Which type of vegetated roofing system requires a minimum soil depth of one foot?

Intensive vegetative roofing systems are designed for more complex planting strategies and can support a wider variety of plants, including shrubs and small trees. This type of roofing typically requires a minimum soil depth of one foot to accommodate the root systems of these larger plants, as well as to provide adequate water retention and overall plant health. This depth allows for greater biodiversity and a more robust ecosystem compared to other systems, such as extensive vegetative roofing, which usually utilizes shallower soil depths and is limited to smaller plants and sedums. Intensive systems are often used for recreational spaces and gardens on rooftops, further necessitating the need for deeper soil to support these uses effectively.