- Measure the rise and run of the steps. Rise is the difference in the heights of the two floor surfaces the steps will connect. The run is the horizontal distance from the front of the bottom step to the edge of the upper level's floor surface.
- Calculate the number of steps. Steps commonly have an individual rise of about 7 inches per step. Divide the rise of the stairway by 7 to determine the number of steps. Since fractional steps are not feasible, you will round to the nearest whole number. For example, a rise of 55 inches equals 7.86 steps. Round this to eight steps. Divide the rise by the planned number of steps -- in this case, 55 divided by 8 equals a rise of 6 7/8 inches for each step.
- Measure the length of the riser, using a tape measure, from the top of the upper-level floor to the point on the lower level where the steps will end. Cut a 2-by-12-inch board to this length to be a stair stringer. Standard stairs need at least two stringers; wider stairs require three or four.
- Mark a notch in the stringer that has a drop equal to the rise you calculated, and a tread equal to the width of the intended stair tread. Two 2-by-6-inch boards, measuring a combined 10 inches across, are commonly used as the tread.
- Continue marking out the notches with the start of the rise at the point where the tread mark reaches the edge of the board. When complete, the marked notches should resemble a sawtooth pattern on the stringer. Use the first stringer as a pattern for the rest of the stringers.
Things You Will Need
- Tape measure
- 2-by-12-inch lumber
- Carpenter's square
- Mark out the stringer and trial place it before making the cuts. Confirm the planned cuts result in evenly spaced stairs with the treads parallel to the floors.