Do Apartments Need Title 24?
Yes. A building of three or more dwelling units falls under the multifamily standards, and which form set applies depends on whether it has three habitable storeys or four or more.
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Which standards apply
Since the code was restructured, multifamily buildings have their own subchapters rather than being handled as a variant of residential. A building with three or more dwelling units is multifamily — townhouses excepted — and that is the set of requirements it is assessed against.
Within multifamily there is one further split. Low-rise multifamily means up to three habitable storeys and uses the low-rise multifamily form family. High-rise multifamily means four or more habitable storeys above grade and uses the nonresidential, hotel/motel and high-rise multifamily set instead.
What counts as a habitable storey
This is worth getting right, because it decides which form family a project is on. A habitable storey is one containing space in which people may live or work in reasonable comfort, and which has at least half of its associated volume above grade. A partly buried podium or garage level can therefore fall on either side of the definition depending on how far above grade it sits, and that single question can move a building from three storeys to four.
The discontinuity that used to exist
Until the restructuring, moving a design from three storeys to four changed the requirements sharply, because it crossed from one rule set into a quite different one. The current code deliberately aligned high-rise residential requirements with low-rise multifamily ones, so the step is far less abrupt than it was. The form family still changes at four storeys; the substance of what has to be achieved is now much closer.
Newly constructed low-rise multifamily also carries a solar photovoltaic requirement, with a short list of exceptions that have to be established for the specific building rather than assumed.