How to Calculate the Snow Load on a Commercial Flat Roof

Weighing the Snow

• 1

  Find a relatively flat area of snow on the ground that's at least 1 foot deep and at least 1 foot by 1 foot on the flat surface.

• 2

  Mark out a square that is 1 foot by 1 foot on the surface with your hand, using the tape measure.

• 3

  Dig 1 foot down into the snow, following your square outline, and place the snow you remove into the bucket. Check with the tape measure to make sure you remove enough snow. As you dig, you will be slightly packing the snow beneath, so try to dig as gently as possible and add a little extra snow to your container for good measure.

• 4

  Weigh the container holding the snow. Write this value down as "total weight." Now empty and dry the container and weigh this as well. To get the weight of the snow, subtract this value from the total weight. This is the weight of 1 cubic foot of snow.

Calculating the Load

• 5

  Measure and record the snow depth in five locations on the ground around your commercial building that look to be about the average depth. Take the measurements in feet, converting 2 feet 6 inches to 2.5 feet or 2 feet 9 inches to 2.75 feet, for example. To get a better average, add these depths up and divide by five.

• 6

  Multiply your improved average by the weight of a cubic foot of snow. This will give you the weight of snow on one square foot of an area. Assuming your flat roof is exposed to the snowfall the same way as your building's yard, this value will be the average snow load on your roof.