Stair Details

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Stair Details

Stair Widths
Diagram comparing multiple measured widths of stairs with a single person for scale

Stair widths are based on the use and occupancy loads of adjacent spaces and must be serviced with handrails on one or both sides depending on the stair width. For stairs serving a single user (typically private residential), a minimum of 36” | 91 cm is required. In general public spaces a minimum of 44” | 112 cm must be met—providing ample space for one person and allowing the tight passage of two people. Comfortable two person stair widths range between 49” | 125 cm to 60” | 152 cm. For three simultaneous users, a minimum of 74” | 188 cm is recommended. Handrails must be placed every 60” | 152 cm.

Consult the building code for details on specific occupancy loads.

Collection of dimensioned stair widths with people ranging from 1 person to 3 person widths
Stair widths are based on the use and occupancy loads of adjacent spaces and must be serviced with handrails on one or both sides depending on the stair width. In general public spaces a minimum of 44” | 112 cm must be met. Handrails must be placed every 60” | 152 cm.

Collection of dimensioned stair widths with people ranging from 1 person to 3 person widths
Stair Widths
Height:
Width:
Length:
Depth:
Weight:
Area:

1 Person (Private): 36” | 91 cm
1-2 People (Min. Public): 44” | 112 cm
2 People: 49” | 125 cm
2 People (Comfortable): 60” | 152 cm
3 People: 74” | 188 cm
Human Body Accommodation: 22” | 56 cm

Drawings include:
Stair Widths front elevations, front (people)

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Stair Risers & Treads
Diagram illustrating the standard dimensions of stair risers, treads, and nosings

Responding to the movement of the human body, the sizes and relationships of stair risers and treads are regulated to make vertical motion safe and easy. Steep stairs make climbing more tiring and dangerous, while shallow stairs are awkward and inefficient for our human stride. Buildings codes have been created to control the minimum and maximum measurements of risers and treads.

As general rules of thumb for achieving comfortable relationships between riser and tread dimensions, the following formulas can be used:

Tread (inches) + 2x Riser (inches) = 24”-25” (26” for exterior stairs)
Riser (inches) x Tread (inches) = 72”-75”

Responding to the movement of the human body, the sizes and relationships of stair risers and treads are regulated to make vertical motion safe and easy. Steep stairs make climbing more tiring and dangerous, while shallow stairs are awkward and inefficient for our human stride.

Stair Risers & Treads
Height:
Width:
Length:
Depth:
Weight:
Area:

Riser Height: 4" | 100 mm min.; 7" | 180 mm max.
Tread Depth:
11" | 280 mm min.
Nosing Protrusion: 
1.5" | 38 mm max.
Nosing Radius: .5" | 13 mm max.

  • Riser and tread dimensions should be continuously uniform for safety; building codes limit variation to 3/8" | 10 mm
  • The underside of risers should be sloped or have a 60° angle minimum between nosings and the horizontal surface
  • Open risers are not allowed under ADA guidelines
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