Before you initiate a green roof installation, you will need to know the
slope, the structural loading capacity, and existing materials of the
roof, as well as the nature of any drainage systems, waterproofing, and
electrical and water supply in place. You should also consider who would
have access to it, who will do maintenance, and what kind of sun and
wind exposure the roof gets.
Plant selection depends on a variety of factors, including climate, type
and depth of growing medium, loading capacity, height and slope of the
roof, maintenance expectations, and the presence or absence of an
irrigation system. A landscape architect would be able to advise you on
suitable plants and design of the plantings. (See the landscape contacts
below.) Here in California,
Rana Creek is the
leader in green roof systems and design.
The cost of a green roof varies considerably depending on the type and
design factors. As a budgetary figure, a green roof may be installed for
$12.00-$24.00 per square foot. While this might seem expensive, it also
reduces the need for additional insulation, and protects the real roof
The biggest obstacle in adding green roofs to smaller projects is the
added weight they create. As a rule of thumb, a green roof weighs the
same as water, 300 pounds per cubic foot. The additional weight might
require additional roof structure, and therefore, additional cost.
A final issue to consider in looking at a green roof system is how other
functions like photovoltaic solar panels could make better use of a
particular roof space.
When installed, green roofs provide a beautiful and environmental
alternative to traditional roofing. By knowing the considerations, you
will be able to choose an appropriate solution.