Snow (Drifting and Sliding) on residential decks

[Steve1415]

I was recently reading a thread about snow on decks. The thread talked about what loading to use in this situation, but never mentioned the topic of drifting and/or sliding snow on decks. In lower elevation projects where snow isn't a big problem, there wouldn't be any need to worry about such. However, when working with projects for higher elevations, this could make a big difference in the engineering of the deck. Should drifting and sliding snow be taken into account when engineering high elevation decks, or simply just use the flat roof snow load?

 

[msquared48]

For high elevation decks, never discount sliding loads from the roof structure to an exterior deck if the roof layout and slope warrant it. Use the normal snow plus any drifting and/or sliding. Depending on the fall, too, especially wioth wet snow, I would also consider impact.

The only question is how much of the roof snow will slide in any particular situation.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[RVSWA]

Mike's right Steve1415, we have had a number of jobs over the years designing decks that were torn off by sliding snow from an upper roof. They come in with that "Guess we should have had that engineered in the first place" look on their face. The last one ripped the rim joist out along with the deck. The ledger lay on the ground still attached to the rim... that connection was apparently fine.