9.10.16.1. Required Fire Blocks in Concealed Spaces

 9.10.16.1. Required Fire Blocks in Concealed Spaces

This Article determines where fire blocks are required. The function of fire blocks is to reduce the extent of fire spread in buildings until #evacuation can be safely carried out, and to allow #firefighting to commence before damage to a building becomes extensive.

Fires originating in concealed spaces, or that gain entry through openings in enclosing #membranes, can travel undetected from one part of the building to another. This may jeopardize the occupants‘ escape, and make firefighting very difficult.

It may also neutralize the effectiveness of fire compartments in controlling the extent of fire damage. Unless such spaces are completely filled with #insulation or are made from material that will limit flame travel (i.e., a flame-spread rating of 25 or less), or the width of the concealed space is less than 25 mm (1 in.) to limit air supply, fire blocking must be provided at strategic locations to restrict the spread of fire.

In small spaces, such as #stud, #joist and #furring spaces, fire blocking usually consists of the same material as the #framing and furring. In larger spaces, such as attics and soffits, sheet material is generally used such as 12.7 mm (1/2 in.) gypsum board, 12.5 mm (1/2 in.) #plywood, oriented #strandboard (OSB) or #waferboard, or 0.38 mm (28 gauge) sheet steel. A double layer of board #lumber is also permitted if the joints are staggered between layers. Fire blocks can be pierced by piping, wiring or ducts, provided the #openings around the penetrations are tight-fitting or sealed with a fire-resisting material.

Concealed spaces that are very shallow (25 mm (1 in.) or less), or that are filled with mineral wool, do not facilitate the propagation of fire within the space, making it unnecessary to install fire blocks. 

Figure 9.10.-31 shows where fire blocking is required in a typical house.

Quoted from Illustrated Users' Guide -- NBC2015

#fireblock #concealedspace #firecompartments #flamespreadrating #gypsumboard #sheetsteel