Analysis of information sources in references of the Wikipedia article "Shipping container architecture" in English language version.
The roof load test is 660 lbs over an area of 2' x 1' applied to the weakest part of the roof. The load is usually applied at the center of the containers positioned with the 2' dimension aligned longitudinally. Thus the roof is able to support an imposed load of a minimum of 330 lbs/sq. ft. The design is easily capable of supporting the basic snow loads of 30 lbs per sq. ft. evenly distributed.