By Steve Kupferman

At a preview, on Monday afternoon, of City Hall’s new green roof, Chris Pommer stood in council chambers and explained some of the thinking behind the multicoloured carpet of vegetation that will soon engulf the podium area underneath Nathan Phillips Square’s iconic concave towers. Pommer is a partner at PLANT Architects, the firm that designed the new roof. The project was conceived as “an elaborate series of plantings,” he said, gesturing at a large architectural illustration full of minute detail. Elaborate plans are one thing, but we had to wonder just who was doing all this planting.
At thirty-six-thousand square feet, City Hall’s new podium roof will be the largest publicly accessible green roof in all of Toronto when it opens this spring. (It’s only about half-finished at the moment, but the City and its contractors were evidently anxious to show it off before winter.) In terms of area, the new living carpet will cover the equivalent of slightly more than half a football field.
It was a surprise to learn that the entire task of planting is being handled by a crew of no more than eight workers on any given day and sometimes as few as six.

Damon Dewsbury, a roofer with Flynn Canada, the company hired by the City to install the green roof, reckoned that each green roof worker lifts anywhere from six to eight thousand pounds of plants and soil during an average work day. Obviously, not all at once.
As we made the circuit around the windswept artificial meadow, Dewsbury showed us the one- by two-foot rectangular plastic containers the plants arrive in, soil and all, from their growing facility. The containers are part of a modular roofing system. Workers simply place them on the roof, like paving stones. The plants and soil don’t even have to be removed.
Each container, Dewsbury said, can weigh up to seventy-five pounds. And his job is to heft them, all day long.
The seemingly bucolic practice of green roofing is actually something of a contact sport.

The peculiar nature of the City Hall site adds another complication to the task of planting. Rod Undseth, another roofer, said that the rectangular plant containers each need to be carefully angled, so that they can mimic the curvature of the outer walls of City Hall’s towers with no gaps between them.
Once the containers have all been installed, workers will yank out their removable plastic side walls to allow the soil and plants within to merge into a continuous whole. The plastic sides are then saved for reuse in future green roof installations, according to a Flynn Canada manager.
Dewsbury, Undseth, and their colleagues have been at work on the green roof since mid-April and will continue working until mid-November of this year.
Their services will be in high demand after January 31, 2010, when the city’s new green roof bylaw comes into effect. The bylaw will require all new commercial buildings with floor plans in excess of two-thousand square feet to have green roofs. In 2011, similar requirements will come into effect for new industrial buildings.

City Hall’s green roof is, in effect, the city’s way of leading by example. The architects and politicians behind the project are enthralled with the site’s potential as a new public gathering space (there will eventually be paths, benches, and tables) and as an energy-saving measure.
It could well turn out to be both those things, but presently it’s a work in progress. With an emphasis on “work.”
Photos by Michael Chrisman/Torontoist.