I (the homeowner) have owned a roofing company for 15 years and after looking at 20,000 roofs I started to see that roofs that grew moss on them stopped aging. I think all green roofs should have at least a 3/12 pitch to allow water to run off. When you put a green roof on a flat roof you first have to pay to install a good roof then gravel to allow for drainage that will require engineering. My roof has no roofing under it; it is 10 lbs. per sq. ft., so no engineering. I do have felt paper and I recycled a cedar shake that was on its way to the landfill. I put it on the roof backwards to allow drainage and to hold 1 inch of sod in place.

This system can go on any home – mine is 110 years old with a 12/12 pitch. Life expectancy could be 900 years – I believe this because they have done it in Norway and if the radiation from the sun cannot see your felt paper, it will last forever. The radiation is what breaks down all roofing.

This system is very simple. You can simply lay sod on your roof and you’re done. You should install a 2×4 border around the edge of the roof. If you don’t think the water will drain install cedar chips, branches, or even old lap siding on the roof. I live in the NW of the USA so I used cedar shingles which were free for the taking. Simply lay the cedar on the roof backwards, find a used fish net, put it over the cedar and anchor it down. Lay the sod on the cedar and put a fish net over that; the grass will grow through on both sides this will prevent the wind from blowing it off. The cedar has pockets of oil in it and should last 600 years, not exposed to the sun’s radiation.

This is the only system that I know that has a negative carbon footprint. If you want to push the envelope on the carbon footprint, tear-off your old roof install Polyply (polyester paper like Tyvec) on the roof, then install a 2×2 with anchors, not penetrating the Polyply (use an angle bracket under the overlap of the paper), then install another layer of sheeting to create a 2″ air gap for venting – roots will not grow through a 2″ air gap. Last, install a sprinkler system and your system will be bullet proof. Without the sprinkler system your system will brown, which is OK when it rains – mother nature will then grow you another roof.