Quality criteria – Substrates for green roofs
RAL-certified granular drainage material
Granular drainage material is defined as mixtures of graded, purely mineral-based material that absorbs excess water from the vegetation support layer and drains it into the guttering. The material can store water to a limited extent and allow roots to grow through it. Gütegemeinschaft für Substrate und Pflanzen e.V. inspects the material to assure quality.