Several considerations must be reflected upon in the development of a green roof…
Structural requirements depend on the type of roof constructed as well as environmental conditions…
This topic is divided as follows:
Dead load (D)
The weight of the building medium, stationary and any permanent materials of construction.
Live load (L)
The load to be produced by the intended use of a green roof, such as the soil medium and vegetation, as well as snow, ice and rain.
Wind load (W)
Temperature load (T)
For greater live load (e.g. intensive roofs, climate variable) there has to be greater dead load, hence greater capital cost.
It is best to get a structural engineer to determine what your existing roof needs to support the weight of a green roof.
Green roofs generally consist of multiple layers which provide a growing surface and drainage of excess water.
More specifically, these layers can include:
Vegetation – or plant – layer
Soil filter fabric
It is imperative that water not absorbed by the roof is drained properly so the installation of the geomembrane is of utmost importance
Leak test is performed as follows:
Top the first layer of the geomembrane with one or more thin sheets of foam insulation suited for contact with damp soil.
Following, set a drainage mat with capillary spaces on top of the insulation. Place the mat so the felt side faces up in order to keep the soil from clogging the mat.
Above the drainage mat, place a soil filter fabric that serves as a root barrier.
You can frame the sides for the roof with mesh gutter guards, wood or other edging that will permit drainage to hold soil in place.
Add the soil medium
Add the vegetation layer