Prefab, Portable Green Roof Installed In Toronto


Green roofs keep buildings cool, control water runoff and can be really nice to look at, in those rare situations where there is office space overlooking terraces, like there were at ESRI Canada's Toronto offices. But what do you do in an existing building, when you are a tenant and not an owner?


That is one of the many problems that Alex Miller, President, ESRI Canada, and landscape architect Scott Torrance had to face. Others included access problems (the only road beside the building was a fire access route) Weight limitations (it is an existing building with occupied office space below the terrace) and the perennial issue in buildings: access window washing anchors.

Landlords don't appreciate tenants modifying their building, nor do they like a lot of disruption for the other tenants. So even though ESRI's landlord was very cooperative, they still had to design it prefab so that it could be installed quickly, and they laid it right on top of the existing roof slabs so that it can be lifted up and taken away with no damage to the existing building, if necessary. So calling it portable is a bit of a stretch, but it could be removed and reinstalled somewhere else if it had to be.

Untitled from Lloyd Alter on Vimeo.

I asked ESRI General Manager John Kitchen about the issue of being a tenant rather than an owner, and making such an investment in a property they didn't own. He explained that it was a wonderful amenity for the office, and created "a visually-stimulating and enhanced workplace environment that is expected to help improve productivity." -and that he wasn't going anywhere in a hurry.


They don't look like much, but those window washing tiedown rings in the gravel are a big issue. They are regulated by the province, one has to submit plans for approval when you build a building and revisions are tough. Scott Torrance designed all the planting so that the lines for the window washers go between them. The gravel also keeps people on roof away from the glass.

Scott Torrance explains the difficulties of building a green roof from Lloyd Alter on Vimeo.

Scott Torrance, the landscape architect of the project explains.


Another unusual design feature is the way it is broken into zones; ESRI didn't want people wandering all over the place and disrupting meetings, it is different up there on the ninth floor than it is at ground level where people walk by windows and offices have blinds. Scott created "outdoor rooms" that mirror the interior spaces.


A detail of the plan.


A view from the board room out to the board room's zone.


Because it is an existing roof, the depth of the soil is minimal, varying between four and six inches. This limits the variety of planting and the locations of heavier stuff, putting bigger loads over columns.

This video from ESRI shows some of the problems of installation; the entire roof was prefabricated and pregrown, then lifted up by crane over two weekends, so that the fire routes were not blocked during working hours.


Given the constraints and limitations, it is a pretty impressive.

More on Scott Torrance Landscape Architect

ESRI Canada

More green roofs:
Green Roofs Help Fill Buildings: Good for Business As Well as the Environment
Green Roof School Disappears into Hillside
Post Office Plants 2.5 Acre Park With Green Roof
Raising the (Green) Roof!!
Canada's Largest Green Roof

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