Stair framing is figured by run and rise and is not computed by base feet, as in nearly all construction. The run of the step is the horizontal or tread line and the rise is the perpendicular or rise line. We must determine the number of treads and rises for the span of the stair. Cut a pole the length from the top of the finish floor below to the top of the finish floor above. With a compass space the desired number of rises in the stair. There is one less run than rise in laying out the stair. Plumb from the header above to the floor below.

Fig 51

Allow 1 1/4" for finish, and measure back the length of the run of one tread as many times as there are number of runs in the stair. (Fig. 51.)

Where there is a certain amount of space for the stair, divide the same with the compass for the number of runs required, one less than the number of risers.

The tread is l 1/4" wider than the run for nosing. The finish rise is the same width of the rise of the stringer. (Fig. 52.) Example: The height from finish floor below the top of finish floor above is 9' 4", or 112". Keep as close to 7" rise as possible, where there is room for the run. There are 16 rises, 112 divided by 16=7" rise.

F1g. 52

Where there is space, make the run 10" for a 11 1/4" tread. To locate the header of opening, find the number of runs and rises in the stair as described, and locate the first rise. The plumb line between the rear header and stair tread should be 6' 8" to 7'. The ceiling is 8' 6", the third riser is 21" high, the distance between the third rise and ceiling is 6' 9". Plumb up from the third rise for the header of the opening. (See fig. 51.) Lay the square at 10" run and 7" rise on the stringer to be cut out, as many times as there are runs and rises in the stair. Cut off the bottom of the first rise the thickness of the finished tread. Nail this stair horse on the finish stringer 3" from the top edge to the point of rise and run to support the rise and tread. Cut out of finish stringer at the top that rests on the floor, the thickness of the tread and cut the top and bottom of the finish stringer to meet the base with mitred joint. (Fig. 51.) Take the width of opening and deduct the thickness of stringers for the length of the tread, straighten and square a tread for a pattern to mark all other treads and rises, using a knife point to do all marking.

Nail the risers and treads in firmly. If the one side is exposed, allow for an outside finish string. There are different methods to build stairs. The treads and risers may be housed in the finished stringer and wedged and glued. All stairs are figured on the method described, whether two or more risers and runs. Any one wishing to make a specialty of stairs work can obtain books especially for stairs.