(1)
Concealed spaces in interior walls, ceilings, floors and crawl spaces shall be separated by fire blocks from concealed spaces in exterior walls and attic or roof spaces.
(2)
Reserved.
(3)
Fire blocks shall be provided at all interconnections between concealed vertical and horizontal spaces in interior coved ceilings, drop ceilings and soffits where the exposed construction materials within the concealed spaces have a surface flame-spread rating greater than 25.
(4)
Fire blocks shall be provided at the top and bottom of each run of stairs where they pass through a floor containing concealed space in which the exposed construction materials within the space have a surface flame-spread rating greater than 25.
(5)
Where not sprinklered, concealed spaces of combustible construction created by a ceiling, roof space or unoccupied attic space shall be separated by fire blocks into compartments
(a)
not more than 60 m in greatest dimension, and
(b)
where such space contains exposed construction materials having a surface flame-spread rating greater than 25, not more than 300 m
(6)
No dimension of the compartment described in Clause (5)(b) shall exceed 20 m.
(7)
Concealed spaces in mansard or gambrel style roofs, exterior cornices, balconies and canopies of combustible construction in which the exposed construction materials within the space have a surface flame-spread rating exceeding 25 shall have vertical fire blocks at intervals of not more than 20 m and at points where such concealed spaces extend across the ends of required vertical fire separations.