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Presentation 38:
STAIR SAMPLE CALCULATION
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Sample Stair Calculation
8′-0
″
11 ¼″
• Given:
– Upper Const. = 11 ¼″– Floor to ceiling = 8′-0″– Headroom = 80″– Unit Run = 10 ¾″
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Sample Stair Calculation
8′-0
″
11 ¼″
• Find:
– Total rise– # of risers– Unit rise– Stairwell length
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Total Rise
8′-0
″
11 ¼″
• Total rise =
107
¼″
8′-0″ + 11 ¼″ = 107 ¼″
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Number of Risers
8′-0
″
11 ¼″
• # of risers =
107 ¼″ ÷ 8 = 13.406
14 or 15 risers
107
¼″
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Unit Rise
8′-0
″
11 ¼″
• Unit rise =
107
¼″
107 ¼″ ÷ 14 = 7.66″
7 11/16″
107 ¼″ ÷ 15 = 7.15″
7 1/8″
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Unit Rise
8′-0
″
11 ¼″
• 17 to 18 Rule
107
¼″
Unit Rise 7 1/8″
15 risers
Since unit run is 10.75″
Best unit rise =
10.75 + 7.66 = 18.41 or
10.75 + 7.15 = 17.90
• 7.15 is the better choice since 17.90 is between 17 and 18.
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Stairwell Length
8′-0
″
11 ¼″
• Stairwell length =
107
¼″
139 ¾″
Unit Rise 7 1/8″
15 risers
80″ + 11 ¼″ = 91 ¼″
91.25″ ÷ 7.15 = 12.1667 13 treads in opening
13 x 10.75 = 139.75″
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Conclusion
8′-0
″
11 ¼″
• Find:
107
¼″
139 ¾″
Unit Rise 7 1/8″
7 1/8″
107 ¼″
15
139 ¾″15 risers
– Total rise:– # of risers:– Unit rise:– Stairwell length: