Nathan Phillips Square

City Hall's Podium Green Roof

City Hall's Podium Green RoofFrom concrete to living garden, the Toronto City Hall podium roof, where visiting dignitaries were once welcomed at the “front door” of the Council Chambers, has been reopened as a public green roof garden.

Approximately 3,250 m2 (35,000 square feet) of concrete on the podium roof has been transformed into living vegetation to reduce the building’s environmental impact and for residents and visitors to enjoy all year around.

New landscaped gardens, courtyards, terraces, furniture and walkways provide unique views of downtown from this urban oasis in the heart of the city.

Come see how Toronto’s iconic City Hall continues to inspire in this age of environmental sustainability with its green roof structure that comes with a state-of-the-art irrigation system, and is also the city’s largest publicly accessible green roof!

City Hall's Podium Green Roof

As well as performing regular, state-of-good repair on the City Hall roof membrane, as part of the Nathan Philips Square Revitalization Project the City has installed an extensive green roof with 3,250 square metres (35,000 square feet) of vegetation).

The podium roof has been planted with a pre-vegetated, modular green roof system.

Modular systems are essentially trays of vegetation in a growing medium that are grown off-site and seamlessly installed on rooftops.

A diversity of plant species, grown regionally, has been selected for the City Hall podium roof for their seasonal colour and ability to withstand difficult rooftop conditions.

As part of the Nathan Philips Square Revitalization Project, the City has installed an extensive green roof with approximately 3,250 m2 (35,000 square feet) of vegetation on the podium roof of City Hall.

A diversity of plant species, grown regionally, has been selected for the City Hall podium roof for their seasonal colour and ability to withstand difficult rooftop conditions.

The podium roof has been planted with a pre-vegetated, modular green roof system that is essentially trays of vegetation in a growing medium, which have been grown off-site and seamlessly installed on the rooftop.

This system offers several benefits to this project over other technologies. The pre-planted trays were assembled on the finished roof assembly with the plants already established, making for a “finished” looking roof from day one. The units were designed for rapid assembly, shortening installation time.

Once in place, the top portion of each tray was removed exposing 2 to 4 inches of soil, allowing the plants to spread roots between trays, making a unified field of plants, and tying together the entire system.

Over the life of the roof, if roof maintenance is required, individual trays can be lifted off the membrane, repairs completed, and the plants put back in place, with little disruption to the plants themselves.

The plants for the Podium Roof Garden are a mix of various species of sedum and taller bulbs, perennials, and grasses, which are composed in East-West "drifts" of colour and shade tolerance, ranging from yellows and oranges at the sunny Southwest to purples and reds at the shady Northeast.

The garden is a mix of sun and shade tolerant sedums and perennials grown in a modular pre-vegetated tray system. The species range from grasses such as Feather Reed Grass and Little Bluestem to flowering Coneflower and Asters. All planting is united by a sedum mix ranging in colour from blue to green to burgundy. The trays are arranged in linear fields of purple, pink, yellow/orange and green, which correspond to the varying site conditions of full sun to shade and will change colour seasonally in this dynamic landscape.

The main planting areas ring the City Hall towers, with a paved courtyard framing the Council Chamber and an open, paved terrace at the Southeast. A circular tree planter featuring three Kentucky Coffee trees and aromatic shrubs provides shade and seating for the terrace that serves as a public gathering area.

A series of stone walkways around the perimeter completes the composition, along with smaller East-West connecting pathways running through the gardens.

On May 29, 2010, the City of Toronto officially opened the new publicly accessible rooftop garden at City Hall for residents and visitors to enjoy.

From concrete to living garden, the City Hall podium roof, where visiting dignitaries were once welcomed to this great city, revived and re-introduced as the new Podium Green Roof - Toronto’s largest publicly accessible green roof.

Included in this new urban oasis in the heart of the city are landscaped gardens, a courtyard framing the Council Chamber, a podium terrace and new walkways, to be enjoyed by residents, visitors and downtown workers.

Approximately 35,000 square feet (3,250 m2) of concrete will be converted to living gardens providing many benefits for the city as it strives to be one of the greenest on the planet.

Benefits of a green roof on the podium of City Hall:

  • Creates a new public garden for downtown Toronto;
  • Contributes to Toronto's green spaces;
  • Increases habitat for insects and birds in the heart of the city;
  • As part of the site-wide stormwater management system, reduces stormwater runoff, which affects the quality of local water resources that supply drinking water, are used for swimming, and serve as fish and wildlife habitat;
  • Improves thermal and sound insulation at City Hall;
  • Improves air quality and reduces the building’s contribution to the urban heat island effect and associated cooling costs;
  • Increases the lifespan of City Hall’s roof membrane by reducing thermal contraction and expansion;
  • Beautifies Toronto's premier centre for local government and democracy; and
  • Achieves a major recommendation of Toronto's Green Roofs Strategy – Making Green Roofs Happen (February 2006), which is to demonstrate leadership by installing green roofs on City-owned facilities.

News Archive

ExpandDec 6, 2006 - Finalists named in Nathan Phillips Square Revitalization Design Competition

Four outstanding design teams have been selected as finalists to compete in Stage II of the international competition to revitalize Nathan Phillips Square. The four teams short-listed by the competition jury to proceed to Stage II of the competition are:

  • Baird Sampson Neuert Architects, Toronto, with VLAN Paysages (landscape architect, Montreal); Halcrow Yolles (structural engineer, Toronto); Cobalt Engineering (mechanical engineer, Toronto); and Mulvey & Banani International Inc. (electrical engineer, Toronto)
  • Plant Architect & Shore Tilbe Irwin, Toronto, with Shore Tilbe Irwin & Partners (architect, Toronto); Peter Lindsay Schaudt Landscape Architecture, Inc. (landscape architect, Chicago); Adrian Blackwell (design collaborator, Toronto); Blackwell Bowick Partnership Limited (structural engineer, Toronto); and Crossey Engineering Ltd. (mechanical and electrical engineers, Toronto)
  • Rogers Marvel Architects, Ken Smith Landscape Architect, duToit Allsopp Hillier, New York, with Ken Smith Landscape Architect (landscape architect, New York) and Buro Happold (structural, mechanical and electrical engineers, New York)
  • Zeidler Partnership Architects, Toronto, with Group Signes (landscape architect, Paris, France); Halcrow Yolles (structural engineer, Toronto); and Hidi Rae (mechanical and electrical engineers, Toronto)

Stage II finalists will submit detailed design plans by February 16, 2007. A public exhibition of the final designs will be held before the jury meets in early March 2007 to evaluate the designs and select a winner.

For additional information, please see the news release announcing the four finalists.

ExpandOct 20, 2006 - Competitor's Materials

Please note that minor revisions have been made to the following material:

A. Competition Brief

  • Page 3 Sub-section 6.1: P1 Level Plan (Drawing A-1), Podium Level Plan (Drawing A-3) Sub-sections 6.3.4, 6.4.1, 6.4.10, 6.4.11, 6.4.13, 6.5.4, 6.7, 11.2 and 11.9
  • Figures and Drawings

B. Figures and Drawings

  • Survey Plan Nathan Phillips Square A-1 City Hall Basement and Parking Level 1 A-2 Site Plan
  • A-3 Podium Level

C. Supplementary Reports

  • Nathan Phillips Square Design Competition Transportation Study, September 2006 (Revised), IBI Group
  • Pages ii, 10, 17, 18, 19, 23, 25 and 31

Competitors should disregard previous versions of this material and refer to the revised material that is now available on this website.

ExpandOct 13, 2006 - Design Competition Brief

The Nathan Phillips Square Design Competition Brief, some Figures and Drawings and some Supplementary Reports are being revised. Competitors are encouraged to view the material currently available on this webpage. Revised material will be available the week of October 16, 2006.