BCAB #1364 - Structural Design of Glass Guardrails, Articles 18.104.22.168., 22.214.171.124., 126.96.36.199. & 188.8.131.52.
September 16, 1994
Re: Structural Design of Glass Guardrails, Articles 184.108.40.206., 220.127.116.11., 18.104.22.168. & 22.214.171.124.
The project in question is a new single family dwelling. The guardrail around the attached sun deck is constructed of laminated safety glass and has no top rail.
Reason for Appeal
This appeal results from a disagreement over whether or not a top rail is required on the glass guard.
The appellant contends that a top rail is not required for the glass guard. Part 9 does not specify any loads for guards and although CAN/CGSB-12.20-M,Structural Design of Glass for Buildings, requires a top rail for glass guards, this standard is only referenced in relation to windows (Article 126.96.36.199.). Further, the appellant contends that if CAN/CGSB-12.20-M were applicable, its requirement for a top rail...continuous over two or more lights... is based on the assumption of sudden failure of plate or tempered glass and laminated glass will assure progressive failure with adequate warning and the glass will remain in place until replacement and repair is done.
Building Official's Position
The building official maintains that a guard is a structural member and must be designed in conformance to Part 4, Article 188.8.131.52. If a guard is made of glass it must be structural glass and the only reference to structural glass is Article 184.108.40.206. which calls up CAN/CGSB-12.20-M. This standard specifically addresses guards and requires a top rail. Laminated glass has failed when it breaks and deflects even though it may remain in place.
Appeal Board Decision #1364
It is the determination of the Board that CAN/CGSB-12.20-M,Structural Design of Glass for Buildings, is not applicable to the glass guard in this Part 9 building because it is only referenced in Part 9 in relation to windows (Article 220.127.116.11.). Therefore, the requirement in this standard for a top rail on a glass guard is not applicable.
However, for a guardrail to act as a protective barrier to prevent accidental falls as described in the definition of guard it must be structurally designed to resist expected loads. The Appendix note to Article 18.104.22.168. clearly supports this determination and indicates that guards can be accepted based on experience or structural design. Structural design criteria is contained in Article 22.214.171.124.
George R. Humphrey, Chair