ROOFTOP GARDEN TYPES

There are two types of rooftop gardens and depending on the structural design of your roof, one might be preferable to the other. One is the extensive rooftop garden, often inaccessible and the other is the intensive rooftop garden, which is accessible to people.

1. Extensive rooftop gardens:

• Generally lightweight gardens

• Require little or no maintenance

• Vegetation acts like another layer of the roofing material and usually covers the entire roof

• Can be installed on both flat and sloped roofs

• Depending on climate and the amount of rainfall, can grow a variety of hardy grasses, wildflowers, mosses and sedums

• Use drought-tolerant plants that will go into hibernation if exposed to harsh conditions like wind and sun exposure and/or under-wateri

• Since they are not generally walked upon, guard rails, exit requirements and access need not be a concern. If they will be walked on, these aspects need to be considered. SEE THINGS TO CONSIDER - ACCESS AND SAFETY

2. Intensive rooftop gardens:

• Allow for a more diverse plant selection such as perennial flowers, trees and shrubs (all of which can remain in containers over the winter) and the potential to grow food.

• Are subject to building and zoning codes, especially with respect to public safety issues, hence the need for proper exits, guard rails, and lighting.

• Generally installed on flat roofs with the vegetation either covering the entire area or in containers and raised beds.

• A stronger roof structure is required due to the added weight of people accessing the garden as well as higher soil and container weights, decking and trees all adding to the weight impact to the roof.

• More maintenance is required because of the greater variety of plants.

• Other considerations for an intensive rooftop garden include condition of roof, structural and weight capacity, access, cost, irrigation, and drainage.