e. Continue this adjusting and stepping off until the story pole is marked off evenly. The span
of the dividers must be near 7 inches. This represents the rise of each step.
f. Count the number of spaces stepped off evenly by the dividers on the story pole. This will
be the total number of risers on the stairs.
g. Measure the length of the stairwell opening for the length of the run of the stairs. Obtain
this length from the plans. The stairwell-opening length forms the base of a right triangle. The height
and base of the triangle have now been obtained.
2-20. Stairway Dimensions. Standard procedures can be used to determine the height of the rise, the
length of the stairway, and the width of tread.
a. Rise Height. In order to determine the height of the risers, use a set of dividers and set
them at 7 inches. Now step off the distance on the story pole from one end of the pole to the mark
you made on the other end. If the distance will not divide into the length of the story pole evenly,
adjust the divider spans slightly and again step off this distance on the story pole. Continue adjusting
and stepping off until the story pole is marked off evenly. Now count the number of spaces stepped off.
This will be the total number of risers in the stairs.
b. Stairway Length. Measure the length of the stairwell for the length of the run of stairs. The
length may also be obtained from the details on the pane.
c. Tread Width. To determine the width of each tread, divide the number risers, less one
(remember there is one more riser than thread), into the run stairs. The numbers obtained are to be
used on the steel square in laying off the run and rise of each tread and riser on the stringer (see Figure
2-39).
Figure 2-39. Laying off run and rise
2-29
EN5156
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