While not as common for retrofits, intensive green roofing is still an option, particularly for new buildings or buildings that will need a completely new roof. This method allows for greater use of the roof, more plant options and better drainage.
An intensive green roof is designed to hold roughly 150 pounds of vegetation per square foot. They are cultivated and tended like a garden, so while it can support larger plants and trees, you’ll also want to consider the long-term maintenance of the roof.
When creating an intensive roof, the drainage system needs a great deal of thought and planning. A pitch is laid beneath the vegetation to help direct any excess rainwater to the drains.
Beneath the drainage system, you have several options for waterproofing, insulating and vapor management. Keep in mind that an intensive green roof uses more soil, so it won’t need the same insulation as other types of green roofs. It will, however, need waterproofing.
After ensuring you have proper water management in place, up to 20-inches of soil or growing medium is added to the roof, followed by the plants and trays. This method does take longer to get started and for the plants to grow, but it will produce the most customizable results.