Temporary Demountable Event Structures
By Sasa Dzekic, M.Eng., P.Eng., September 2026
On Wednesday, September 2, 2026, Toronto and the wider Greater Toronto Area were hit by a severe thunderstorm system that produced heavy rainfall and large hail. Strong winds brought down numerous trees and utility lines and damaged structures. One of the most significant losses occurred at Rogers Stadium, located at the former Downsview Airport Lands in North York, Toronto. Rogers Stadium is a seasonal outdoor concert venue with grandstand seating and a capacity of 50,000. It was constructed in about nine months and opened in June 2025. Although the venue was planned for a multi-year operating period, it was built as a “temporary facility” rather than a permanent stadium, because the site was intended for redevelopment afterward.
The three grandstand structures were built with manufactured components that can be installed, modified and ultimately dismantled and removed. The largest (central) grandstand suffered significant structural damage in the storm. The other two stands will require evaluation for structural damage. Other smaller structures at the facility also suffered damage from the wind. The cause of the damage has not yet been established, and it would be premature to speculate on it.
Whatever the cause, the damage highlights a gap in Ontario's regulatory framework that has existed since it was written. The 2023 Building Code amendment on demountable stages, which came directly out of the 2012 Radiohead stage collapse at this same site, does not expressly cover demountable spectator stands. To understand why that matters, it helps to go back to 2012.
The Rogers Stadium incident fortunately did not result in personal injuries. However, it is a stark reminder of the collapse of another temporary structure at Downsview, which did result in a fatality. On June 16, 2012, a temporary concert stage for the UK rock band Radiohead was in the final stages of erection when its roof suddenly collapsed, just hours before the band was scheduled to perform. The concert was sold out, but the audience had not yet been admitted. Scott Johnson, Radiohead's drum technician, was killed, and three other crew members were injured. Radiohead subsequently cancelled the concert.
In the days and months that followed, several engineering teams investigated the Radiohead stage collapse. I took part in that work as a member of my former forensic engineering firm. The investigation was extensive. It involved an on-site examination of the collapsed structure (see the photographs below), recording the measurements and geometry of structural components, weighing the equipment and structural components, conducting structural modeling and analysis, performing joint expert testing at the McMaster testing facility, and reporting on the findings and opinions.
The stage support framing was a manufactured modular scaffold-like steel structure consisting of vertical tubes (standards), horizontal tubes (ledgers) with circular rosette rings. and diagonal tubes (braces) which locked securely into these rings using a wedge-and-pin mechanism. The system was first used in 1990, and was dismantled and re-assembled at different locations for many years.
Unlike several other stage collapses around the same period that were caused by extreme weather, the Toronto collapse occurred under clear weather conditions. The investigation found that the collapse resulted from significant shortcomings in structural design, construction and inspection.
A trial followed in 2015 and the Ontario Coroner’s Inquest into the collapse was held in 2019. The five-person inquest jury made 28 non-binding recommendations, including the creation of a group to develop and maintain standards and procedures for the live performance industry. The Radiohead case was not simply a lesson about designing a stronger roof. It was a lesson about controlling the entire lifecycle of a temporary structure. The engineering recommendations called for changes to the Building Code and the occupational health and safety regulations so that temporary structures would be designed by engineers and inspected by engineers before being put into use.
Professional Engineers Ontario subsequently developed its Design Evaluation and Field Review of Demountable Event and Related Structures Practice Guideline, which was published in March 2020. Ontario’s Ministry of Municipal Affairs and Housing established an Expert Advisory Panel on Outdoor Temporary Stages, which included engineers, stage builders/operators and municipal building officials. As a result, Section 3.16A “Demountable Stages and Demountable Support Structures,” an amendment to the Ontario Building Code (O. Reg. 30/23), was implemented in 2023.
There is an emerging trend toward larger and higher-capacity temporary demountable assembly structures. For example, a temporary grandstand expansion similar in type to the Rogers Stadium stands was recently constructed at BMO Field in Toronto for the 2026 FIFA World Cup. The existing permanent grandstands with a capacity of approximately 28,000 were expanded by adding two temporary spectator stands (north and south) with approximately 17,000 seats, for a total capacity of 45,000. The temporary seating was constructed in two phases (2024/25 and 2025/26). It was dismantled and removed after the World Cup in the summer of 2026. Both the BMO field and the Rogers Stadium grandstands were manufactured scaffold-like tubular steel demountable structures.
Of concern is a gap that exists in the scope of application of Section 3.16A, renamed to Section 3.17. in the current 2024 Ontario Building Code. The regulation's definition of a “demountable stage” is oriented toward performance platforms used primarily by performers and workers, while a “demountable support structure” is for supporting equipment such as lighting, sound equipment, banners and stage sets. Both types are intended to be “erected, assembled or installed for a limited specified time.” The underlying assumption is that they are temporary structures. Demountable grandstands supporting spectators during events are outside the scope of application above. They must still be designed by a professional engineer under the general requirements of Part 4 “Structural Design” of the Ontario Building Code. Whatever the investigation into the Rogers Stadium damage ultimately finds, large manufactured demountable grandstands now seat tens of thousands of people, and the regulatory framework built after 2012 has not caught up with them. The lesson of the Radiohead case applies here as well. The safety of a temporary structure depends on controlling its entire lifecycle, from design evaluation through erection, inspection, operation for a specified time, and dismantling, and not only on the strength of its components. That is where the regulatory processes for large temporary demountable grandstands need to be revisited and expanded, before rather than after a loss of life.