A green roof with grasses and herbs will help control erosion on the land around it, since it absorbs rainwater and prevents run-off, and it will also keep pollution from entering the local water supply. Grass roofs also provide mini-habitats for local birds and insects and they can be a relaxing haven for greenery-starved city dwellers. A sod roof is practically fire proof and will also provide excellent insulation to the building. Not all roofs can be covered in sod, and not all grasses and herbs are well suited for installation on a roof, so do your research before committing to a green sod roof.
Check the local building codes to make sure you are allowed to install a green roof on your house, garage or other building. If the people you talk to are unfamiliar with the construction and benefits of green roofs, you may need to educate them.
Hire a professional roofer or structural engineer to calculate the carrying capacity of your roof. With the accumulated weight of dirt, plants, and snow in the winter, green roofs are very heavy, and your roof's foundation will need to support at least 100 pounds per square foot. Sod roofs also work best on roofs that are flat or have a pitch of less than four inches per foot.
Insure that the existing roof is in good condition, and repair any leaks and reinforce any weak spots before installing your grass roof.
Lay down a waterproof lining, such as heavy duty plastic or liner on your roof. Fold the plastic over itself twice where it overlaps to create a water-tight seam, and attach the plastic to the roof with a staple gun
Build a wood frame around the edge of your roof to hold the soil and sod in place. The frame should be approximately 12 inches tall.
Lay down one to two inches of gravel over the waterproof lining on the roof. This will allow for drainage for your grass and herbs.
Cover the gravel with about 10 inches of high quality topsoil mixed with compost.
Cover the soil with landscaping mesh to hold the soil in place and keep the seeds from washing away before they establish themselves.
Sow grass and herb seeds over the soil mixture, or plant grass or herb plugs, and water well. The grasses and herbs planted on your green roof should have shallow root systems and should be well adapted to the local weather conditions. Most turf grass species work well, and mints, mosses, sedges and sedums can also be a good choice for roofs. Consider growing native plants on your green roof. Native plants are perfect adapted to the local climate, and many have lovely flowers that will beautify your home and will serve as a food source for butterflies, bees, birds and other wildlife. The staff at your local garden center or nursery can help you pick out the best grasses, herbs or other plants for your sod roof.