We have been getting a lot of calls recently about people concerned if it’s time to shovel their roofs.  For many roofs, it may be. In Tahoe, a warehouse collapsed, a 3-story apartment building was nearly completely buried in a 25-foot avalanche, and a porch collapse resulted in a fatality. In Lava Hot Springs Idaho, the Moon Bar and Grill collapsed recently, trapping two people inside. Don’t wait until heavy snow loads overtake your building or home. If you are considering having your roof snow removed, there is a reasonable method to estimate if it is time.

Roofs are designed for anticipated snow load. That can be roughly equated to a design snow depth. A good way to estimate the design depth of roof snow (the depth at which it should be shovelled) is the following:

1. Look up your design ground snow load (Pg) at your Authority Having Jurisdiction: Placer County | Truckee | Nevada County
2. Using that snow load, you can get an estimate of the snow density (D) by clicking here, or just use D= 25 pounds per cubic feet (PCF).
3. Calculate your flat roof snow load (Pf) as 70% of Pg.
4. The design depth of your roof snow load is approximately: Pf / D

It’s not super-accurate, but it gives you a number that you can use to help consider when to shovel.
This all assumes that your house was built to code after 1973, when those snow loads were developed for these jurisdictions.

Another good indicator of when to shovel is when distress is apparent in the house. If nails are popping, gypsum board is cracking, and doors are sticking, your framing has likely reached its deflection limit. Reaching that limit is typically not a safety issue, but a safety issue or structural damage can be imminent.

Remember, Linchpin offers this advice without seeing your structure or providing engineering services. Take the advice with that understanding. We take no responsibility for your property and recommend you hire an engineer if you need one.