The structural capacity of the building and roof deck must be able to support the added dead load of the green roof when saturated with water following a rain event. For a simple extensive roof using lightweight media this will be about 7.5 lbs per square foot of roof per inch of media depth. For intensive roofs with heavier media and larger plants this could be much greater. Roofs with a slope greater than 2 in 12 may require a supports to stabilize the roof system. Insulation, if used, must have sufficient compressive strength with withstand the dead and live loads.