Competency 305 00 Design and Draw Stair Systems

Building Considerations n Minimum headroom = 6’-8” n Riser height = 7” to 7

Building Considerations n Guardrail heights n Required if landing is 30” above floor or

Building Considerations n Require handrail for 4 or more risers n Minimum 1 -1/2”

General Design Rules n Slope (rise-to-run) ratio between 300 and 350 n Sum or

Stair Calculation n Total rise n Distance: finished lower floor to finished n Thickness

Stair Calculation n Number of risers n Convert TOTAL RISE to inches n Divide

Stair Calculation n Height of riser n n Example: TOTAL RISE inches Divide by

Stair Calculation n Ensure accuracy of riser and tread dimensions n One less tread

Stair Calculation n Total Run n Tread width multiplied by number of treads n

Stair Calculation n Floor cutout size (upper level) n Lay out scaled drawing and

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

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

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

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

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

Stair Calculation n Number of risers n Convert TOTAL RISE to inches n Divide TOTAL RISE by 7 n Example: n TOTAL RISE = 106. 25” n 106. 25 / 7 = 15. 17 n Number of risers = 15 or 16

Stair Calculation n Height of riser n n Example: TOTAL RISE inches Divide by number of risers Each riser must be equal in height 106. 25” / 15 n TOTAL RISE = 7. 08”

Stair Calculation n Ensure accuracy of riser and tread dimensions n One less tread than risers

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

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