stairs can be
built, the unit
and unit run need to be calculated. See figure 44A. To calculate the
unit rise, measure
the total vertical distance between
finished floor to finished floor. Assume a total rise of 2100
and a desired rise of 180 mm. The desired rise is the height you want
for each step. Divide the total rise by the desired rise to get the
number of unit rises. 2100 mm divided by 180 mm = 11.67 unit
rises. To make all unit rises equal, round off to the nearest whole
number. 11.67 becomes 12. Divide the total rise by 12. 2100 divided by
12 = 175. 175 mm will be the height of each unit rise and
riser. As a
check, 175 mm times 12 = 2100 mm, the total rise. A unit rise
175 is acceptable, according to Table 188.8.131.52., of Page 281 of the
British Columbia Building Code 1998;
because it lies between the upper and lower rise limits of 200 mm and
calculate the unit
the sum of two unit rises from 550
and 700. The sum of one unit run plus two unit rises can not be less
mm nor more than 700 mm. 175 + 175 = 350. 550 - 350 = 200.
350 = 350. 355 mm and 210 mm are the maximum and
unit runs allowed according to Table 184.108.40.206. A run
ranging from 210 mm to 350 mm can be chosen.
44A The Parts Of A Stair
1.Stairs: Calculate The Unit
Unit Run Of Stairs.
Stringer When The Floor Frame Is The Top Step.
Stringer When The Top Step Is Attached To The Floor Frame.
Layout The Rise
& Run Along The Stringer.
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images and text are copyright Ronald Hunter 2005 to 2011