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Riser Overage or Underage: The riser overage or underage is the difference between the "floor-to-
floor" rise and the total height of all of the risers. Many times the riser height does not divide evenly
into the floor-to-floor rise and a small fraction of an inch is left over. A postitive remainder is an
overage, while a negative remainder is an underage.
Tread Width: The width of each tread is measured from the front of one riser to the front of the next
riser. The width of each tread does NOT include the nosing or overhang of the tread. The nosing or
overhang of a tread is the rounded front of the tread that projects beyond the face of the riser.
Number of Treads: The number of treads is one less than the number of risers.
Tread Overage or Underage: The tread overage or underage is the difference between the run
or horizontal space that a stairway must fit into and the total width of the treads. Similar to the riser
overage/underage, many times the total width of the treads does not divide evenly into the run or
horizontal space for the stairway and a small fraction of an inch is left over. A positive remainder is
an overage, a negative remainder is an underage.
Stringers: Also called carriages, stair horses or stair jacks. Stringers are the diagonal members that
support the treads and risers.
Angle of Incline: The angle of incline of the stairway is determined by rise and run of each stair. The
angle of incline should not be confused with the pitch of the stairway. The pitch of a stairway is the
angle based on the floor-to-floor rise and horizontal run of the stairway. The angle of incline is based
on the "actual" riser height and the "actual" tread width of the stair.
Stairwell Opening: The length of the opening at the top of the stairs. The computation is based on
the headroom height (the desired spacing between the stairs and upper floor ceiling) and thickness of
the upper floor where the opening is located.
STAIRS - GIVEN ONLY FLOOR-TO-FLOOR RISE
Example: You're building a stairway with a total rise of 10 Feet 7 Inches. Your desired riser height is
7-1/2 Inches and desired tread width is 10 Inches. The desired headroom is 6 Feet 8 Inches and floor
thickness 10 Inches*. Find all stair values, then calculate the run.
*Headroom and floor thickness are required to calculate the length of the stairwell opening.
KEY INPUT & DISPLAY
1. Enter known rise:
On/C
On/C
1
0
7
Feet
2. Recall stored desired stair riser height:
7
Rcl
3. Recall stored desired stair tread width:
9
Rcl
4. Recall stored desired floor thickness:
8
Rcl
5. Display stored Headroom (via Preference Setting Mode:)
Conv
Stor
Stor
Stor
Inch
Rise
Stor
Page 26
0
RISE 10
7
Feet
Inch
R-HT
7-1/2
STORED
Inch
T-WD
10
STORED
Inch
FLOR
10
STORED
Inch
HDRM 6
8
Feet
Inch
Cont'd on Page 27
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