What are Snow Loads?
Roof snow load is defined as the weight of snow on the roof surface used in design of the building structure (IBC, 2012).
Snow loads also apply during use of the structure as snow accumulates, one must know when to remove the accumulation.
Snow Load Ratings
When we live in areas where an accumulation of snow can occur, one must consider the winter snow loads.
The weight of snow is dependent upon it's moisture content. Not all snow weighs the same. On average, a weight of 20 pounds is used when defining the weight of 1 cubic foot of snow on a roof. That is, if your shed is rated for 20 pounds of snow load, you will likely reach this loading when you accumulate about 1 foot or 12 inches of snow.
Keep in mind that structure roofs can fail and/or collapse when accumulated snow exceeds the structure's Snow Load Rating.