Green Rooftops
Green roof systems are vegetated covers of growing media and plants taking the place of bare membrane, gravel ballast, shingles or tiles. The number of layers and the layer placement vary from system to system and green roof type. However, all green roofs include a single to multi-ply waterproofing layer, growing media and plants, with drainage covering the entire roof deck surface. There are two main types of green roofs -- extensive or intensive -- although a green roof can be designed with features of both.
The roof function or objective of the roof space determines the design -- an ecological cover or for human recreation, vegetable gardening, etc. The factors for green roofs include: the roof loading capacity or maximum dead and live weight loads (as determined by a structural engineer), the slope of the roof, and perhaps the client’s budget.
Extensive or Eco-Roof
Extensive – OR eco-roofs, and low-profile, have thinner and less numbers of layers, therefore they are lighter, less expensive and very low maintenance. Extensive green roofs are built when the primary desire is for an ecological roof cover with limited human access.
The minimum growing media or soil substrate starts at about 2 1/2” to 6” at most...
Intensive
Also referred to as high-profile, look like traditional roof gardens because a much wider variety of plant material can be included since growing media depths are increased.
The growing media starts from about 8 - 12” and can range up to 15 feet or more, depending on the loading capacity of the roof and the architectural and plant features that the building owner desires. The engineered soil media usually contains...
Semi-Intensive
Typically used in plantings of 4"-6" Semi-intensive mixes the structure of intensive and the lighter weight properties of extensive.