Reader Edgar wrote:
“If you are going to be walking around on your roof planting petunias, make sure your homeowner’s insurance is adequate (not to mention your personal health insurance). What does Al Gore have planted on his roof?”
To Edgar: before you start planting anything on your roof, you want to do two things.
First, have a structural engineer examine your roof to determine it is safe to handle the weight load. We removed 10,000 pounds of old roof and added 14,000 pounds (net gain: 4,000 pounds) and that is assuming that the soil is fully saturated and the plants are fully mature. Our structure is more than enough to handle the load.
Second, you want a new roof, one that is made of PVC (or equivalent) to insure that you don’t spring a leak. I wound never advocate putting a vegetated roof on an old roof. My confidence in our roof not leaking is strong. I have no doubt it will be fine for many, many years.
I don’t know what Al Gore has planted on his roof, but I understand Bill Clinton has yellow roses on his library roof.
— JIM MUMFORD