April 28, 2022
Re: Continuity of Required Fire Separation for a Secondary Suite
The project is a two level house with a secondary suite located in a portion of the upper level. There is a common roof space/attic area above both suites created by a 6 in 12 slope truss roof system. A girder truss is located directly above the vertical fire separation between the primary and secondary suite. The girder truss has roof framing components perpendicularly connected to it.
Applicable Code requirements: (BCBC 2018)
188.8.131.52. Permitted Openings in Wall and Ceiling Membranes
1) Except as permitted in Sentences (2) and (4), a membrane forming part of an assembly required to have a fire-resistance rating shall not be pierced by openings into the assembly unless the assembly has been tested and rated for such openings.
2) A wall or ceiling membrane forming part of an assembly required to have a fire-resistance rating is permitted to be pierced by openings for electrical and similar service outlet boxes provided such outlet boxes are tightly fitted.
3) Where boxes referred to in Sentence (2) are located on both sides of walls required to provide a fire-resistance rating, they shall be offset where necessary to maintain the integrity of the fire separation.
4) A membrane ceiling forming part of an assembly assigned a fire-resistance rating on the basis of Table 184.108.40.206.-B or Appendix D is permitted to be pierced by openings leading to ducts within the ceiling space
provided the ducts, the amount of openings and their protection conform to the requirements of Appendix D.
220.127.116.11. Concealed Spaces above Fire Separations
1) Except as provided in Sentence (2), a horizontal service space or other concealed space located above a required vertical fire separation shall be divided at the fire separation by an equivalent fire separation within the space.
2) Where a horizontal service space or other concealed space is located above a required vertical fire separation other than a vertical shaft, such space need not be divided as required in Sentence (1) provided the construction between such space and the space below is constructed as a fire separation having a fire-resistance rating not less than that required for the vertical fire separation, except that where the vertical fire separation is not required to have a fire-resistance rating greater than 45 min, the fire-resistance rating of the ceiling may be reduced to 30 min.
Decision being appealed (local authority’s position)
The local authority has determined Sentence 18.104.22.168.(1) requires a vertical fire separation to continue through the concealed attic space. The vertical fire separation must be continuous and cannot have wood truss members penetrating it.
The local authority acknowledges Sentence 22.214.171.124.(2) provides an exception if the ceiling below the concealed attic space is constructed as a horizontal fire separation. This would require the entire attic space (on both sides of the vertical fire separation) to be separated from the space below. Further, all penetrations through the ceiling membrane must be permitted/protected to maintain the integrity of the horizontal fire separation. The appellant’s proposal to construct only the secondary suite ceiling as a fire separation would not meet the requirements of this Sentence 126.96.36.199.(2).
The appellant considers the fire rated ceiling above the secondary suite only, with a combination of ionization and photoelectric hardwired and interconnected smoke alarms, does not warrant the requirement to continue the vertical fire separation into the attic to the underside of the roof. The appellant considers the fire tested assemblies listed in the BCBC take into account penetrations such as unrated attic access hatches.
Appeal Board decision #1887
It is the determination of the Board that the Code describes two options for the fire separation between the suites, both of these options are acceptable:
- The vertical fire separation is continued through the attic space to the underside of the roof sheathing, or
- The vertical fire separation abuts a ceiling that is a horizontal fire separation at both sides of the vertical fire separation with the appropriate fire resistance rating. Openings or penetrations in this horizontal fire separation must be protected by the requirements of the Code including Article 188.8.131.52. This applies to the entire ceiling of the upper level.
Reason for decision
The Board used for guidance the Illustrated User’s Guide - NBC 2015: Part 9 of Division B, Housing and Small Buildings referencing Article 184.108.40.206.
Chair, Building Code Appeal Board