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Stair Stringers (7) Stair stringers form the backbone of a set of stairs. By code, stairs need to be at least 36 wide. Although it's usually possible to get away with just using two stringers, we recommend you add a third one down the middle. This extra stringer will ensure your stairs are exceptionally rigid.
Adjust the height until the height and steps balance out (since you can't have a half or quarter of a step). Take the number of steps and multiply that by 10.5 inches (266.7 mm). That gives you the length of stair stringer necessary. Take that length and project it out from the deck. Now you have the location for the footing of the stair. 3. Lay out the steps on the stringer, using 2 x 12-inch (50 x 304 mm) treated wood, with a framing square. Set the riser for the height determined by your math and the step by 10 inches (250 mm).