It's the middle of summer, and probably the last thing on your mind is freezing weather. But as you build those decks and porches, sinking pressuretreated posts or sonotubes into the ground, you'd better think about next winter — and what frost might do. Frost heaving is extremely difficult to control and also generally misunderstood. Those of us in the northern tier of the U.S. know the demonstrations of frost all too well: The earth bulges and carries buildings and roads with it. The bulges are uneven, lifting one or two posts on the porch, a single corner of a building, a patch of roadway, or a small section of an exposed slab. The results of frost