- 1). Communicate with the local building department in your area to determine the requirements, codes or restrictions associated with building a vegetated roof. Be aware that you may need to purchase a permit before beginning this project. Before placing any grass on the roof, make sure it provides a pitch of between 5 and 20 degrees, in order to allow for proper water drainage.
- 2). Measure your roof, and determine how much vegetation you will need. Buy the proper amount of vegetation, along with an appropriate underlayment system for the vegetation roof. The underlayment system will typically be composed of several layers of insulation, a type of moisture barrier, drainage protection and a filter. Install the system, being careful to follow directions closely.
- 3). Place a layer of soil or another type of growing medium on top of the newly installed underlayment system. Lightly mist the growing medium until moist, and carefully sprinkle the grass seed over the top of the growing medium.
- 4). Water the seeds. Keep them moist during germination until they are established.
- 5). Continue watering the grass during times of drought once it has been established. Since the grass on your roof won't have the same depth for its root system that it would if it were in the ground, it will need water at least once a week--so if it doesn't rain that much in your location, you will have to water it.
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