Intensive and Extensive Green Roof Media: What does it all mean?
We often get questions about two common terms related to Green Roof Media (soil like substance): What is the difference between extensive and intensive soils?
Extensive media is designed to be used in applications off 6 inches of depth or less. It tends to drain at a high rate and has lower organic matter. It is tailored toward sedum plants that do not like wet roots or standing water. It tends to be rockier and lighter than other mixes. Naturcycle makes a variety of weights and variations on this blend
Intensive media is designed to be used in applications 6 inches or greater of depth. While supporting a wide variety of plants like grasses, trees and shrubs even. It tends to have a sandier texture, with a lower infiltration rate relative to an extensive blend. It is a denser more soil like media. Naturcycle has Intensive media varying in weight from 95 to 65lbs when saturated.
It is often asked: Can I substitute one for the other, meaning can I use Intensive in place or extensive or vice versa? Well you really cannot replace intensive with extensive but you can often use intensive in place of extensive. To simplify a project where sedum and planters are present. In reality some intensive media can be used under sedum mats or other applications in place of extensive. Most intensives drain fast enough to support sedum and can be made with a little less organics. You may want to adjust the soil depth (down actually say 3 inches of intensive vs 4 of extensive) to address water holding and flow. Some plants seems better adapted to this solution like pre-grown mats verse plugs or other shallow blends. It should be evaluated on a case by case basis but it something to consider in value engineering a project.
Pictured is an intensive planter and lawn combination in Somerville, Massachusetts