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Competency: 305.00 Design and Draw Stair Systems

Competency: 305.00 Design and Draw Stair Systems. Objective: 305.03 Explain the calculations for rise, run, total rise, total run, and floor cutout. Building Considerations. Minimum headroom = 6’-8” Riser height = 7” to 7-5/8” Riser material thickness = ¾” Tread depth = 10” to 11-1/2”

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Competency: 305.00 Design and Draw Stair Systems

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  1. Competency: 305.00Design and Draw Stair Systems Objective: 305.03 Explain the calculations for rise, run, total rise, total run, and floor cutout.

  2. Building Considerations • Minimum headroom = 6’-8” • Riser height = 7” to 7-5/8” • Riser material thickness = ¾” • Tread depth = 10” to 11-1/2” • Tread material thickness = 1-1/4” • Tread width = 36” clear above/below handrail • Handrail height = 30” to 38”

  3. Building Considerations • Guardrail heights • Required if landing is 30” above floor or grade • Minimum height = 36” • Vertical members spacing maximum = 4” • Do not allow passage of 6” diameter sphere

  4. Building Considerations • Require handrail for 4 or more risers • Minimum 1-1/2” between handrail and wall • Handgrip does not exceed 2-5/8” in cross-section • Local codes for winders, spiral stairs, illumination, etc • Nosing projects 1-1/8” to 1-1/2”

  5. General Design Rules • Slope (rise-to-run) ratio between 300 and 350 • Sum or two risers & one tread equals approximately 25” • Riser height multiplied by tread width equals approximately 75” • Sum of one riser & one tread equals 17” to 18”

  6. Total rise Distance: finished lower floor to finished Thickness of ceiling material Width of floor joist Thickness of subfloor Thickness of finished floor Example:8’-0” (gypsum board or drywall)1/2” (2”x 8” joist)7-1/4” (1/2” plywood sheathing)1/2” (floor & underlayment)1” Total Rise = 8’-10 ¼” Stair Calculation

  7. Number of risers Convert TOTAL RISE to inches Divide TOTAL RISE by 7 Example: TOTAL RISE = 106.25” 106.25 / 7 = 15.17 Number of risers = 15 or 16 Stair Calculation

  8. Height of riser TOTAL RISE inches Divide by number of risers Each riser must be equal in height Example: 106.25” / 15 TOTAL RISE = 7.08” Stair Calculation

  9. Stair Calculation • Ensure accuracy of riser and tread dimensions • One less tread than risers

  10. Total Run Tread width multiplied by number of treads Example Tread width = 10” Number of treads = 14 TOTAL RUN = 140” Stair Calculation

  11. Stair Calculation • Floor cutout size (upper level) • Lay out scaled drawing and calculated rise/run information • Draw a line, along stair nosing, from bottom tread to top tread • Measure vertical line representing headroom • Draw a parallel line from bottom tread to top tread • Measure resulting stairwell rough opening

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