I live in Quebec and I read articles from CAA and Rona (Lowes in the rest of Canada) stating that the concrete pillars for building decks posts should be between 4 or 5 feet tall in ground below the frost line to avoid any issue. I am planning to do the number 2 Concrete Pillars Without Footings from this article install a deck foundation
Talking with a Home Depot girl who knows well her job told me that I don't need to be that depth but 2 feet in ground + 6 inches of gravel first using those yellow cardboard quikrete building forms, adding that the weight of the deck is enough to hold the posts there.
Let's say I am planning to isolate and avoid contact of the snow with the posts during the winter. Have you experienced any issue building a deck with 2 feet concrete pilars in ground + 6 inches of gravel below in Quebec instead from the 4 feet long concrete pillar? Any move or stability issues apart from the theory?
EDIT: I mentioned Quebec, but I want to specify I live in Montreal's south shore. This may change the idea that I could live in the North where snow and cold is stronger than in Montreal.