WATERPROOFING:
Green
roofs do not replace the waterproofing. The Green Roof system is placed
on a waterproofing membrane. Plant roots are strong. They can permeate
into little cracks or seams. For that reason the roof membrane has
to be root protected. When the waterproofing is not root protected
an extra root barrier must be placed on top of the waterproofing.
This root barrier however, never reaches the quality of a root protected
waterproofing.

The choice
of the waterproofing is optional and can be anything from bituminous
membranes to PVC, EPDM or TPO. A fully bonded system is strongly recommended.
This will prevent water tracking beneath the waterproofing in the
event of damage to the membrane. This in turn minimizes the cost of
removing the Green Roof to carry out repairs.
Details such as flashing, parapets, drains, roof slope, roof penetrations
and types of insulation have to be adjusted according to the Green
Roof system used. These adjustments should be finalized before construction
of the roof commences. These details are the most critical elements
for durable waterproofing and Green Roof systems.