A raised platform deck can be built on a substructure using a concrete block pier and a wood beam substructure by following a basic layout method that can be adapted to any size deck being planned. This type of deck design works well on flat or moderately sloped terrain and can add an attractive and functional exterior area to your home. The procedure described for a deck 12 feet wide by 16 feet long can be adapted to any deck dimensions desired following the same pier and beam layout criteria.
Local and national building codes contain specific structural requirements pertaining to deck construction, beam sizing and pier spacing. It is recommended that you consult your local building department to insure compliance with these code requirements prior to beginning this project.
Establish the outside perimeter dimensions of the planned deck and position a wood stake at the outside corners and at the point where the deck sides meet the exterior wall of the house. Tie a length of nylon string between the stakes to use as a reference line for the finished deck perimeter.
Define a finished deck elevation and mark it on the exterior of the house as a reference or "benchmark" to use during the construction of the deck framing.
Measure a parallel line 2 feet from the house and position a wood stake at both ends of this line, approximately 2 feet outside the deck perimeter line set in Step 1. This will be the first row of pier footings.
Repeat Step 2 to mark pier layout lines at 6 feet and 10 feet from the house and parallel to the house. This establishes a typical 4 foot spacing between support beams, leaving approximately 2 feet of deck cantilever at the face of the deck structure.
Use marking powder to lay out pier locations at each line set in Steps 2 and 3 as follows: one pier 24 inches inside both sides of the deck perimeter line and one each at 4 feet 8 inches of spacing apart. This will position four piers in each row, spaced equally apart and 1 foot from each end.
Use a shovel to dig a pier footing hole at each pier location that is approximately 12 inches by 12 inches by 6 inches deep.
Mix a sufficient amount of premixed concrete in a wheelbarrow to fill each of the pier footing holes dug. Shovel the concrete mixture into each pier footing hole to approximately ground level. Place each pier on the wet concrete and use a torpedo level to level each pier's top block. Ensure that the centre of each levelled top block is centred under the string line set in Steps 2 and 3. Ensure that the top of each pier block is a minimum of 14 to 16 inches below the planned finished deck elevation desired to allow the minimum space required for the deck's support framing.
Allow the pier footing concrete to cure overnight before proceeding to Step 9.
Attach a 4-inch-by-4-inch galvanised post base bracket centre on the top block of each pier with bracket nails provided.
Determine the length of the 4-inch-by-4-inch pier posts needed at each pier by using a transit level. Position the levelled transit and tripod just beyond the deck's perimeter line set in Step 1. Have a helper extend a measuring tape vertically from the planned finish deck elevation marked in Step 2 and record the measurement viewed through the transit at its horizontal crosshair. Next, extend the measuring tape vertically plumb from the top surface of each pier's top block and note the transit reading. Subtract the total of the girder, joist and decking thicknesses and the remaining dimension is the pier post length required. Note the resulting dimension in pencil on the pier block. Repeat this step for each pier.
Cut a length of 4-inch-by-4-inch post for each measurement determined in Step 11. Install the block piece in the post base bracket installed in Step 9.
Place a 3½-inch-by-5½-inch-by-8-foot girder beam, positioned on top of the support posts installed in Step 11, extended to the perimeter line set in Step 1 by cantilevering the beam beyond the first pier. The other end must extend to the centre of the middle pier post. Secure the girder to the pier posts with nails driven diagonally through the side of the girder into the top of the pier post. Repeat this for the remaining girders. The butt-jointed girder ends must be positioned to split on top of a pier post where the joints occur. Check that the girders are level during the installation.
Mark a level line from the top of the installed girders to the exterior wall of the house at both ends and use a chalk line to define the wall ledger line. Cut 3½-inch-by-5½-inch boards to the full continuous width of the deck. This will be the wall ledger for the deck. Attach it horizontally, with the bottom edge aligned with the chalked ledger line. Secure it to the wall framing with two 16d galvanised box nails at 16-inch spacing into wood framing or with ½-inch-by-4-inch bolts and wall anchors into a cement foundation wall.
Mark a 24-inch joist layout on the top of the wall ledger installed in Step 13, beginning the first mark at 23¼ inches and 24 inches apart for all of the remaining layout marks over the full length of the ledger board. Square the layout lines down the face of the ledger board.
Match the layout marked in Step 14 onto the top surface of the outside girder line. Use a chalk line between the wall ledger layout and the outside girder to mark the joist layout on the girders between.
Cut and install a 3½-inch-by-5½-inch-by-12-foot deck joist on edge at each of the layout lines and one at the end of the girders on both sides of the deck. Install a joist hanger at the ledger end of each deck joist to secure the joist to the ledger board.
Add a row of bridge blocking between the deck joists at each girder line.
Use a piece of nylon string stretched from the ends of the two outside joists to check that the deck joist ends are aligned straight. Attach a 3½-inch-by-5½-inch board to the outside ends of the deck joists, making certain to maintain the layout to keep the joists straight. Attach the board with two 16d galvanised box nails at each joist end. This is the rim joist for the deck.
Install the 3½-inch-by-5½-inch decking boards, beginning at the front edge of the deck. Cut the boards to the full width of the deck plus 1 inch. Extend the edge of the first line of decking boards ½ inch over the face of the rim joist and ½ inch over at each end. Secure the board in place with two 2½-inch galvanised flathead deck screws at each joist.
Repeat Step 19 for the remaining decking boards to complete the deck structure. Maintain a consistent gap of ¼ inch between the decking boards.
The pier footing holes can be dug deeper in Step 6 to maintain the required distance needed for the deck framing. It is recommended that the top of the pier should be no less than 4 inches above the finished grade of the surrounding ground. It is advisable to do some simple rough grading of the area beneath the new deck to promote adequate drainage. Making certain the first decking board is installed straight and secured ensures a consistent straight line for the remaining decking boards. Use a carpenter's pencil or screwdriver shaft to maintain the consistent gap between the decking boards during installation.