Ways to Install Green Roof Systems

Green Roof Technology

• Green roofs add layers of planting medium and plants on top of a roof system. The components of the green roof are a growing medium for plants and plant cover suitable for the climate installed on a waterproof membrane. Filtering and draining mechanisms are also necessary, and the underlying roof must be sealed against water, water vapor and roots. Several types of green roof technology for plant material are available: complete systems, modular systems and vegetative mats.

Complete Systems

• All the components in a complete system are designed for plant material. This system gives the most flexibility in the types of growing medium, drainage and protection layers, which influence the kinds of vegetation that can be supported. The thickness and weight of complete systems varies from 2 to 3 inches and 12 to 18 pounds per square foot. Several types of waterproof membranes can be used with complete systems.

Modular Systems and Pre-Cultivated Vegetation Blankets

• Modular systems are trays of plants grown off site and placed on the roof for full coverage; the depth of the growing medium ranges from 3 to 12 inches. Planting choices are limited in modular systems. A pre-cultivated vegetation blanket is an interlocking green roof tile often planted in 1 inch of substrate with several varieties of Sedum, a hardy ground-cover species. The blankets are cultivated at ground level and rolled and transported to the roof.

Design Considerations

• The use of the green roof is the primary consideration for making decisions about the type of system. Ensure the roof is structurally sound for green roof components and consider the desired function of the green roof, whether it's intended only for passive environmental benefits or as a social and aesthetic asset as well. Consider the structural capacity of the building, the extent of maintenance involved with the system and local regulatory requirements.