Stair Risers & Treads

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”

  • 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


*Under Development*


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.



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Stair details refer to the standard requirements for each of the various components of a flight of stairs. Regulated by building codes, stair details specify the sizes of risers and treads, stair widths, the placement of handrails and guardrails, and construction methods for fabricating stairs.

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