In urban areas like the Washington region, roofs with vegetation may offer outdoor green space and garden options to people who otherwise may not have access to them, said landscape designer Julie Udani, principal of Arlington-based Greener Gardens LLC.
"The most important thing is to make sure that your roof is structurally strong enough to support this," Ms. Udani said. "Most of the time it is, and it depends on the system you use. If the soil is only about 31/2 inches thick, for example, it's not crazy heavy for a regular roof. But I would have an engineer come and see how much load your roof would be able to carry."