What Caused the Uneven Condition of This Wood Deck?
This wood deck exhibited a raised area as shown in the featured photograph and Figure 1.
Examination under the deck disclosed that the elevation of the beam was not level (Figure 2).
Further examination disclosed that the beam was raised at a post (Figure 2). Examination at the base of the post disclosed that the concrete pier had raised (Figure 3). Note the accumulation of water around the post.
The raising of the concrete pier was a result of frost heave, that is, the formation of ice lenses in the soil under the pier. The expansion of the ice (like the increased height of the ice cubes in your freezer) raises the pier and the post.
Sometime a pier and post will drop back down when the ice lenses melt. Sometimes it will drop down more than its original elevation.
Frost heave is one of the reasons that the bottom of footings are required to be set at least 42 inches below grade in Northeast Ohio, that is, except where some other method of frost protection is provided such as, insulation, gravel for drainage, etc.