Print this page

Green Roof Solutions

Three basic vegetation solutions exist for green roofs: extensive, semi-intensive and intensive. Lightweight, low-maintenance extensive or semi-intensive roof solutions can be used to install a long-lasting green roof on all types of roof (including steep-pitched roofs).

Properties of the Main Types of Green Roofs

Criteria Extensive Green Roof Semi-Intensive
(roof garden)
Roof frame support3  concrete  concrete
Plant mix Sedums, moss, perennials Perennials, small shrubs, lawn Shrubs, trees, lawn
Substrate thickness 2" to 6" (4 to 15 cm) 5" to 12" (12 to 30 cm) 12" (30 cm) or more

Weight of full system

15 to 37 lbs/sq. ft.
(75 to 180 kg/sq. m.)
41 to 102 lbs/ sq. ft.
(200 to 500 kg/sq. m.)
102 to 410 lbs/sq. ft.
500 to 2000 kg/sq. m.)
Watering no* plant plant
Maintenance hand handhandhand handhandhandhand
Roof Cost $ $$$ $$$$
Accessibility Often inaccessible Limited Highly accessible


Green Roof Assembly

The roof assembly requires standard insulation and a waterproofing system in which the waterproofing membrane is either resistant to penetration by roots, or is reinforced with a root barrier layer. Thermal insulation, generally installed underneath the membrane, completes the roof's technical structure.

HYDROPACK--water-evacuationA green roof system consisting of four layers, each with a specific purpose:

  • The drainage layer enables excess water to drain away, preventing root asphyxiation
  • The filter layer traps fine particles from the substrate to prevent the drainage layer from becoming clogged
  • The substrate layer serves as an anchor for roots and supplies water and minerals to the plants
  • The vegetation layer, consisting of species suitable for rooftop conditions, reintroduces nature to our urban landscapes