In New York state, we built a pergola (a type of garden trellis) using 8x8 pressure-treated posts set 4 feet into the ground. During the first winter, the frost lifted the posts. What should we have done to keep the posts from heaving?
To resist wind uplift, pergola posts should be securely anchored to the ground. For a solid anchor, I prefer to embed pergola posts in concrete, by inserting each post into a Sonotube. If an irregular-shaped hole is used instead, frost will tend to grip the concrete and heave the post. (Another option is to extend the Sonotubes a little above...
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