Abstract:
Extensive living roof substrate design to promote storm water management while balancing structural load and maintaining ≥ 60% non‐irrigated plant cover is investigated through linked laboratory and field experiments in Auckland, New Zealand. Setting quantifiable goals for FLL (2002) and agronomic testing methods resulted in successful design of multiple non‐proprietary substrates. Particle size distribution and quality control in the materials' supply chain are critical. Additional work is required to define a meaningful standard permeability test for living roofs. While the FLL (2002) maximum water capacity provides a conservative estimate for structural loading when a substrate is wet, it should not be used to predict storm water retention. Agronomic measures of readily available water (10–100 kPa suction) plus plant stress water (100–1500 kPa suction) provide a reasonable estimate for the maximum potential rainfall storage during individual storm events. Subject to Auckland's frequent rainfall, an extensive living roof with 70% v/v 4–10 mm pumice, 10% v/v 1–3 mm zeolite, and 20% organic matter at 100 mm depth is recommended to maintain plants without irrigation (excluding drought conditions) and minimize weeds while preventing runoff from storms with less than 25 mm rainfall.
