Products / Columbia Green Extensive Layered System

Columbia Green's Extensive Layered System is a lightweight built-up vegetative roof whose layers can be cut on site to fit curves and angles: a 15 to 16 mil Columbia Green root barrier, a 0.375 in drainage layer of entangled polypropylene matrix with a spun-bonded polyester filter fabric pre-attached, a 1.0 in high-loft polyester water retention layer, regionally sourced extensive growing media and low-growing sedum or ground covers. The technical sheet gives media depths of 3 to 6 in and saturated weights of 20 to 24 lb per square foot at 3 in, 26 to 30 at 4 in and 37 to 43 at 6 in (including 2 lb per square foot of plants); the web page summarizes the range as 20 to 39 psf. The maker says the airflow through the layers helps reduce the chance of uplift and that the system detains and retains rain and irrigation water.