What depth of growing media is typical for intensive vegetated rooftops?

Intensive vegetated rooftops are designed to support a wider variety of plants, including larger shrubs and even small trees, which require a deeper growing medium to accommodate their root systems and overall growth needs. The typical depth for growing media in intensive systems ranges significantly, often between 6 inches to 4 feet. This range allows for proper drainage, water retention, and the necessary nutrient profile for healthier, more diverse plant life.

As the depth increases, it can support a greater range of vegetation and enhance biodiversity, crucial for urban green spaces. Additionally, deeper media allows for better stormwater management by retaining more water and aiding in the natural filtration process, which is essential in mitigating runoff and improving water quality.

In contrast, options that suggest shallower depths, such as 2-6 inches or 6-12 inches, are more aligned with extensive green roofs, where lighter vegetation, such as sedums and grasses, is commonly used. These plants require less media depth because of their shallow root systems and lower water, nutrient, and weight demands. The option of 1-2 feet, while it may seem appropriate, does not fully encompass the upper limit standard for intensive systems, thus making the specified range of 6 inches to 4 feet