It is the task of the designer to make adjustments in the green roof system accordingly e g.
Low pitch green roof.
For a green roof installation that pitch should be at least inch per foot of run.
If not properly secured a pitched vegetated roof can erode and slip under heavy rain excessive irrigation or poor plant growth.
Above 5 degrees roofs are considered to have a pitch which may affect the design.
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.
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.
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.
Sloped roofs retain less water in general and the moisture content varies from the ridge to the eave lowest edge of the roof.
Most vegetation will grow on quite sever slopes but the designer must consider the practicalities of installing the green roof and just as importantly how the roof is to be maintained.