How to Build a Deck on the Side of a Hill

Install the ledger on the side of your home. The ledger consists of 2-by-8 boards fastened directly to your house. Build the deck out from the ledger and anchor it to that length of wood. Usually, the ledger screws directly into the side of your house. Place a level on top of the ledger to ensure it is straight.

Measure out the distance from the ledger to the point where you intend to have the edge of your deck. Mark the positions for your deck footings by driving stakes into the ground. Measure 3 feet back toward your deck and drive two stakes into the ground. The two stakes mark the positions for temporary support posts.

Build the support posts. Lay two 1-foot long 2-by-4s on the ground. Level them by scooping dirt beneath them with the trowel. Anchor the two bases with stakes. Nail two pairs of 8-foot long 2-by-4s together to form two temporary posts. Toenail a post into each base. Create a diagonal brace for each post with another 2-by-four, nailing the top of the brace into the post and anchoring its bottom to the dirt by nailing it to a stake driven into the soil. Ensure the temporary posts are straight by checking them with the level.

Hold a long 2-by-4 up against the ledger, directing it out over one of the temporary posts. The bottom of the 2-by-4 should be flush against the bottom of the ledger. Mark each temporary post where the bottom of the 2-by-4 touches them. Cut off the top of the posts at that mark using the reciprocating saw. Nail together two 2-by-fours that are 2 feet longer than the intended width of your deck to make a temporary support beam. Center the temporary beam on top of the temporary posts and toenail it into place.

Construct the outer frame of your deck by nailing together the 2-by-8s you’ve chosen for the outer frame. Screw the galvanized metal joist hangers into the 2-by-8 that faces the ledger on your house. Place the first joist hanger in the center of the board, securing it with 10d joist hanger nails. Space the other joist hangers 16 inches off the first one, moving out toward the edges of the frame. Install joist hangers on the ledger in the same way, installing one in the center and then installing the others at 16 inch intervals. Lift up the frame and move it into place against the ledger. Use the support beam placed on the temporary posts to support the frame. Fasten the frame to the ledger by screwing metal angle brackets to the frame and the ledger.

Hang the plumb line from one of the out corners of the deck frame. It should hang down over the stake you pounded into ground. If not, move the stake so it is centered beneath the plumb line. Hang the plumb line from the other outer corner and check the stake there, as well as for any other posts you plan to build to support the outer edge of the frame.

Dig holes for the support beam footings with a posthole digger. Dig straight down at the exact spots you marked with the stakes, excavating soil to a depth of 30 inches. Pour loose gravel into the finished hole until it fills the bottom 2 inches of the hole. Cut down the concrete tube forms to 32 inches. Place each one into a hole and fill in the sides of the hole with dirt so the tube is held firmly upright. Create the cement mix according to the manufacturer’s instructions. Shovel it into the tube forms until they are filled. Level off the top using the wooden smoother and check to be sure the top is even using the level. Insert a J-bolt into the very center of each footing. Wiggle the J-bolts down into the cement until only 1 inch of each is exposed above the mix. Let the footings cure overnight. In the morning, cut away the visible cement tube forms with the utility knife.

Center a metal post anchor over each J-bolt on the footings. The post anchor should be square beneath the deck frame above it; hold a 6-by-6 beside it, raised up to the frame to check. Hand-thread a nut over the J-bolt and tighten it into place with a ratchet wrench. Measure the distance between the footing and the deck frame; cut the 6-by-6s into posts of that length using the circular saw. Nail the saddle hardware into place on the top of the post using 10d galvanized joist hanger nails. Place one post into the post anchor on one footing, standing it up straight so the deck frame board slides into the saddle hardware to be cradled and supported. Nail the post into place in the post anchor with joist hanger nails, then nail the deck frame beam into the saddle hardware with the same type of nails. Install the other posts in the same way.

Measure the distance between the ledger and the deck frame board parallel to it. Cut 2-by-8s to that length with the circular saw. Slide each 2-by-8 into a joist hanger, then nail them into place with joist hanger nails.

Measure the length of the deck perpendicular to the joists. Cut the 2-by-4s to that length. Lay them out on the deck and nail them into the support joists with corrosion resistant decking nails. Space the boards one-quarter of inch apart to give them room to expand.

Take down the temporary support posts and beam.