Because of this there are important safety factors to keep in mind when take on a project of this size. The structural strength of the building we are thinking of putting a green roof on has to be considered owing to the extra weight it will have to carry.
The use of lighter substrates will help as will strengthening the roof supports.
As has been said on our main green roofs page we reiterate - "If there is any doubt to the buildings structural safety with a green roof on it then it's important that we get specialized or professional advice. This would also apply to ensuring the roof is watertight. On both counts it's better to be safe than sorry!"
Do it right and green roofs a grand feature to have in a wildlife garden.