More Green Stormwater Alternatives – Green Roofs

There are a number of things that can be done in addition to building rain gardens. By combining some of these proven techniques you may be able to reduce all the runoff on your property.

Take a look and try them out.

Downspout Disconnection
Rain Barrels
Reduced Pavement or Use of Porous Paving Material
Green Roofs
Plant Native Plants
Plant Trees


Green Roofs

Many people now live in condominiums, apartment buildings and 2 and 3 flats,

Green roof - Rain Garden Network

Green roof at GM Rouge plant Dearborn, MI

most of which have flat roofs, limited space between buildings and unfortunately little or no yard space (front or back). For these situations it may be necessary to capture water before it gets into the gutter through the use of a green roof. Green roofs or vegetated roofs are an innovative stormwater management solution that can clean the air, cool the building and capture rainwater.

There are 2 types of green roofs – extensive and intensive.

Extensive green roofs have a soil depth of 1’’– 5’’. Depending on the soil make-up of the soil mixture the weight of extensive roofs range form 15 to 50 pounds per square foot (wet). The green roofs are vegetated with sedums and sometimes short grasses. Extensive green roofs are often sold in 2’ X 4’ grids so they are easy to pick-up and move around. Costs for “grid” type systems range from $12.00 – $15.00 a square foot.

Intensive green roofs require a minimum of one foot of soil depth to create a roof garden that contains trees , scrubs and perennials. The systems consist of multi-layers of rubber or vinyl moisture and root barriers, organic media and integrated irrigation and drainage systems. Intensive green roofs can weigh for 80 to 150 pounds per square foot (wet) and require intensive maintenance. Costs can range from $50.00 – $100.00 a square foot. Intensive roof systems may also need professional maintenance to keep it growing well and looking good.

Most green roof sales are to commercial customers. Residential customers need to contract with a structural engineer to verify the structural integrity of the roof before a company will sell their product.

Because green roofs are relatively shallow it will be necessary to cover an entire area to absorb all the water from a 1″ to 2″ rainfall. This has a tendency to make the cost of green roofing more expensive then other options.

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