Disclosure. Design My Stair & Rail is an independent planning and cost-estimation resource. We are not a stair manufacturer, railing manufacturer, metal fabricator, architect, engineer, contractor, installer, code official, or permitting authority. Estimates and geometry are preliminary planning information, not bids, engineered designs, fabrication drawings, or code approvals. Final dimensions, structure, attachments, loads, guards, handrails, openings, materials, permits, and installation must be confirmed by qualified local professionals and the selected product manufacturer.
Guard versus handrail versus railing
A guard is a barrier that protects an open-sided walking surface. A handrail is a graspable element for support while using a stair. Railing is a broad consumer word that may mean either or both. One assembly can serve both functions, but a guard’s top rail is not automatically a compliant graspable handrail. A level guard runs along a floor, landing, or balcony; a stair guard follows the open side of a flight.
Residential and commercial code paths
In much of the United States, one- and two-family dwellings follow a residential code based on the International Residential Code (IRC), while multifamily, commercial, and public buildings follow a building code based on the International Building Code (IBC), plus accessibility requirements where applicable. The two paths differ on stair geometry, guard height, openings, and handrail details. This site’s planner is built for single-family residential projects and routes commercial and public projects to professional review.
Local code adoption and amendments
States and local jurisdictions adopt specific code editions on their own schedules and frequently amend them. Two neighboring towns may enforce different editions. Section numbers can also change between editions — for example, provisions in 2021 IRC Section R311.7 (stairways) and R312 (guards) moved to R318.7 and R321 in the 2024 IRC. Always confirm the edition and amendments with your building department. Official model-code text is available from ICC Digital Codes.
Rise and run, width, headroom, and landings
Common 2021 IRC model provisions, listed for education only. Every value is a model-code provision with exceptions; verify locally.
- Stair clear width
- 36 in minimum above the permitted handrail height; reduced clear width allowed at handrails2021 IRC R311.7.1 (2024 IRC R318.7.1) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Stair headroom
- 6 ft 8 in (80 in) minimum, measured vertically from the sloped plane of the tread nosings2021 IRC R311.7.2 (2024 IRC R318.7.2) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Riser height
- 7¾ in maximum; greatest riser may not exceed the smallest by more than ⅜ in within a flight2021 IRC R311.7.5.1 (2024 IRC R318.7.5.1) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Tread depth
- 10 in minimum, nosing to nosing; variation within a flight limited to ⅜ in2021 IRC R311.7.5.2 (2024 IRC R318.7.5.2) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Open risers
- Openings may not allow passage of a 4 in sphere where the stair’s total rise exceeds 30 in2021 IRC R311.7.5.1 (2024 IRC R318.7.5.1) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Maximum rise of a single flight
- 151 in (12 ft 7 in) between floor levels or landings2021 IRC R311.7.3 (2024 IRC R318.7.3) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Landings
- Landing at top and bottom of each stair; landing width not less than the stair width and at least 36 in in the direction of travel2021 IRC R311.7.6 (2024 IRC R318.7.6) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
Guard height and openings
- Where guards are required
- Open-sided walking surfaces, including stairs and landings, more than 30 in above the floor or grade below within 36 in horizontally2021 IRC R312.1.1 (2024 IRC R321.1) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Guard height
- 36 in minimum at level walking surfaces; 34 in minimum on open sides of stairs measured from the nosing line2021 IRC R312.1.2 (2024 IRC R321.2) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions. Commercial codes commonly require taller guards.
- Guard openings
- Openings may not allow passage of a 4 in sphere; 4⅜ in on open sides of stairs; 6 in at the triangular opening below the bottom rail2021 IRC R312.1.3 (2024 IRC R321.3) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions. Cable systems must also meet these limits under load, which depends on the manufacturer’s spacing and tensioning rules.
Handrail height and graspability
- Where handrails are required
- At least one side of each flight with four or more risers2021 IRC R311.7.8 (2024 IRC R320.1) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Handrail height
- 34 in to 38 in, measured vertically from the sloped plane of the tread nosings2021 IRC R311.7.8.1 (2024 IRC R320.2) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
- Handrail graspability
- Type I and Type II grip profiles with defined perimeter and cross-section limits2021 IRC R311.7.8.5 (2024 IRC R320.5) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions.
Continuity, returns, extensions, and clearance to the wall also matter and vary by code path.
Loads, glass, cable, and rod systems
Guards and handrails must resist specified loads, which in practice means the posts, connections, and the structure behind them. This site does not provide structural loads, anchor selections, glass thickness, cable tension, or fastener schedules. Those come from a selected manufacturer’s tested and documented system and, where required, project-specific engineering. Glass type and interlayer requirements are product- and code-path-specific. Cable and rod systems must keep openings within limits under load, which depends on the manufacturer’s spacing and post rules; some jurisdictions scrutinize horizontal infill.
Spiral stairs
- Spiral stairways
- 26 in minimum clear width; 6¾ in minimum tread depth at the walkline (walkline radius not more than 24½ in); 9½ in maximum riser; 6 ft 6 in minimum headroom2021 IRC R311.7.10.1 (2024 IRC R318.7.11.1) · International Code Council · Model-code provision; verify the locally adopted edition, amendments, and exceptions. Whether a spiral stair may serve as a required stair depends on the code path and the authority having jurisdiction.
Whether a spiral stair may serve as the required stair depends on the code path and local approval. Product-specific opening and diameter rules come from the manufacturer.
Exterior exposure
Exterior stairs and guards add wind, corrosion, drainage, freeze–thaw, and waterproofing considerations. Exterior attachment through decks and membranes must preserve waterproofing. Coastal sites call for marine-grade materials.
Accessibility in public and commercial projects
Public accommodations and commercial facilities may be subject to the 2010 ADA Standards for Accessible Design as well as local building codes. For contrast with residential values only:
- Stair risers and treads (public and commercial)
- Risers 4 in to 7 in; treads 11 in minimum; uniform within a flight2010 ADA Standards 504.2 · U.S. Department of Justice · Applies to accessible means of egress and covered facilities; local building codes also apply.
- Handrail height (public and commercial)
- 34 in to 38 in above stair nosings2010 ADA Standards 505.4 · U.S. Department of Justice · Applies to facilities covered by the ADA, not to single-family homes; listed for contrast only.
The planner does not evaluate ADA or IBC requirements. Commercial and public projects need a licensed design professional. See the ADA.gov design standards overview.
Manufacturer evaluation reports and AHJ review
Some products carry an ICC-ES evaluation report, a third-party listing, or published engineering that documents how they meet code when installed as specified. These help, but they do not replace project-specific review: the installation must match the report’s conditions, and the authority having jurisdiction makes the final decision. Bring the product’s installation manual and any evaluation report to your permit review.
Open-riser and open-guard designs may also deserve household review for children and pets, beyond what code requires.
Sources
Official sources are listed first. Model-code text is used only as educational context.
- ICC Digital Codes — current model-code text
- 2021 International Residential Code, Chapter 3 (Building Planning)
- 2021 International Residential Code, Section R311.7 (Stairways)
- 2024 International Residential Code, Chapter 3 (Building Planning)
- ADA design standards overview (ADA.gov)
- 2010 ADA Standards for Accessible Design