Snow Drift on at Grade Deck with Canopy

As nuts as it sounds, this has the potential to really kill me on the foundation design for the canopy/deck posts. They're screw piles that max out in the 20-30 kip range. I may need multiple piles per post which is raising some eyebrows.

Around here we get hurricanes and nor'easters that throw wind at us from 360 degrees depending on the track of the storms center of rotation. I've heard tell, however, that there are places where storm winds come from one direction and only deviate a 10-20 degrees from that track. Could this be one of those places? If so, maybe you could rationalize only using leeward if it's always coming from the other way? It could be risky, and you'd have to have dependable climate and weather data, but it could be better than being the guy with 34 screw piles to support a deck...

Sounds like a great spot for skiing.

BA

phamENG said:

..and you'd have to have dependable climate and weather data

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Yeah, I've seen wind tunnel studies on big buildings echo that. This is just a fancy house in some of the best ski country in North America. A wind study would cost more than the damn piles.

Are you designing for Banff? Also, sorry in advance as I have nothing great for you here.

Answers to your questions
A) c_t at 1.1 as I see it more like a structure kept just above freezing. See this thesis (page 42) about temperature of snow in a mountain climate at 2cm above grade being just around 0 Celsius.
B) I see no justification for saying that the snow will not fill the deck area. Having lived in Parry Sound and made many a ice rink / hut structures on the ice I can easily see that happening. This abstract suggests that such phenomenon has been observed at grade-level base camps in polar regions whereby they become completely inundated.

Ideas

A) Consider perimeter collector fences along deck edge perhaps with a lattice top. However, given the depth of snow probably set an additional one even further back would be ideal.
B) Transplanted mature hedges to perform the same function

Those and other ideas from the NRC.

Secondary Ideas

A) At this height of snow I do not think it would be crazy to consider arching at the deck perimeter. Think of snow forts and how well those stand up when we used to tunnel through them! Granted they were densely packed, as are igloos, but I have to imagine at 10ft in height some packing occurring within the snow pile. This might reduce loads considerably depending on what you are willing to assume.
B) If you at all buy A) then you might buy that there is some friction at the snow / wall interface. You might imagine some sort of beam made of...snow extending out some distance from the face of the wall which will be supported by this friction and not your piles. Think of a Snow Cornice.
C) Such an unimportant structure you may want to consider Is = 0.8
D) Can you get your hands on a set of drawings for anything local already built?

Enable said:

Are you designing for Banff? Also, sorry in advance as I have nothing great for you here.

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No, this one's a ski resort much further down the rocky mountain chain. You didn't have anything on this that was immediately actionable but interesting thoughts none the less, thank you.

Enable said:

Can you get your hands on a set of drawings for anything local already built?

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No easily. What I do know about a neighbor's property is that it's in litigation because the decks settled 4" relative to the main building. I don't know that's snow drift related though. This site has collapsible soils which are some fo the worst I've had the misfortune to encounter.