Let’s take a look Iceland, like all other Scandinavian countries, they always taken pride in trying to live in peace and with harmony with the nature, instead of conquering it. Perfect example for this is the old turf roofs they create. These amazing houses with their grass roofs looks like small greenswards probably seem a little strange for someone. Until the late of 19th century, grass roofs were one the most common type of roofs in Iceland.
Important part here is the thickness of the turf. If the turf is thinner than 15 cm, this could be a problem, this will not make it through a dry summer, also if it is more that 20 cm thick, it will be ample, and the weight probably could collapse over the building. The load of a grass roof is about 60kg / m2, but could reached 90 kg / m2, after heavy rain or snow.