SA Roofing September 2017 // Issue: 93 - Page 22

FEATURES Genus Succulents are great plants to have on a roof garden. performance, biodiversity, climate or microclimate specific reasons. “Vegetables will be fine but require about 20cm of soil and more watering and maintenance,” says Greenstone. A green roof only requires between 2cm and 10cm of soil. For green roofs, plants are treated en-masse and are low growing making them more ecological. “There is a greater selection of plant species from the Genus Succulents (water storage plants),” Greenstone adds. Erich Mulder from Green Squared explains a pre-grow process that occurs inside the roof planter, which is done three to four months prior to installation. Growing the plants in a customised roof planter makes installation easier. “The planters are installed directly onto the high- density polyethylene (HDPE) layer,” he says. Depending on the design objective this determines what growing medium is used, the depth of the growing medium (this also affects the weight), irrigation required, fire hazards, waterproofing, root barriers, maintenance and so on. “In many cases one or more of these factors dictate or prohibit which plants can be used,” Ferreira says. 20 SEPTEMBER 2017 RESIDENTIAL // COMMERCIAL // INDUSTRIAL He also says that the most efficient plant type for green roofs are indigenous succulent ground covers that provide all required benefits as they are water efficient, self-seeding, have shallow root systems and do not require intensive maintenance. Locally there are no regulations, standards or guidelines on how to install a green roof, however, there are regulations for voluntary green-star related designs. Penetron says that these roofs shouldn’t leak therefore a drain