How to Build Wood Stair Stringers

Decide on the dimensions for your staircase. Build the stringers from 2-inch-by-1- inch lumber or 2-inch-by-12-inch lumber, depending on how tall each rise should be. Select straight boards without warping, knotholes or other damage.

Divide the height of your planned staircase (from the top edge of the top step to the bottom edge of the bottom step) by the height of each planned riser, in inches. This will tell you how many steps you will have and, therefore, how many steps you will need on your stringers. If your total is a fraction, round up to the next whole number.

Multiply the number of steps on your planned staircase by 12. Twelve inches is a standard depth measurement for a stair run. Square this measurement, square the rise measurement and add them together.

Find the square root of the product from step three. This is the necessary length for your stringers. Cut two of your boards to the correct length.

Attach two stair gauges to your framing square. Adjust the gauges so that one marks the run dimension for each step and the other the rise dimension. Align the edge of the square with one edge of the board and mark the riser and the tread of the first step.

Move the square toward the opposite end of the board and line up the edge with the line you just drew. Draw the tread and riser of the next step. Continue until you have outlined all of the steps, then repeat the process on the second board.

Cut out the areas of each board outlined by your marks. Use a circular saw to make the initial cuts, then clean them up with a handsaw. You will have two boards that look like rows of sharp teeth.

Rip the straight edge of both boards so that they are as high as each tread is thick. If you are attaching steps to a wooden structure, attach the boards directly to the blocking with trimhead screws, making sure that they are spaced to accommodate the staircase width. Otherwise, cut a fresh board so that it is as long as the staircase is wide and attach it laterally across the tops of the stringers with trimhead screws.

Cut more boards to fit across each set of treads. Place each across the parallel treads of the stringers, center it, and attach it with trimhead screws. Once the stringers are complete, you can cover the treads with more wood to create wooden steps or prepare the stringers to be filled with concrete.