You Bet Your Glass: October 2012
By Frank Fulton
Code toughens up balcony glass
By Frank Fulton
In the June issue of Glass Canada, You Bet Your Glass discussed the
matter of spontaneous breakage and falling glass from balconies in
highrise apartment buildings.
In the June issue of Glass Canada, You Bet Your Glass discussed the matter of spontaneous breakage and falling glass from balconies in highrise apartment buildings. The primary culprit for the failures was determined to be nickel sulphide inclusions or impurities in the tempered glass lites, which shrink during the tempering process and expand over time, resulting in exploding glass in some cases. Although there are known to have been at least 30 incidents of shattered balcony glass falling from buildings in Toronto alone during the past year, fortunately there have been no significant injuries to pedestrians.
In response to requests from the City of Toronto and the Residential Construction Council of Ontario to amend the Ontario building code to address the falling balcony glass panel problem, the Ontario Ministry of Municipal Affairs and Housing established the Expert Advisory Panel on Glass Panels in Balcony Guards. The panel was composed of 25 members, including engineering consultants, building code consultants, developers, contractors, professional designers, municipal building inspectors, insurance providers, and members of codes and standards writing bodies.
Based on the panel’s recommendations, the ministry issued Supplementary Standard SB-13 to amend the Ontario building code, setting higher standards for design as well as the types of glass to be used in balconies for all highrise developments approved after July 1, 2012.
In addition to prescriptive requirements to ensure that glass does not come into contact with the metal railing members, and clarification of live and guard load structural calculation procedures, the significant changes focus on the type of glass that can be used on balconies in the future.
Balcony glazing located beyond the edge of a floor, or within 50 mm of the edge of a floor, shall be heat-strengthened laminated glass. Glazing located from 50 to 150 mm inward from the edge of a floor shall be fully heat-soaked tempered glass or heat-strengthened laminated glass. Glazing located more than 150 mm inward from the edge of a floor shall be heat-strengthened laminated glass, heat-soaked tempered glass, or standard tempered glass (not heat-soaked) as long as it does not exceed six millimeters in thickness. (The probability of having nickel sulphide inclusions is higher in heavier glass.)
These regulations are now the toughest in Canada, though they are not retroactive and do not apply to existing buildings. However, the measures made to Ontario’s building code are only temporary. The province has asked the Canadian Standards Association to develop national guidelines that could then be adopted under Ontario’s code. The standard-writing process is underway and is expected to be completed within the next few years. At that time, it is reasonable to assume that the standard will be referenced in the National Building Code of Canada, and that these more stringent glazing directives will be applied nationwide.
From the glass industry perspective, the question now is how these code changes will impact the use of glass in balconies in the future. In addition to most of the glazing now having to be heat-strengthened and laminated, the railings, posts and anchorage must also be made stronger and heavier to withstand increased structural loads. The increase in cost to developers for the “improved” glazed balcony systems could bring the overall cost to more than $10 per square foot.
According to Mark Brook of BVDA Facade Engineering (who is one of the members of the Expert Advisory Panel and involved as a consulting engineer on numerous highrise buildings), the changes to the building code have not had much impact on the demand for glazed balconies thus far. “Many developers had started using laminated balcony glass as a safety measure prior to the code changes.”
Frank Fulton is president of Fultech Fenestration Consulting. He has been in the industry for 30 years and can be reached via e-mail at firstname.lastname@example.org.