Installing Deck Footings

I’m replacing my old deck with a new one, complete with new footings and posts.

Q. I’m replacing my old deck with a new one, complete with new footings and posts. One corner of my old deck would move up several inches in the spring, then move back down as the weather warmed, but it never quite settled to the previous level. What causes this weird seasonal levitation, and can I prevent it when I build my new deck?

A. Your deck has a bad case of frost heave. In the winter, the ground freezes from the top of the soil downward. The depth of frost penetration depends on the soil type, the severity of the winter, the amount of water in the soil and the depth of an insulating blanket of snow.