Presentation 36:
STAIR RISE AND RUN
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Rise and Run
Unit Rise
Unit Run
Unit Rise
Unit Rise
Unit Run
Unit Run
Total Rise
• Stairs have a rise and run.
• Similar to rafters, rise is
vertical and run is horizontal.
Total Run
2
Rise and Run
• Unit rise and unit run do not
include the tread nosing.
Nosing
Tread
Unit Rise
Riser
Unit Run
3
Stair Design
• Building stairs involves
several options.
• In this design there
are three treads
and four risers.
Second Floor
First Floor
4
Stair Design
• Another set might
have four treads and
five risers.
• Deciding which to
use depends on
stair usage.
Which is best?
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Rise/Run Rule
•
•
•
•
•
•
A formula is used to keep the stairs at a safe
and comfortable angle.
Rise + Run = between 17″ and 18″
Run + two Rises = between 24 and 25 may
also be used.
The first one will be used for this
demonstration.
7 ½″ rise and 10″ run are numbers that fit the
formula.
7 ½″ + 10″ = 17 ½″
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Starting Information
• Total rise must be
measured.
Second Floor
Total Rise
• Assume for now there
is ample room to land
the stairs on the first
floor.
First Floor
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Number of Risers
• Unit Rise = Total rise ÷ # of Risers
• # of Risers = Total Rise ÷ 8 (Rounded up)
(8 is used as a starting point)
e.g., If the total rise is 30″, then:
# of risers = 30 ÷ 8 = 3.75
Rounding up gives 4 risers.
Note that 5 risers may also work.
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Number of Risers
• Then the unit rise could be either
30″ ÷ 4 = 7 ½″
with 4 risers
or
30″ ÷ 5 = 6″
with 5 risers
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Determining Unit Run
•
Tread width may be found from
the Rise/Run rule.
•
•
17″ – 7 ½″ = between 9 ½″ and 10 ½″
17 – 6 = between 11″ and 12″
11″–12″ 9 ½″–10 ½″
6″
7 ½″
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Example
• What are the possible unit rises and runs for a
stair with a total rise of 102″?
# Risers
Unit Rise
Unit Run
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Example
• 102 ÷ 8 = 12.75  13 risers.
# Risers
Unit Rise
Unit Run
13
12
Example
• Also 14 or possibly 15 risers.
# Risers
Unit Rise
Unit Run
13
14
15
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Example
• 102 ÷ 13 = 7.86  7 7/8″ unit rise.
# Risers
Unit Rise
13
7 7/ 8″
Unit Run
14
15
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Example
• 17 – 7 7/8″ = between 9 1/8″ and 10 1/8″ unit run.
# Risers
Unit Rise
Unit Run
13
7 7/ 8″
9 1/8″ & 10 1/8″
14
15
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Example
• 102 ÷ 14 = 7 5/16″ unit rise.
• 17 – 7 5/16″ = 9 11/16″ and 10 11/16″ unit run.
# Risers
Unit Rise
Unit Run
13
7 7/ 8″
9 1/8″ & 10 1/8″
14
7 5/16″
9 11/16″ & 10 11/16″
15
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Example
• 102 ÷ 15 = 6 13/16″ unit rise.
• 17 – 6 13/16″ = 10 3/16″ and 11 3/16″ unit run.
# Risers
Unit Rise
Unit Run
13
7 7 / 8″
9 1/8″ & 10 1/8″
14
7 5/16″
9 11/16″ & 10 11/16″
15
6 13/16″
10 3/16″ & 11 3/16″
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Design
• Deciding which to use depends on the
intended use and available total run.
– 7 7/ 8″
steep
– 7 5/16″ medium
– 6 13/16″ gentle
• Check local building codes for more
guidance.
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Conclusion
• Stairs have a rise and run.
• Unit rise = total rise ÷ # of risers.
• Unit run may be found using
Rise + Run = between 17″  18″
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