If not properly secured a pitched vegetated roof can erode and slip under heavy rain excessive irrigation or poor plant growth.
Low pitch green roof.
Above 5 degrees roofs are considered to have a pitch which may affect the design.
The most crucial component of any sloped green roof is the confinement system which holds the growth medium in place during the roof s early stages of development.
Even a flat roof should have some pitch so that it sheds water toward gutters.
It is the task of the designer to make adjustments in the green roof system accordingly e g.
Green roofs lower surface temperatures often by 50 degrees fahrenheit or more.
Before the plants go up a structural engineer should check to ensure that the roof can support the weight of the engineered growing medium and plants.
For a green roof installation that pitch should be at least inch per foot of run.
Sloped roofs retain less water in general and the moisture content varies from the ridge to the eave lowest edge of the roof.
In retrofit projects a sub framing system is attached to the existing flat roof surface to provide a minimum 12 roof pitch.
Drainage thickness of growing media plant varieties etc.