In Germany, buildings with a green roof get a reduction in fire insurance as system can protect the building from fire.  German FLL guidelines state that the design of a green roof should have, at a minimum, a 500mm shingle perimeter to act as a fire break.  There are also guidelines for the percentage of combustible material that is to be incorporated within the green roof substrate.

29 Hundertwasser factory retrofit, Austria, photograph courtesy of Zoe Zimmerman.JPG