The Best Most Light Weight Growing Medium For Green Roofs

Green roof substrate has been researched developed blended and improved over several decades.

The best most light weight growing medium for green roofs.

These aggregates make a good basis for a growing medium. Now comes the growing medium which for a sedum roof should be at least 8cm 3in deep and for a roof of wildflowers herbs salad and strawberries at least 15cm 6in deep. Because they absorb water sedums are commonly used on green roofs. Extensive green roofs have a growing depth of 3 to 6 inches and are typ ically lighter in weight with a saturated weight of 15 to 30 pounds per square foot.

Pumice is somewhat porous and is lighter than most aggregates. Depending on the plants grown most will perform best in a blend of a peat based growing medium with lightweight clay aggregates coir chunk or heavier material to help support the plant throughout one or more gardening seasons. For the best green roof medium the growing media should contain the following. This of course can be reflected in the cost of building materials.

An all purpose soil less peat free potting mix is fine for growing herbs and other edibles but mix in plenty of perlite to both improve drainage and save on weight. Lightweight volcanic aggregate such as pumice or lava. Furthermore they are drought and wind tolerant. In general the bulk of the water storage in a green roof buildup is in the growing medium.

These materials are available throughout the west coast of north america. Furthermore it should be made up of a blend of materials that is not too heavy for a roof to support. To display the best plants for green roofs and to trial untested plants for their. Over a 100m2 green roof with 10cm depth of growing medium the weight saved by using substrate instead of soil is considerable.

The extension includes high quality waterproofing a root repellent system a drainage system filter cloth and a lightweight growing medium and plants. When installed the sedum blanket including the 20mm of growing medium is rolled out onto either 50mm 70mm of growing medium standard method or directly onto a moisture retention blanket ultra light weight method. Cally described by the depth of the growing medium extensive semi intensive and intensive. However the factors allowing for a lightweight roof can create a high stress environment for plant material.