We just bought a flat roof house and while we love it we have no idea how much snow it can hold without caving in around us. Is there a way to calculate the snow load and how much it will bear on a flat roof?
Answered: 2019-10-23 06:29:13
You want to make sure if you have a flat roof that you first figure out how deep the snow is piled up there. The easiest way is to push a yardstick into the snow on the roof, where you select an area that looks pretty much like the rest of the flat roof in terms of snow depth. Then you express the result in feet rather than inches so if is 24 inches you use 2 feet. Then you take snow from the ground and you put it into a container that 1 feet high and 1 feet wide. Weigh the container before and after you fill it with snow. The weight will differ depending on whether the snow is dry or packed. A cubic foot of dry snow weighs about 6 to 8 pounds, while 1 cubic foot of packed snow can weight 20 pounds. To figure out how much load your roof can bear - take the depth of your snow thats in feet and multiply by the weight of the cubic foot. If yur snow weighs 10 pounds per cubic foot and there is 1.5 feet on your roof, each square foot of the roof is getting 15 pounds of pressure. description
You can find the equation for converting ground snow load, pg, to roof snow load by using the pf. This is the equation that includes factors that take into account exposure and building heat loss. It also includes the importance factor seen in other load types that helps converts data to different mean recurrence intervals according to the type, height, width, etc. of the structure. description
Wet and saturated snow weighs about 20 lbs./cubic foot. Use this as your basic formula but always double check with your weather station if you have wet or fluffy snow. Then use Snow with a 1.25 = P where S is the number of snow inches on your roof and P is the pound per square foot of the snow.
Two feet of snow can equal up to 19 tons of weight on your roof. description
You take your roof length by feet and inches and you take your roof width by feet and inches. then you take your roof pitch (x:12) and then figure out what the angle is your roof makes the horizontal for the degree calculation. They you take the snow cover thickness and determine if its wet or dry snow with the total snow weight by lb. You'll be able to determine the permissable load on the roof by multiplying 3.59 by the maximum level of snow thickness to get the load bearing measurement. description
For load bearing purposes the ground snow loads lower than 20 pounds per square foot, the roof snow load is equal to 70 percent of the product. This is due to the snows exposure, thermal and importance factors and the ground snow load. Ground snow loads greater than 20 pounds per square foot, but the roof load is equal to 70 percent of the product of the exposure, thermal and importance factors, the ground snow load plus 20 (pounds). description
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