How to Construct Stair Stringers

Stretch the tape measure between the floors' landings to determine the stringers' rise. Divide the rise of a single step by the stringers' rise to determine the number of risers. Seven inches is a standard rise. If your calculation produces a fraction, round the number up to a whole number. Divide the whole number by the stringers' rise to determine the actual height of each riser.

Multiply the total number of risers by the size of a single tread. Ten inches is a standard size. The product of the risers times a single tread equals the stringers' run. Select a piece of stringer lumber at least 2 feet longer than the run. Place a framing square on the lumber's face. Position the framing square's small side toward the board's end and the long side facing the center.

Line up the framing square's small side's measurement marks with the lumber's edge. Find the mark that represents the height of a riser and align it with the edge of the board. Find the mark that represents tread size on the long side of the square. Line up the long side's mark with the board's edge.

Stabilize the square's position, latch square stair stops onto the framing square, butt the stops against the board's edge and screw the stops onto the square. Position the square's short side roughly 1 foot away from the end of the lumber. Press the stops against the lumber's edge. Trace a pencil along the inside edge of the square to create the outline of a step.

Move the square toward the center of the board and position the short side's stop with the corner of the previous outline. Trace the interior edges of the square to create the outline of a second step. Move the square and create layout lines for the remaining steps. Reduce the height of the bottom riser by the thickness of a single tread; this prevents the top tread from protruding above the upper landing.

Lay out lines that run perpendicular from the bottom and top riser marks to the backside of the lumber; these lines indicate the bottom of the staircase and the staircase's top tread.

Rest a portable power saw's base plate on the edge of the stringer. Align the saw's blade with the layout lines. Cut through the layout lines, nearly to the apex where risers and treads meet. Sever the triangular pieces of waste wood from the stringer with a jig saw.