Cal. Civ. Code § 185

  § 185. Cellar ceilings. 1. Except as provided in paragraph g of
subdivision three of section one hundred seventy-one, the ceiling of the
cellar, or of the lowest story if there be no cellar, shall be
fire-retarded unless such dwelling is three stories or less in height
and the ceiling has already been plastered in a manner satisfactory to
the department.
  2. In lieu of the requirements set forth in subdivision 1. hereof,
buildings existing November first, nineteen hundred forty-nine, in
cities having a population between five hundred thousand and one million
having three stories or less in height and containing no more than six
families or eight roomers or lodgers, with no human occupancy in the
cellar or basement may comply by:
  I. providing two means of egress to any area of the third floor used
for human occupancy; and
  II. providing approved safety controls on all fuel burning devices in
basement or cellar; and
  III. fire-stopping of all openings in cellar or basement ceiling or
openings leading to the floors above from cellar or basement such as,
but not limited to, stud channels, openings around conduits, soil and
water pipes, ducts, pipe chases, and by complying with either IV or V
hereof;
  IV. providing an approved sprinkler system throughout entire cellar or
basement area; or
  V. a. providing fire-retarded ceilings at the first floor level; and
  b. providing sprinkler head or heads above each hot water heater,
furnace and all other fuel burning devices in basement or cellar; and
  c. fire-stopping all the interior entrances to any area of the third
floor used for human occupancy at the second floor level with
fire-retarded partitions, or equal construction, and a fire-retarded
self-closing door and assembly.