Roof covered with snow

How much snow can your roof take? Well, it depends on how your home was built in terms of its load-bearing ability. If it was built according to most building codes, the roof should be able to take at least 40 pounds per square foot. 

One way to check the snowfall weight is to go to the U.S. Department of Agriculture’s Natural Resources Conservation Service SNOTEL website at https://bit.ly/2yNuqkl.

Select a date and note the latest water content in the column labeled snow water equivalent in inches. If you multiply this measurement by 5.2, it will calculate the weight of snow in pounds per square foot. For example, on Tuesday, April 7, the weight of snow in Fairbanks was 28.6 pounds per square foot.

UAF Professor Emeritus Rich Seifert provided this guidance in the Spring 2011 Alaska Building Science Newsletter.

“It turns out that about 10 inches of (Anchorage) snow is typically equivalent to 1 inch of water content. … A cubic foot of water weighs 62.4 pounds, so every inch of water (equivalent weight of snow) on a square foot of roof weighs about 5.2 pounds. It would take almost 8 inches of water equivalent on a roof to reach the standard roof design load of 40 pounds per square foot … (a) homeowner would be ensuring a safe roof load if he or she shoveled the roof when the load got to 40 pounds per square foot.”

Remember though, that the recorded data on the website may not be close to your home, and the amount of snowfall varies in different areas. The other thing to keep in mind is that the data you get will be snow alone. Thus, if you have a good amount of ice buildup from having a hot roof, you won’t know how much that weighs in addition to the snow. Depending on when your home was built, the slope of the roof, other items protruding from the roof and the material that covers your roof, you may have more or less accumulation than your neighbor even though you both are in the same block or vicinity. 

Finally, if you would like to look at historical changes in local snowfall, you can see what type of trends have occurred in different areas of the state by going to UAF’s Alaska Climate Center at http://climate.gi.alaska.edu/ There is a wealth of information at the center. If you have any other questions pertaining to allowable snow load, feel free to contact Art Nash at UAF Cooperative Extension, (907) 474-6366.

Art Nash is the Extension energy and radon specialist for the University of Alaska Fairbanks Cooperative Extension Service. Contact him at 907-474-6366 or by email at alnashjr@alaska.edu.