Green roof by-law “Most people are sensible and plant trees in the ground.” —Ian Richie distinguished architect
Toronto was the first city in North America to have a by-law to require
and govern the construction of green roofs on new development. It was
adopted by Toronto City Council in May 2009, under the authority of
Section 108 of the City of Toronto Act.
The By-law applies to new building permit applications for residential,
commercial and institutional development made after January 31, 2010
and will apply to new industrial development as of April 30, 2012.
The By-law requires green roofs on new commercial, institutional and
residential development with a minimum Gross Floor Area of 2,000m2 as
of January 31, 2010.
Use the green roof screening form as a tool to determine quickly
whether you will be required to build a green roof. Details of the
requirements are provided below. The green roof coverage requirement is
graduated, depending on the size of the building. The table below shows
how the requirement ranges from 20-60 per cent of Available Roof Space
for commercial, institutional and residential development. Available
Roof Space is defined as the total roof area minus areas designated for
renewable energy, private terraces and residential outdoor amenity
space (to a maximum of two square metres/unit).
A tower roof on a building with a floor plate less than 750 square meteres is also excluded from available roof space.
Gross Floor Area *
(Size of Building)
Coverage of Available Roof Space
(Size of Green Roof)
2,000 - 4,999 m2
20%
5,000-9,999 m2
30%
10,000-14,999 m2
40%
15,000-19,999 m2
50%
20,000 m2 or greater
60%
* Note: Residential buildings less than six storeys or 20 metres in height are exempt from being required to have a green roof.
Toronto Becomes first city in North America to mandate green roofs HGTV
Posted by: Gary Butler (abridged)
19 April 2016
Toronto is well on its way to becoming Canada’s Emerald City, thanks to
a bylaw that requires green roofs on new construction. Residences,
commercial and institutional buildings over 2,000 square metres must
have a roof that’s 20-60 percent “living.” Green/living roofs are
partly or completely covered by vegetation, planted into a growing
medium and sitting over a waterproof membrane.
They often include structural support, irrigation and drainage systems, and can even incorporate greywater treatment ponds.
Green roofs have many benefits. They not only insulate the buildings
they shelter but also improve air quality and reduce runoff, easing
sewer system loads and preventing associated overflow. They cool in
summer, reduce heat loss in winter, and can support birds and other
wildlife. Where green roofs top public buildings, they create public
green space and parkland.
Living roofs can even help cool an entire city in the summer by
reducing what’s known as the “urban heat island effect,” where
traditional roofing and paving materials increase the overall
temperature of the air. scotttorrance.ca
Growing in popularity, green roofs can be installed on everything from
your own home to a giant arena. They have a long history — from the
Hanging Gardens of Babylon to sod houses in Scandinavia — but today’s
green roofs use modern technology for roofs that are clean,
low-maintenance and even useful (imagine growing vegetables and fruit
on the unused space just above your head).
The first city in North America to mandate green roofs, Toronto has
also been a leader in installing them, with 72,000 square metres of
green roof space created in 2014 alone — and permits pulled for 186,000
square metres!
