Cal. Health & Safety Code § 17958.11

(a) Any city or county may adopt alternative building regulations for the conversion of commercial or industrial buildings, or portions thereof, to joint living and work quarters. As used in this section, “joint living and work quarters” means residential occupancy by a family maintaining a common household, or by not more than four unrelated persons, of one or more rooms or floors in a building originally designed for industrial or commercial occupancy which include (1) cooking space and sanitary facilities in conformance with local building standards adopted pursuant to Section 17958 or 17958.5 and (2) adequate working space reserved for, and regularly used by, one or more persons residing therein.
The alternative building regulations adopted pursuant to this section shall be applicable in those geographic areas specifically designated for such occupancy, or as expressly permitted by a redevelopment plan with respect to a redevelopment project area. The alternative building regulations need not impose the same requirements as regulations adopted pursuant to Section 17922, except as otherwise provided in this section, but in permitting repairs, alterations, and additions necessary to accommodate joint living and work quarters, the alternative building regulations shall impose such requirements as will, in the determination of the local governing body, protect the public health, safety, and welfare.
(b) The Legislature hereby finds and declares that a substantial number of manufacturing and commercial buildings in urban areas have lost manufacturing and commercial tenants to more modern manufacturing and commercial premises, and that the untenanted portions of such buildings constitute a potential resource capable, when appropriately altered, of accommodating joint living and work quarters which would be physically and economically suitable particularly for use by artists, artisans, and similarly-situated individuals. The Legislature further finds that the public will benefit by making such buildings available for joint living and work quarters for artists, artisans, and similarly-situated individuals because (1) conversion of space to joint living and work quarters provides a new use for such buildings contributing to the revitalization of central city areas, (2) such conversion results in building improvements and rehabilitation, and (3) the cultural life of cities and of the state as a whole is enhanced by the residence in such cities of large numbers of persons regularly engaged in the arts.
(c) The Legislature further finds and declares that (1) persons regularly engaged in the arts require larger amounts of space for the pursuit of their artistic endeavors and for the storage of materials therefor, and of the products thereof, than are regularly found in dwellings, (2) the financial remunerations to be obtained from a career in the arts are generally small, (3) persons regularly engaged in the arts generally find it financially difficult to maintain quarters for their artistic endeavors separate and apart from their places of residence, (4) high property values and resulting rental costs make it particularly difficult for persons regularly engaged in the arts to obtain the use of the amount of space required for their work, and (5) the residential use of such space is accessory to the primary use of such space as a place of work.
It is the intent of the Legislature that local governments have discretion to define geographic areas which may be utilized for joint living and work quarters and to establish standards for such occupancy, consistent with the needs and conditions peculiar to the local environment. The Legislature recognizes that building code regulations applicable to residential housing may have to be relaxed to provide joint living and work quarters in buildings previously used for commercial or industrial purposes.