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