Architectural zinc roofing considerations

A steeply sloped, zinc-clad roof is the architectural focal point of a new, open-air pavilion at the Trillium Park and William G. Davis Trail at Ontario Place in Toronto. The opening of the park and waterfront trail marked the first milestone of the province’s plan to revitalize and transform the iconic landmark into a vibrant, year-round attraction.

Approximately 600 m² (6458 sf) of proprietary blue-grey zinc, double-lock standing seam panels clad the four sections of the steep roof. The 0.8 mm (31 mils) zinc panels included a factory-applied backside coating, which reduces corrosion arising from design, construction, and workmanship defects. This coating frequently is used for standing seam and interlocking tile roofing applications.

The panels were installed by Semple Gooder Roofing Corporation in Toronto.

“The steep pitch of the roof, as well as some complicated intersections of panels, was definitely a challenge,” said Peter Sjourwerman, manager of Semple Gooder’s architectural cladding division. “But we have been working with zinc for more than 20 years and can pretty much fabricate anything. For example, we custom-fabricated a radius ridge cap with concealed fasteners for the pavilion in our shop and made all of the custom flashings onsite.”

Sjourwerman is a believer in zinc as a long-lasting material.

“It may last more than 100 years, but it definitely needs to be installed properly,” he said.

Design for Trillium Park was led by landscape architects LANDinc of Toronto in consortium with a diverse multidisciplinary team, including West 8 of New York and Blackwell Structural Engineers of Toronto.

“The pavilion sits at the end of a performance lawn as an object in space that is meant to create some curiosity and wonder and be a potential meeting place for small events and gatherings,” said Patrick Morello, principal of LANDinc.

Bruce Gilchrist, project manager and designer with LANDinc, continued, “No material other than zinc was considered for the roof of the pavilion. We sought out zinc for its naturally weathering patina, which will develop over time.”

The park pavilion’s design also included the use of heavy timber to reflect the industrial connections to natural materials at the turn of the 19^th century. An ongoing challenge was to sustain an open gathering space within the pavilion amid the wind forces imposed on the roof faces from Lake Ontario.

“LANDinc architect-of-record Christopher Wallace explored numerous structural options to achieve a limited number of columns that connect to footings embedded in bedrock,” Gilchrist said. “Due to the intersecting roof forms created by Adriaan Geuze of West 8, the greatest challenge was co-ordinating the work of each trade at the connection points. A virtual and physical 3D printed model was constructed by LANDinc and further evaluated to assist in the fabrication of each material section on the structure.”

Construction of the pavilion was completed by A-Con Construction of Bolton, Ont., working under Toronto-based general contractor (GC) Urbacon. The project team’s design and construction to revitalize Trillium Park and William G. Davis Trail at Ontario Place has received numerous accolades, including a 2018 National Award of Excellence from the Canadian Society of Landscape Architects (CSLA).

The opening of the park was the result of a three-year design consultation process, which included public workshops and consultations. The high-profile project was managed by Infrastructure Ontario and the ministry sponsored by the tourism, culture, and sport ministry.

At the opening celebration, the then minister of tourism, culture, and sport, Eleanor McMahon remarked, “This new public park and trail brings the beauty of Ontario’s natural landscapes to the heart of downtown Toronto. In a city this size, it is important to have resources like this one for people to enjoy.”

William G. Davis, former Premier of Ontario (1971–1985), added, “I am pleased to see a new era begin for Ontario Place and I am honoured by the beautiful trail that now bears my name. When Ontario Place opened in 1971, it was designed to be a place that everyone in the province could enjoy—a place that would show Ontario’s potential. Forty-six years later, that potential is our reality—a province that is inclusive, innovative, and a place that people from around the world are proud to call home. Once again, Ontario Place will be a gathering spot for the people of this province to come together.”