green roofs

huangyhg

green roofs
i am looking for anyone who has experienced or heard of structural complications caused by green roofs.  talking about design of new structures.  unintended consequences.  gaps in codes.  adverse structural effects in structural maintenance, etc.
interesting question. i have not been directly involved with a green roof, but have been observing one for several years on a local restaurant. the plants, including some trees, were of small when the building was completed. over time, they have grown significantly. i have often discussed with  colleagues if the structural design took into account the steadily increasing weight of the biomass. in what is not really a joke, we have wondered when they will have to bring in paul bunyan (lumberjack) to lighten thing up.
...also, for got to mention that the increase height of the trees increases  potential wind loading on the building. we we are in a hurricane prone area.
it has received interest from insurance companies.  there is mention that "water infiltration" has in some cases caused structural degradation in roof framing   
i have not had green roof experience but in urban areas, buildings with landscaped and even waterscaped plazas in front and over basements had been practiced for decades.  
what i recall (it has been almost 20 years since i worked as an owner's rep. with such a plaza) was a plastic drainage tile over a liquid applied membrane with drains, and protected by a concrete topping slab.  the soil (i seem to re