Stair Terminology and Common Building Codes

Stairs come in various designs, and while constructing a basic staircase may seem straightforward, it involves precise calculations and adherence to building codes. These regulations cover dimensions such as step length, width, height, door placement (doors must swing fully onto a landing, not over steps), and safety features. Below are key stair-related terms and standard building codes. Note: Local codes may vary, so always verify requirements for your specific area.

1. Run / Tread

• Definition: The horizontal part of a step where the foot is placed.
• Measurement: From the outer edge (including nosing, if present) to the riser.
• Total Run Calculation: The sum of all tread lengths, excluding the top tread and accounting for nosing overhang.
• Building Code: Minimum 10 inches (25.4 cm) per tread.

2. Rise / Riser

• Definition: The vertical height between two consecutive treads.
• Measurement: From the top of one tread to the top of the next (excluding tread thickness).
• Note: The number of steps in a staircase is determined by risers, not treads.
• Building Code: Maximum 7.75 inches (19.7 cm) per riser.

3. Nosing

• Definition: The protruding edge of a tread that extends over the riser below.
• Purpose: Enhances safety by providing additional foot space.
• Building Code:
  • Minimum projection: 0.75 inches (1.9 cm)
  • Maximum projection: 1.25 inches (3.2 cm)

4. Headroom

• Definition: The vertical clearance from a tread’s surface to the ceiling above.
• Purpose: Ensures safe passage for users and movement of large objects.
• Building Code: Minimum 6 feet 8 inches (203.2 cm).

5. Stair Width

• Definition: The horizontal distance between the two sides of a stairway (excluding handrails).
• Note: Typically, stair width is greater than tread length.
• Building Code: Minimum 36 inches (91.44 cm).

6. Handrails & Guards (Guardrails)

• Handrail: A rail for support when ascending or descending stairs.
• Guard: A protective barrier along elevated walkways to prevent falls (may be a rail, wall, or other structure).
• Building Code:
  • Guards required if stairs rise >30 inches (76.2 cm) above the floor.
  • Guard height: Minimum 34 inches (86.36 cm) from tread surface.
  • Handrail height: 34–38 inches (86.36–96.52 cm) from tread surface.
  • Handrail diameter: 1.25–2.675 inches (3.18–6.79 cm).

7. Stringer

• Definition: The structural support for treads and risers (typically two side stringers and one center stringer).
• Visibility: May be exposed (cut to step shape) or hidden (enclosed tread edges).

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Fraction to Decimal Conversion Table

16th	8th	4th	2nd	Decimal
1/16	–	–	–	0.0625
2/16	1/8	–	–	0.125
3/16	–	–	–	0.1875
4/16	2/8	1/4	–	0.25
5/16	–	–	–	0.3125
6/16	3/8	–	–	0.375
7/16	–	–	–	0.4375
8/16	4/8	2/4	1/2	0.5
9/16	–	–	–	0.5625
10/16	5/8	–	–	0.625
11/16	–	–	–	0.6875
12/16	6/8	3/4	–	0.75
13/16	–	–	–	0.8125
14/16	7/8	–	–	0.875
15/16	–	–	–	0.9375
16/16	8/8	4/4	2/2	1

This guide summarizes essential stair components and general code standards. Always consult local regulations for compliance.