Nathan Phillips Square, Toronto, Ontario, Canada
Green roof size: 118,403 square feet
Award recipient: PLANT Architect Inc. & Perkins + Will Canada (architect/landscape architects) Project Team
Client: City of Toronto
Design team collaborator: Hoerr Schaudt Landscape Architect; Adrian Blackwell Urban Projects
Green roof designer and contractor: Flynn Canada / Gardens in the Sky
Green roof system: LiveRoof
Mechanical/electrical engineer: Crossey Engineering Ltd.
Heritage consultant: Blanche Lemko van Ginkel
Soils consultant: Urban Trees + Soil
Structural engineer: Blackwell Bowick Engineering

The Podium Green Roof Garden is the first transformation in the “Agora Theatre” scheme to revitalize National Phillips Square. The three-acre upper-level component of Viljo Revell’s 1965 City Hall and multi-level public square was originally conceived as a ceremonial public space, reached via a giant sculptural ramp. However, the concrete space was never successful at attracting the public and has been closed for over a decade.

The Podium Roof Garden re-conceives the upper level as a vast public park integrated with an existing elevated walkway system, reopening it to the public as an engaging 21st-century space. The goal is to reconsider how an extensive 4-in. to 6-in.-thick green roof can be a and successful public space providing space for gathering, strolling, and wandering within a complex and abundant variety of color and texture that merits repeated visits. It is the largest publicly accessible green roof in Canada and the flagship green roof project for the City of Toronto.

The park consists of a sedum and perennial mosaic perimeter garden, a sparkling black granite-paved courtyard that frames the Council Chamber, and a café deck that occupies the prow. The project's tray system allows for easy installation, and facilitates future maintenance. The varying depth of the trays is concealed to provide a seamless surface of planting.

A half-kilometer walk through the Garden reveals the passage of time at different scales. Shade structures mark the movement of the sun and the progression of plant and blossom colors, including something new blooming in different parts of the garden from April to October, marking seasonal change. The initial planting layout is deliberately linear, but the plants will shift and move over time.

The project brings new potential to the building and space by offering a garden respite from the harsh concrete downtown environment with places for intimacy and lingering, for lunch and evening strolls, for art installations, and to technically improve the building and environment by contributing to energy efficiency, roof membrane longevity, sound insulation, filtration, stormwater management, and habitat creation.

Steven W. Peck is the founder and president of Green Roofs for Healthy Cities, the non-profit industry association with a mission to develop the green roof and wall industry across North America. For more information visit Readers are invited to join GRFHC at CitiesAlive to meet the award winners and learn more about these outstanding green roof and wall projects: