Snow load is the downward force on a building’s roof by the weight of accumulated snow and ice. The roof or the entire structure can fail if the snow load exceeds the weight the building was designed to shoulder. Or if the building was poorly designed or constructed. It doesn’t take a blizzard to cause problems. An imbalance of drifting snow can cause one part of a roof to give, causing a domino effect.
How much snow is too much?
Calculating the roof load on your barn takes more than an educated guess. The University of Wisconsin Cooperative Extension Service says that a ballpark estimate of roof snow load can be made with the following formula:
Calculated Roof Loading (lb/ft2) = Depth (ft) x Density (lb/ft2 /ft depth). The approximate density (lb/ft2 /ft depth) is:
- 5-20 for light snow
- 20-40 for packed snow
- 40-58 for packed snow with ice
- 58 for ice
For example, a roof with 3 feet of light snow has an estimated roof load of 60 pounds per square foot (3 ft depth X 20 lb/ft2/ft depth density = 60 lb/ft2).
You should know the roof weight limits for your barns and outbuildings. If necessary, rebuild or fortify them to withstand worst-case scenario snow loads and meet local building standards.
Some failures can be prevented with careful snow removal.
- Use caution if standing on the roof, making sure to wear a safety harness and use securing ladders.
- Use a snow rake. Avoid chipping or picking away at ice as that may damage the roof.
- Remove snow in narrow strips to keep the load somewhat even.
- Leave a thin layer of snow to protect the roof from damage while snow is being removed.
A few minutes can give you reassurance during a heavy-snow winter. Check with your DFA Insurance agent to:
- Confirm that your property insurance covers roof or building failure due to snow load.
- Make sure the policy pays for actual replacement costs, so you’re not out in the cold if you have to rebuild.
- Verify that valuable equipment stored in a barn or outbuilding is covered under your farm personal property endorsement.