How to Float a Deck on a Slope

Outline where the deck will be using the stakes and the string. Place stakes everywhere there will be a vertical post. The number and spacing of posts depends on the height of the deck and the predicted traffic and weight loads.

Dig a 12-inch hole at the site of each stake, being sure to center the hole where the stake was. Place a tube form over the hole. Mix concrete in the wheelbarrow with the shovel, following the instructions on the package. Pour concrete into the tube forms. Allow the concrete time to dry, per the instructions on the package.

Drill holes in the concrete blocks, using a bit that is slightly smaller than your masonry screws, in the places that correspond with the predrilled holes in the post anchors. Attach the post anchors to the concrete blocks using the masonry screws.

Cut 6-by-6-inch posts to the length that ensures the deck will be level. On a slope, this means that the posts will be different lengths to compensate for the sloping ground. Use the string and the level to ensure that the posts are a height that makes the center of the string between them level. At first intentionally make the posts slightly too tall, then use the circular saw to trim the posts to precisely the right height.

Cut 2-by-10-inch beams to the length and width of the deck. Secure them in a rectangular frame shape using the metal mounting brackets and nails. Add joists across the frame, one per 16 inches, using metal mounting brackets at either end.

Float the frame into position at the top of the posts. You will need many people to do this, as the frame is quite heavy. Drill holes through the joists and the posts and bolt them into place by putting a bolt through the hole and a washer and nut around the threaded end.

Lay the first few decking boards across the top of the frame using the stepladder. Make sure the decking boards fit snugly together. Nail them into place by putting a wood nail through the board into the joists. Once the first few boards are in place, you can stand on this platform and build your way out. Be careful not to fall off.

Using string and chalk, snap a line along the edges of the deck where the decking boards hang off the joists. Cut off the tips of the decking boards to create a flush, clean, straight edge using the circular saw.

Finish the deck with a sealant meant to prevent water damage.