Live/work unit sizes are often set by local planning regulations and building codes. Minimum sizes are often a combination of the smallest space in which one might live plus a reasonable work space size. To distinguish live/work from straight residential, some cites have set sizes larger than typical apartment minimums, and San Francisco, for example, requires ceiling heights to be a minimum of fourteen feet. Oakland, California uses 660 square feet for the minimum live/work unit size, with the live portion not to exceed 1/3 of the area, or 220 square feet. Maximum sizes are rarely set, although many live/work building codes require a second means of egress from a unit over a certain size, say 2000 square feet.