(1) Except as permitted by Sentence (2), a library book storage room that is not normally accessible to the public shall be separated from the remainder of the building by a fire separation with a fire-resistance rating not less than 2 h if it,
(a) is more than 250 m2 in area, or
(b) contains book stacks that,
(i) are more than 10 m high, or
(ii) penetrate more than one floor assembly.
(2) The fire separation required by Sentence (1) is not required if the book storage room is sprinklered.
(3) Open book shelves are permitted above and below a mezzanine floor in a library building provided the height of the shelves is not more than 2.1 m but not more than 75% of the floor-to-ceiling height of the space above or below the mezzanine floor assembly.