How do I Build and Install a Deck Stairway in a Day or Two?

Mark both sides of the face of the deck where the stairs will attach to the deck. Mark them with an X surrounded in a box that is the entire length of the face board so they are easily visible. Make your stairs at least 36 inches wide.

Measure the height of the steps using a measuring tape. Start at the top of the deck and measure to the ground. Divide this number by seven to determine the number of steps you will need. If seven does not divide evenly into the height of your deck, add one stair to your figure.

Calculate the span of your stairway by multiplying 11 ¼ by the number of stairs you will be using, which you determined in Step 2. The 11 ¼ figure is based on using two boards that are 2-by-6 inches for the treads. This figure will tell you the distance your stairs will be from your deck.

Place a 2-by-4-inch board on the deck two inches outside of the location where you will attach your staircase, and level the 2-by-4. Use a measuring tape to determine where the bottom of your stairs will hit the ground.

Install a footing pad that is at least six inches thick. Dig down six inches into the ground and level it. Pour your concrete footing, ensuring it is level, or use a concrete slab or concrete pavers available from lumber yards and home improvement stores locally.

Cut your stringers to the exact height of the deck from the ground using a circular saw. Measure the distance between the top of the deck and the location you marked in Step 3 that determines where your deck will hit the ground. Install precut stringers to simplify the process, but you may have to raise or lower your concrete footing, so keep this in mind before placing your footing. Cut a stringer for every 16 inches of your deck staircase width.

Attach a piece of 2-by-4 below the 2-by-10 deck face if you need more room to attach the stringers to the deck. Set the stringer in place against the deck and lightly secure it. Drill the holes in the deck joist and stringer to attach two lag screws into each stringer. Attatch the lag screws through the back of the stringer, and secure them to the joist from under the deck. Secure the stringers using 1 ¼ inch lag screws and shields.

Measure the distance between your stringers where they attach to the deck. Level each riser so it is straight from the deck to the ground. Measure between the bottom of the stringers to ensure there is equal distance between the risers at the top and bottom of the stairs. Attach angle brackets to the bottom of the stringers where they lie on the concrete pad. Attach the other side of the bracket to the concrete slab using masonry screws or lags.

Cut your 2-by-6 boards to length using a miter saw or circular saw. Cut the boards so they will hang over about ¾ of an inch on each side of the stringers to prevent problems from board shrinkage. Predrill the holes in your treads, the boards that will become the tops of the stairs, and the stringers to reduce splitting. Secure the boards, two to each riser, using two screws that are three inches long per board. Leave off the final tread on the last riser.

Install the 4-by-4 post at the back end of the bottom stair, next to the stairs. This will be the bottom of your stair railing. Dig a hole for the post, place the post inside, and level the post. Pour mixed concrete in the hole while holding the post level. Install a post on both sides of the stairs if your stairs are not up against a house or building.

Trim the final board around the post. Secure the post to the stringer using two lag screws and shields. Install the final board to the bottom riser.