General commercial building. A commercial building, as defined under
the Building Code of New York State and any amendments or supplements
thereto, as Groups A1, A2, A3, A4, A5, B, E, F1, F2, H1, H2, H3, H4,
H5, I1, I2, I3, I4, M, S1, S2, and U, and any mixed-use building,
existing on the effective date of this chapter, shall be fully sprinklered,
except that such requirement shall not apply to any commercial or
mixed-use building existing prior to January 1, 1984, unless at any
time after January 1, 1984, the entire building, leased premises or
individual use, whichever shall be smaller, undergoes major expansion,
at which time the entire building shall be sprinklered.