Stair work is made up of the framing on the sides, known as stringers
(or carriages), and the steps known as treads. Sometimes risers are framed
into the stairs at the back of the treads. The stringers (or carriages)
are 2 to 3 inches thick and 8 or more inches wide. They are cut to form
the step of the stairs.
There are usually three
stringers to a stair if stairs are
more than 36 inches wide—one
at each of the two outer edges
and one at the center. Floor
joists must be properly framed
around the stairwell (or well
hole) to have enough space for
the stair framing and the
Step stringers are fastened at
the top and bottom as shown in
Figures 6-50 and 6-51. These
figures also show the
foundation and give the sizes of
the step treads, as well as
installation methods and post
construction. The types of steps
shown are the most common in
To frame simple, straight, string stairs (Figure 6-52, )—
Step 1. Take a narrow piece of straight stock, called a story pole,
and mark on it the distance from the lower-floor to the upper-floor level.
This is the lower-room height, plus the thickness of the floor joists
and the rough and finished flooring. It is also the total rise of the
stairs. Keep in mind that a flight of stairs forms a right triangle. The
rise is the height of the triangle, the run is the base, and the length
of the stringers is the hypotenuse.
Step 2. Set dividers at 7 inches, the average distance from one step
Step 3. Step off this distance on the story pole.
Step 4. Adjust the divider
span slightly if this distance
will not divide evenly into the
length of the story pole. Step
off this distance again.
Step 5. Continue this
adjusting and stepping off
until the story pole is marked
off evenly. 1he span of the
dividers must be near 7
inches. This represents the
rise of each step.
Step 6. 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.
Step 7. Measure the length of
the stairwell opening for the
length of the run of the stairs.
This length may also be
obtained 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.
RISERS AND TREADS
To determine the width of each tread, divide the number of risers less
one — since there is always one more riser than tread—into
the run of the stairs. This number is used on the steel square in laying
off the run and rise of each tread and riser on the stringer stock. These
figures will be about 7 and 10 inches, respectively, since the ideal run
and rise totals 17 inches. Lay off the run and rise of each step on the
stringer stock equal to the number of risers previously determined by
dividing the story pole into equal spaces. The height, base, and hypotenuse
of the right triangle are now complete.
The following are two rules of thumb that may be used to check the dimensions
of risers and treads:
· Riser height + tread width = between 17 and 19 inches.
· Riser height x tread width = between 70 and 75 inches.
If the sum of the height of the riser and the width of the tread falls
between 17 and 19 inches and the product of the height of the riser and
the width of the tread equals between 70 and 75 inches, the design is