Pier blocks are pyramid-shaped concrete blocks with a piece of wood or a metal post bracket set into the top. They are used to support 4-by-4 posts in post and pier construction, a method often used when making decks and patio foundations. This method is also used sometimes in home and cabin construction, but it is not very stable and is not usually recommended for this purpose, especially in earthquake-prone regions.
Outline the perimeter of the foundation and set a pier block at each corner and at 8-foot intervals around the perimeter. If you plan to run beams through the middle of the foundation rather than hanging joists from joist hangers, set blocks at 8-foot intervals inside the perimeter.
Dig a hole for each pier block so that 1/2 to 2/3 of the block is underground. Tamp the bottom of the hole with a tamper and use a torpedo level to be sure the top of the pier block is level. Back-fill the hole with concrete mix and let it set.
Attach metal post brackets to the top of each pier block by nailing them in place with 1-1/4-inch nails. Some pier blocks have these preset into the concrete.
Set a 4-by-4 post into each bracket and nail the bottom to the bracket with 1-1/4-inch nails.
Determine the height of the floor, taking into account the width of the beams and the thickness of the flooring, and use a line level to level the tops of the posts relative to each other at the correct height. Cut the posts with a hand saw or circular saw. Attach a 4-b-4 X 4-by-6 beam holder to the top of each post, orienting the holder in the beam direction and nail it in place with 1-1/4-inch nails.
Set beams into the holders and, plumbing the posts with a level as you go, nail them in place. If it is necessary to join beams, do it at the midpoint of a post and nail both beams to the holder.
Nail 2-by-8 joist hangers to the insides of a pair of facing beams at 16 to 24-inch intervals if you have set no beams in the middle of the foundation. Then set the joists in the hangers and nail them in place. Use 1-/1/4-inch or joist hanger nails for both connections.
Toe-nail the joists to the tops of the beams if you have set beams in the middle of the foundation.
Using screws instead of nails to attach the wood to the brackets is sometimes easier to do. This method has the advantage of being undone more easily if you make a mistake or need to change something. Using pressure-treated wood as your foundation material will make the foundation last much longer.
If your deck, patio or floor is high, cross-brace the posts with 2-by-4 lumber for strength and stability. Metal strapping is available for this purpose and is widely used in earthquake zones.