Code: MDL (official acronym)
Description: New York State law (Multiple Dwelling Law) that sets minimum safety, health, and occupancy rules for apartment buildings and other multi-family residential buildings (3 or more units) in New York City. It defines Class A (permanent residences) and Class B (transient, such as hotels and rooming houses) dwellings, each subject to different design, fire safety, and enforcement requirements.
Practical Meaning: When MDL appears in a DOB violation, it means the violation is based on the Multiple Dwelling Law. If you own or manage a building with 3 or more units, MDL rules apply to you — covering occupancy limits, use of units (Class A for permanent residents, Class B for transient guests), fire safety, and structural standards. Ignoring MDL-based violations can result in fines and enforcement action by the NYC Department of Buildings.
Where You May See It: You may see this name or the short form “MDL” in DOB and HPD violation notices, in BIS and DOB NOW building classification codes, in architect or engineer reports, or in city rules that talk about Class A and Class B multiple dwellings.
Why It Matters: This law affects whether a building is legally a “multiple dwelling,” what type it is (Class A or Class B), and what standards apply for occupancy, fire safety, light, air, and sanitation, which can change what work is required and which violations you may receive.