IBC Stairway Standards

Stair Section Design Guidelines

• Open risers are permitted, but the opening must not allow a 102 mm sphere to pass through.
• Recommendations for steps: minimum tread depth of 33cm, adding riser lights or warning strips, and handrails for visual cues.

IBC Standards for Stairs

• Maximum distance between landing: 366 cm, with a suggested distance of 274 cm (especially for physically disabled people).
• Winder stairs have "pie-shaped" steps substituted for a landing, used when space is limited.

Spiral Stair vs. Curved/Circular Stair

• Spiral Stair:
  • Tread Width: 66 cm (min)
  • Tread Depth: 19.1 cm (after 30 cm from inner railing)
  • Riser Height: 24 cm (max)
  • Head Room: 198.1 cm
• Curved/Circular Stair:
  • Tread Width: 91.4 cm (min)
  • Tread Depth: 28 cm (after 30 cm from inner railing)
  • Riser Height: 17.8 cm (max)
  • Head Room: 200 cm

Headroom and Stair Nosing

• Headroom: vertical distance above stairs from a line drawn from nosing to nosing to finished upper construction.
• Stair nosing: maximum 30-degree angle.

Handrail Design

• Good gripping is essential; circular shape is best for gripping.
• Handrail clearance: 3.8 cm space between handrail and wall surface with a diameter of 3.2 to 5.7 cm.

Enclosed Exit Stairways and Guards

• Guards help prevent people from falling into floor openings; top portion should discourage sitting.
• Guards are required around unenclosed openings, landings, ramps, and balconies more than 76cm above the floor below.
• Minimum height: 106.7 cm; gap should not be more than 10 cm in between ornamental patterns or intermediate rails.

Stair Design in Horizontal Layout

• Minimum stair width:
  • 91.4 cm (for 49 people or less)
  • 112 cm (more than 49 people)
  • 122 cm (area for evacuation assistance)
• Landing Depth: minimum stair width, but no need to be greater than 122 cm.
• Handrail projection: 11.4 cm (both sides).
• Handrail extension: 30.5 cm (after riser ends and before riser starts).

Stair Design in Vertical Layout

• Handrails must be provided on both sides of the stair (except in residential spaces).
• Minimum handrail height: 86 cm; maximum handrail height: 96 cm.
• Riser height: minimum 10 cm; maximum 17.8 cm.
• Tread depth: minimum 27.9 cm.
• Head room: minimum.

Riser and Tread Relationships

• The relationship between riser and tread can be represented by the formula: 2R + T = 63.5 cm
• This formula shows that the dimension of tread and riser are inversely proportionate

Calculation of Riser and Tread

• When the riser dimension reduces, the tread dimension increases, and vice versa
• Examples of calculations:
  • 2R + 30 = 63.5 cm, R = 16.75 cm
  • 2R + 33 = 63.5 cm, R = 15.25 cm
  • 2R + T = 63.5 cm, with different values of R and T

Calculation for Stair

• Total Run = No of tread x depth of tread + Landing run
• Examples of calculations:
  • Total Run = 20x30 + 252.8 = 852.8 cm = 8.528 m
  • Total Run = 20x30 + 182.8 = 782.8 cm = 7.828 m

Calculation of Narrow U Stair

• Floor to floor height = 450 cm
• Approximate riser height = 16 cm
• Depth of tread = 30 cm
• Number of user = 40, width of tread = 91.4 cm
• Calculations:
  • Number of riser = 28 nos.
  • Exact riser height = 16.07 cm
  • Number of tread = 25 nos.
  • Total Run = 21x30 + 284 = 914 cm

Factors Affecting Total Run of a Stair

• Depth of treads
• Height of risers
• Number of landings
• Floor to floor height
• Examples of calculations:
  • Total Run = 21x32 + 284 = 956 cm
  • Total Run = 21x28 + 284 = 872 cm