● A built-in-place system is installed one layer at a time. System depth can be as thin as 2 inches and up to 3 feet or more. A built-in-place system can support sedums or can be designed to create a productive vegetable garden, a native habitat for migratory birds and butterflies, a meditative and play space, or any other imaginable landscape. System components depend on the design goals, though they often include a root barrier, protection fabric, drainage layer, filter fabric, growing media, and plants.

● A modular system is a series of trays that are each fully-contained green roofs. Trays have between 2 and 6 inches of growing media, though most often 4 inches, generally support sedums, and are not intended for human activity. Trays are often 1’ x 2’, depending on the supplier, usually have an internal drainage system and are typically filled with growing media and planted before they are delivered to the roof.

The roof shown was first built in 1872. The waterproofing was covered in sand and gravel to improve the insulation of the machinery operating within the facility. The substrate spontaneously vegetated and when the roof was re-built for waterproofing and later structural reasons in the 1970s and 2000s, respectively. The building caretakers carefully removed the rare and native plants and replaced them on the “new” green roofs. This is an example of a semi-intensive green roof and is a testament to the longevity of green roofs.

Sloped roofs can be greened. The roof shown uses a net and cleat system that functions by balancing the weight of the green roof on one side of gable with the weight on the other side. Thus, the stabilizing cleats must not be anchored to the structure and the waterproofing membrane is not penetrated. Slopes greater than 2:12 require a soil stabilization system. Various manufacturers offer out-of-the-box systems for roofs up to 10:12 pitch, and solutions can be custom engineered for steeper slopes.

The rooftop patio shown here is one of more than a dozen such roofs on the Lenbach Garten, a mixed use development in downtown Munich. Roofs on the Lenbach Garten condos and offices have paver and wood deck patios, swimming pools and jacuzzis, potted shrubs and trees, planted bonsai and other trees, and lawns. Rooftop gardens can be designed to meet any aesthetic goals, given adequate structural support and water management.