The International Building Code (IBC) sets the maximum stair riser height at 7 inches (178 mm) and the minimum stair tread depth at 11 inches (279 mm) (IBC Section 1011.5.2). Handrails must be installed on stairways at a height between 34 inches (864 mm) and 38 inches (965 mm) above the stair nosing (IBC Section 1011.11; ADA Section 505.4). These rules, often referred to as the stair riser height code and the handrail height code, are the foundation of safe stair and ramp design in the U.S.

Why stair riser height and handrail height matter

Occupant safety

• Uniform riser and tread dimensions reduce falls. The IBC stair code requires riser height consistency and a minimum stair tread depth so users can maintain rhythm and stability when ascending or descending.
  
• Handrails at the correct height provide balance and support. The ADA and IBC handrail code requirements ensure they are usable for both adults and people with mobility impairments.
  
• Stair width code ensures enough space for normal circulation and emergency evacuation.
  

Emergency egress

• Wide stairways, proper landings, and continuous stair handrail height compliance make mass evacuation possible during fires or disasters (IBC Section 1011.2, Section 1011.6).
  
• Inconsistent step riser height or missing stair rails can slow movement and cause dangerous surges.
  

Durability & maintenance

• Exterior stair railing code requires corrosion-resistant handrails; interior stairs need smooth, graspable handrails.
  
• Proper stair rise and run reduce unusual wear on materials, lowering lifecycle costs.
  

Compliance & liability

• A missed minimum stair tread depth or stair railing height code violation can trigger failed inspections, delays, or even lawsuits.
  
• Accessibility lawsuits often cite violations of ADA stair requirements, including maximum riser height and proper ramp handrails.
  

Lessons from history: Why codes exist

• Cocoanut Grove fire (Boston, 1942): Nearly 500 lives lost, partly due to non-compliant exits and stairways. Today’s stair width minimums and exit stairway rules stem from this disaster.
  
• 1970s–80s slip and fall lawsuits: Inconsistent step riser height codes and missing handrails drove IBC reforms to mandate uniformity and proper stair railing codes.
  
• ADA adoption (1990): Federal law established the maximum slope for ramps (ADA Section 405.2) and handrail height for stairs (ADA Section 505.4) to ensure accessibility.
  
• Stadium crowd disasters: Crushed stairways and bottlenecks in large venues led to today’s stair landing size and stair width code requirements for assembly occupancies.
  

Stakeholder perspectives

• Architects: See stairs as both functional and aesthetic but must comply with standard stair riser height, stair rail height, and minimum tread depth codes.
  
• Engineers: Ensure structural safety, verifying handrail anchorage meets load requirements (IBC Section 1607).
  
• Contractors: Work with tolerances; even a ½-inch error in riser height can mean rework.
  
• Inspectors: Enforce stair head clearance, minimum stair width, stair tread depth standards, and railing height code.
  
• Manufacturers: Produce modular stair and handrail systems tested against ASTM and UL slip resistance and durability standards.
  

Material performance and broader building goals

• Resilience: Non-slip coatings, corrosion-resistant exterior stair handrails, and uniform stair tread sizes extend service life.
  
• Sustainability: Longer-lasting stair assemblies reduce replacements and carbon footprint.
  
• Lifecycle cost: Designing stairs to meet maximum riser height, minimum tread depth, and stair handrail height code lowers liability, change orders, and lawsuits.
  
• Accessibility: Proper stair and handrail design makes buildings inclusive for people with disabilities and older adults.
  

Key code requirements

Dimensions

• Maximum stair riser height: 7 in (178 mm) – IBC Section 1011.5.2
• Minimum stair riser height: 4 in (102 mm) – IBC Section 1011.5.2
• Minimum stair tread depth: 11 in (279 mm) – IBC Section 1011.5.2
• Stair width minimum: 36 in (914 mm) in most occupancies; 44 in where occupant load >50 – IBC Section 1011.2

Landings

• Landing size: Depth must be ≥ stair width (not less than 48 in in most cases) – IBC Section 1011.6

Handrails

• Handrail height for stairs: 34–38 in (864–965 mm) above nosing – IBC Section 1011.11; ADA Section 505.4
• Handrail grip: Circular: 1¼–2 in diameter; Noncircular: perimeter 4–6¼ in; wall clearance ≥1½ in – IBC Section 1014.3

Guards

• Guardrail height: 42 in (1067 mm) minimum for open sides – IBC Section 1015.3

Key takeaways

• Maximum stair riser height is 7 inches; minimum stair tread depth is 11 inches (IBC Section 1011.5.2).
  
• Handrail height must be between 34 and 38 inches above stair nosings (IBC Section 1011.11; ADA Section 505.4).
  
• Codes evolved from real disasters—every rule prevents repeat tragedies.
  
• Compliance improves safety, durability, sustainability, and reduces liability.
  

References

• IBC 2024: https://codes.iccsafe.org/content/IBC2024V1.0
  
• IRC 2024: https://codes.iccsafe.org/content/IRC2024V1.0
  
• California Building Code (CBC 2025): https://codes.iccsafe.org/content/CABC2025P1
  
• New York State Building Code (2020): https://codes.iccsafe.org/content/NYSBC2020P1
  
• Florida Building Code (2023): https://codes.iccsafe.org/codes/florida
  

FAQs

1. What is the maximum stair riser height allowed by code?
The IBC stair riser height code sets the maximum riser height at 7 inches (178 mm) (IBC Section 1011.5.2).

2. What is the minimum stair tread depth required?
Stair tread code requires a minimum tread depth of 11 inches (279 mm) (IBC Section 1011.5.2).

3. What is the required handrail height for stairs?
Handrails must be between 34–38 inches (864–965 mm) above the nosing of stair treads (IBC Section 1011.11; ADA Section 505.4).

4. Are handrails required on both sides of stairs?
Yes, the stairway handrail code requires handrails on both sides of stairways in most occupancies (IBC Section 1011.11; ADA Section 505.2).

5. What is the minimum stair width according to code?
The stair width code requires at least 36 inches (914 mm), or 44 inches (1118 mm) if the occupant load exceeds 50 (IBC Section 1011.2).

6. What are common stair code violations?
Typical violations include inconsistent riser heights, insufficient tread depth, stair railing installed outside the 34–38 in range, lack of graspable handrails, inadequate stair landing size, and missed stair head clearance.