Low Pitch Green Roof

In retrofit projects a sub framing system is attached to the existing flat roof surface to provide a minimum 12 roof pitch.

Low pitch green roof.

Even a flat roof should have some pitch so that it sheds water toward gutters. Green roofs lower surface temperatures often by 50 degrees fahrenheit or more. 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. Sloped roofs retain less water in general and the moisture content varies from the ridge to the eave lowest edge of the roof.

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. Above 5 degrees roofs are considered to have a pitch which may affect the design. Moreover low slope metal roofs are not prone to the degradation experienced by organic materials enabling these roofs to better resist the elements. For a green roof installation that pitch should be at least inch per foot of run.

It is the task of the designer to make adjustments in the green roof system accordingly e g. Drainage thickness of growing media plant varieties etc.