Cal. Civ. Code § 30

  § 30. Lighting and ventilation of rooms. 1. The provisions of this
section shall apply only to multiple dwellings erected after April
eighteenth, nineteen hundred twenty-nine, and shall apply to all such
dwellings unless otherwise expressly limited.
  2. Except as in this section and in sections thirty-three,
seventy-six, one hundred fifteen, one hundred sixty, one hundred
seventy-six, two hundred, two hundred thirteen, two hundred fifty and
two hundred fifty-one otherwise expressly provided, every room,
including kitchens, water-closet compartments and bathrooms, shall have
at least one window opening directly upon a street or upon a lawful
yard, court or space above a setback upon the same lot as that occupied
by the multiple dwelling in which such room is situated. Every such
window shall be so located as to light properly all portions of the
room.
  3. No room in any apartment of three rooms or less, and no room in any
non-fireproof apartment, shall extend in depth, from a street or yard on
which it faces, more than thirty feet without a window opening on a
lawful court.
  4. a. Nothing in this section or section twenty-six shall be construed
as prohibiting the windows or doors of any room from opening on a
partially-enclosed balcony or space above a setback, provided such
balcony or space opens directly to a street or to a lawful yard or court
and the area of the front of the balcony or space which is open to the
outer air is at least equal to seventy-five per centum of the floor
surface area of such balcony or space. Any living room thus lighted and
ventilated by windows or doors opening on such balcony or space shall be
at most thirty feet in depth measured from the extreme outer face of the
wall forming the partial enclosure of the balcony or space. The windows
or doors providing light and ventilation for a room or rooms opening
exclusively on such a balcony or space shall have altogether at least
the area of one-tenth of the combined floor surface of such room or
rooms and the portion of the balcony or space directly adjoining and in
front of such room or rooms.
  b. On a fireproof dwelling a balcony or space above a setback
permitted under paragraph a of this subdivision may be completely
enclosed, provided the outer enclosing wall or walls and roof are
constructed of incombustible materials and the walls are glazed with
clear plate glass or plastic equivalent and such glazed wall area is
equal to at least fifty per centum of the area of the interior walls
enclosing such balcony or space. At least fifty per centum of the glazed
area shall be openable directly upon a street or upon a lawful yard or
court. No window shall open from any bathroom, water-closet compartment
or cooking space upon such enclosed balcony.
  c. The enclosure on any balcony or a space above a setback shall not
(1) be more than one story in height or (2) be erected in violation of
the provisions of paragraph a of subdivision six of section one hundred
two of this chapter.
  5. No multiple dwelling shall be so altered as to diminish the light
or ventilation of any room or public hall or stairs in any way not
approved by the department.
  6. No window shall be required in any public room of a fireproof
multiple dwelling if such room is used solely for storage purposes or
has adequate mechanical ventilation maintained to provide at least the
number of changes of the air volume of such room approved by the
department as necessary for the health and safety of the occupants of
such dwelling. Any fresh air supply system required by the department
for such purposes shall be provided with adequate means for removing
dust from the incoming air and with adequate means to heat such air at
least to sixty degrees Fahrenheit.
  7. No required window shall open upon any offset or recess less than
six feet in width except a window of a water-closet compartment,
bathroom, or stair or of a cooking compartment less than eighty square
feet in floor surface area.
  8. (a) The windows in every room, except a water-closet compartment,
bathroom, or cooking space less than eighty square feet in floor surface
area, shall have a total area at least one-tenth of the floor surface
area of such room and every window in such a room, including a mullioned
casement window, shall be at least twelve square feet in area.
  (b) All required windows shall be so constructed that at least
one-half of their required area may be opened, except that a mullioned
casement window, if otherwise large enough to supply the window
requirements of the room, need be readily openable to the outer air only
to the extent of five and one-half square feet of its area.
  (c) Where fresh air is furnished in any room through a mechanical
ventilating unit or system which is an integral part of the dwelling
structure and capable of introducing not less than forty cubic feet of
air per minute, the required window area in such room need be openable
only to the extent of twenty-five per cent of such window area but in no
event less than five and one-half square feet.
  9. Transoms or partition sash, or louvres having a minimum area of 144
square inches and arranged to be opened or closed, shall be provided to
private halls or to adjoining rooms to secure through-ventilation
whenever required by the department, but no such transom or partition
sash or louvre shall be required in a room having two windows opening to
the outer air if each window is at least nine square feet in area, or in
a room having a mullioned or single window with an aggregate area of at
least eighteen square feet.
  10. All windows and their assemblies in walls situated on a lot line,
except those facing on a street, shall be fireproof, with assemblies
having a fire-resistive rating of at least three-quarters of an hour and
glazed with wire glass at least one-quarter of an inch thick. Every
opening in a wall situated on a lot line which is less than fifty feet
in a vertical direction above a non-fireproof roof of another structure
within a distance of thirty feet of the wall in which the opening is
located shall be an automatic fireproof window.