The Multiple Dwelling Law (MDL)
The Multiple Dwelling Law (MDL) is a New York State statute that defines “private dwellings” (1–2 families) and “multiple dwellings” (3+ families) and then imposes detailed rules on the design, safety, light and air, fire protection, and occupancy of multiple dwellings, especially in cities like New York City. It divides multiple dwellings into Class A (permanent residence, 30 days or more) and Class B (transient, like hotels and certain rooming houses), and each class has different requirements and enforcement consequences.
Why MDL matters with DOB
For residential buildings, MDL provisions sit “on top of” the NYC Building Code and Zoning Resolution: DOB must enforce MDL requirements when it reviews plans, issues Certificates of Occupancy, or handles conversions and violations in multiple dwellings. For example, when a non‑residential building is converted to residential use, the number of units, light and air standards, and some high‑density rules are governed by MDL sections such as MDL § 277, which DOB and zoning guidance explicitly reference.
Related terms
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NEW YORK STATE MULTIPLE DWELLING LAW
