How to Make a Deck Stringer

Lay a two-by-four on the surface or floor of the deck, with its outer edge sticking out beyond the edge. Measure the space from the board to the ground below and record it. This measurement gives the total rise of the stairway.

Divide the total stairway rise measurement by the desired stair rise, which is typically 7 inches. Round the result to the nearest whole number to calculate the number of stairs you need. For instance, if the rise measures 64 inches, and the stair rise is 7 inches, the result after dividing the two measurements is 9.14 inches, or nine steps. Divide the total rise measurement, or 64 inches, by 9 to arrive at the rise of each step, which is 7.11 in this case.

Determine the depth of each tread, which is typically 10 inches. You want the stairway to slope to 40 degrees. Position a board up to the top of the deck at 40 degrees and use the point on the ground where it lands as a rough estimate of how far out the stairs will extend. Place another board down from the deck’s edge, and measure from that point to where the deck landing should be. Divide the measurement by the desired number of stairs to determine each stair’s depth.

Mark notches on the 2-by-12-inch stock using a framing square. Position the thin side of the square on the stock so it meets the wood edge at the desired stair rise. For instance, if you want a rise of 7 inches, place the framing square so the edge of the wood lines up with the "7" on the square. Trace along the edge of the square with pencil.

Match up the flat side of the framing square with the depth of each step. For instance, if the tread is 10 inches, the framing square’s flat side should have the 10-inch mark at the wood board’s edge. Trace along the edge of the square with pencil. Repeat this process to form a series of notches on the wood stock that match the desired number of deck stairs.

Subtract 1 1/2 inches from the rise of the bottom step, and 3/4 inches from the rise of the top step to account for the landing and treads. Cut the top and bottom edges of the board at the marks.

Hold the marked wood stock up against the deck to ensure it lies correctly. The base of the board should rest flat on the ground, and the top should fall flush against the frame of the deck. If required, adjust the cuts to ensure a tight fit.

Cut out each notch on the stringer board with a handsaw.