goals. Los Gatos architect Peter Duxbury, whose firm is in Los Altos, says there's a basement in Los Altos that butts up to a swimming pool. The daylight pours down through the swimming pool and then through a glass wall that separates the pool from the basement.
Most cities require the basement to follow the footprint, or outline, of the house.
After that, Los Altos changed the code. Basements must meet California's strict building codes, and that's not cheap. Much of the expense of creating a basement is in the costs relating to heavy-duty construction. With California's seismic regulations, basements need a lot of reinforcement. A lot of reinforced steel goes into the walls, floor and ceiling of a California basement.