Concrete pier blocks form a floating foundation for decks. A floating foundation rests on top of the ground rather than extending below grade. Below-grade foundations provide more stability than floating foundations and are less prone to shifting due to freeze and thaw cycles each year. However, the piers are simple to install and provide adequate stability for wood decks.
Mark the locations for the pier blocks by placing wood stakes at the corners of the planned deck. Connect the stakes with carpenter’s string to form the perimeter of the deck. Mark the locations of the piers, every 48 inches, along the strings with stakes or spray paint markers on the ground.
Excavate the sod from each pier location. The plant material in the sod will decay under the pier, which can cause settling of the deck. Fill the excavation with gravel and pack tight with a hand tamper.
Place the concrete piers on the gravel pads. Place a straight board between the piers and check the level with a 4-foot carpenter’s level. Roughly level the piers to within an inch or two of level by removing or adding gravel as needed below the piers.
Set a 1-foot segment of 4-by-4-inch treated post in the recess at the top of each pier. The concrete is shaped to accept this type of lumber. These posts will serve as the supports connecting the deck to the concrete pier foundation. Attach the frame of the deck to the post at the appropriate position to produce a level deck.