Cal. Civ. Code § 9
Buildings converted or altered
Operative Text
§ 9. Buildings converted or altered. 1. On or after July first, nineteen hundred fifty-two, no multiple dwelling shall be enlarged or its lot diminished so that the yard or other unoccupied areas shall be diminished in size or area below the minimum requirements of this chapter. 2. A building not a dwelling, if converted on or after July first, nineteen hundred fifty-two, to a multiple dwelling, shall thereupon become subject to all the provisions of this chapter applicable to new multiple dwellings of like class and kind. "Class" shall mean the use of a multiple dwelling for either permanent or transient occupancy or both. "Kind" shall mean the type of construction of a building, either fireproof or non-fireproof. 3. No dwelling shall be altered or converted so as to be in violation of any provision of this chapter relating to dwellings of like class and kind, and, except as provided in subdivision four, a dwelling, altered or converted to be occupied primarily for permanent-residence use, shall comply with article three; and a dwelling converted or altered to be occupied primarily for transient use shall comply with article four. 4. If any multiple dwelling three or more stories in height is altered after July first, nineteen hundred fifty-three so as to increase its height or bulk for living purposes or so as to increase the number of living rooms by more than twenty per centum, such dwelling shall be made to conform to the requirements of this chapter with respect to new dwellings of like class and kind erected after such date. 5. It shall be unlawful to convert a frame dwelling to a multiple residence, except that a frame dwelling not more than two stories and attic in height and erected before July first, nineteen hundred fifty-two, as a one-family or two-family residence may be converted to a multiple dwelling for permanent occupancy by complying with article three; and if such residence is converted to be occupied, as a rule, for transient use, it shall comply with article four.
N.Y. Mult. Resid. Law § 9 governs what happens when a building is enlarged, converted, or altered in ways that affect its status as a multiple dwelling. The provision establishes that conversions of non-residential buildings into multiple dwellings trigger the full set of standards applicable to newly constructed dwellings of the same class and kind, and that alterations cannot reduce required yard or open-space areas below minimum thresholds. Significant expansions of height or living space in taller buildings, and conversions of frame structures, are subject to specific additional requirements depending on the nature and timing of the work.
Plain English — not legal advice.
Property owners and managers operating under N.Y. Mult. Resid. Law § 9 generally ensure that any enlargement, conversion, or substantial alteration of a building is evaluated against the chapter's standards before work begins. Compliant operators confirm that proposed changes will not reduce yards or unoccupied areas below minimums, and that a converted non-residential building is brought into full compliance with the standards for new multiple dwellings of the applicable class and kind. When alterations to a three-or-more-story building increase height, bulk, or living rooms by more than twenty percent, operators typically verify conformance with the requirements for new dwellings, and frame-dwelling conversions are reviewed against the specific limitations set out in the provision.
General guidance for property managers — not legal advice for your specific situation. Consult an attorney for advice on your case.
Tenants living in buildings that have been converted or significantly altered may have rights under N.Y. Mult. Resid. Law § 9 if the building does not meet the standards that applied at the time of conversion or alteration. If a tenant believes a conversion was carried out without meeting the required class-and-kind standards — for example, inadequate open space or noncompliant construction — that concern can generally be raised with the local housing or building code enforcement agency, or noted as a potential violation in a housing court proceeding. Tenant-rights organizations can help residents understand whether § 9 requirements are relevant to conditions in their building and what general enforcement paths may be available.
General guidance for tenants — not legal advice for your specific situation. Consult a tenant-rights organization or attorney for advice on your case.
Generated September 13, 2026 — auto-generated, not yet human-reviewed. See /transparency for methodology.
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