(1) Except as permitted by Sentences (2) and (3), the flame-spread rating shall be not more than 75 for the interior wall finish of,
(a) a public corridor,
(b) a corridor used by the public in,
(i) an assembly occupancy, or
(ii) a care, care and treatment or detention occupancy,
(c) a corridor serving classrooms, or
(d) a corridor serving sleeping rooms in a care, care and treatment or detention occupancy.
(2) The flame-spread rating limit specified in Sentence (1) does not apply to corridors referred to in Sentence (1) provided the flame-spread rating is not more than,
(a) 25 on the upper half of the wall, and
(b) 150 on the lower half of the wall.
(3) The flame-spread rating limits specified in Sentences (1) and (2) for corridors referred to in Sentence (1) do not apply to a corridor in which the flame-spread rating is not more than 150 provided the floor area is sprinklered.
(4) The flame-spread rating limits specified in Sentences (1) to (3) apply to occupancies in the corridor as well as to the corridor itself.
(5) Except in a floor area that is sprinklered and as permitted in Sentence (6), the interior ceiling finish of corridors and occupancies referred to in Sentences (1) and (4) shall have a flame-spread rating not more than 25.
(6) The flame-spread rating limits specified in Sentence (5) do not apply to a corridor in which the flame-spread rating is not more than 150 provided the floor area is sprinklered.