DIY Modular Green Roof

Hire a structural engineer to inspect your roof. A green roof can add up to 44 pounds of additional weight to your roof when the soil is wet, and you need to be sure that your roof can support that added stress. The engineer will assess the weight-bearing capacity of your home's roof to determine what changes, if any, may be required before installation. In some cases, the engineer may recommend additional waterproofing and/or structural reinforcement for your roof.

Consult a local nursery to determine which plant species is ideal for your roof. Modern green roofing utilizes one or more species of sedum within a lightweight soil medium. Sedum is a drought-resistant plant that can also cope with heavy rain cycles. Some varieties of sedum perform better in cold weather than others, while other types of sedum are more capable of coping with constant heat and sunshine.

Install a drainage layer over your roof. This will consist of a water-tight plastic membrane topped off by a flow-enhancing matrix that will direct excess rainfall to your existing gutters and drainpipes. You will need to use a ladder or scaffolding for this, and for the following steps.

Haul the green roof modules to your roof for distribution over the drainage matrix. While metal trays are commonly used in commercial applications, the least expensive and lightest weight green roof modules utilize high-density polyethylene sacks that are pre-loaded with a lightweight growing medium. The packs will add as little as 11 pounds per square foot to your roof, and they can be arranged on both flat roofs and on roofs that have a low angle of pitch.

Open each pack and plant the sedum plugs. Irrigate the plants using a garden hose, or schedule your planting before an expected rainfall. Eventually, the sedum will spread to form a virtually seamless flow of vegetation across the roof. Supplemental irrigation may be appropriate during the early stage of growth.