9.10.16.

(1) Concealed spaces in interior walls, ceilings and crawl spaces shall be separated by fire stops from concealed spaces in exterior walls and attic or roof spaces.

(2) Fire stops 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.

(3) Fire stops 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.

(4) In unsprinklered buildings of combustible construction, every concealed space created by a ceiling, roof space or unoccupied attic space shall be separated by fire stops into compartments of not more than not more than 300 m² in area where such space contains exposed construction materials having a surface flame-spread rating greater than 25.

(5) No dimension of the concealed space described in Sentence (4) shall exceed 20 m.

(6) 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 stops at intervals of not more than 20 m and at points where such concealed spaces extend across the ends of required vertical fire separations.

(1) Except as permitted in Sentences (2) and (3), fire stops shall be provided to block off concealed spaces within wall assemblies, including spaces created by furring,

(a) at each floor level,

(b) at each ceiling level where the ceiling contributes to part of the required fire-resistance rating, and

(c) at other locations within the wall, so that the distance between fire stops does not exceed 20 m horizontally and 3 m vertically.

(2) Fire stops required in Sentence (1) are not required provided,

(a) the width of the concealed wall space does not exceed 25 mm,

(b) the exposed construction materials within the space are noncombustible, or

(c) the exposed construction materials within the space, including insulation, but not including wiring, piping or similar services, have a flame-spread rating of not more than 25.

(3) Fire stops required in Sentence (1) are not required provided the wall space is filled with insulation.

(1) Except as permitted in Sentence (2), fire stops shall be constructed of,

(a) not less than 0.38 mm sheet steel,

(b) not less than 6 mm asbestos board,

(c) not less than 12.7 mm gypsum wallboard,

(d) not less than 12.5 mm plywood, OSB or waferboard, with joints having continuous support,

(e) no fewer than 2 layers of 19 mm lumber with joints staggered,

(f) not less than 38 mm lumber, or

(g) materials conforming to Sentence 3.1.11.7.(1).

(2) In a building permitted to be of combustible construction, semi-rigid fibre insulation board produced from glass, rock or slag, is permitted to be used to block the vertical space in a double-frame wall assembly formed at the intersection of the floor assembly and the walls, provided the width of the vertical space is not more than 25 mm and the insulation board,

(a) has a density not less than 45 kg/m³,

(b) is securely fastened to one set of studs,

(c) extends from below the bottom of the top plates in the lower storey to above the top of the bottom plate in the upper storey, and

(d) completely fills the nominal gap of 25 mm between the headers and between the wall plates.

(1) Where fire stops are pierced by pipes, ducts or other elements, the effectiveness of the fire stops shall be maintained around such elements.