24 201326 ALT

Project Description

Alternative Solution - State Railing Corporation (State) retained HOD engineering Inc. (HOD) to comment on the use of tempered glass thicker than 6mm in the Type RL-T2.2 railing on 88 Queen 2A project, located at 25 Dalhousie St. and 30 Mutual St., Toronto, Ontario. The intention of table 2.1.1.1 of the SB-13 is to ensure that the appropriate type of glass is used based on the proximity of the glass to a floor edge, according to the breakage patterns of the different types of glass. Given that the glass in this case is located more than 150mm from the floor edge, the table allows tempered glass to be used. However, SB-13 and the Ontario Building Code 2012 (OBC 2012) also requires that guards, including glass, be designed for combinations of wind and guard loads. For this requirement, 6mm tempered glass was not adequate for Type RL T2.2 railing based on the glass size and railing geometry. Satisfying the structural adequacy of the glass is imperative. Given that this was done while maintaining the intention of table 2.1.1.1 of the SB-13, it is our view that using 8mm tempered glass is structurally adequate. Tempered glass thickness for Type RL T2.2 is to follow the latest approved shop drawings/documents for the different areas where it applies. It is our understanding that, as the SB-13 was a quick response to a situation involving glass failures in guards at the time of its composition, it is a common understanding in the industry that the 6mm maximum thickness requirement in table 2.1.1.1 of the SB-13 may have been an error in the table, due to the quick turnaround of SB-13 which was required at the time. Please note that the more recently published CSA A500-16 standard, "Building Guards", seeks to fix this error by removing this thickness requirement from the glass type table (table 6.1 ), intended for the same purpose as table 2.1.1.1 of the SB-13.

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