IBC 2024 Stair Requirements: Width, Rise, Run, Headroom, Handrails, and Guards

Under IBC 2024, a means-of-egress stairway generally must be at least 44 inches (1118 mm) wide, have risers between 4 and 7 inches (102 and 178 mm), rectangular treads at least 11 inches (279 mm) deep, and provide at least 80 inches (2032 mm) of headroom. Stair flights generally require handrails on each side.

Those values are not a complete stair determination. Required capacity can make a stair wider, a stair serving fewer than 50 occupants can qualify for a 36-inch minimum, an accessible means-of-egress stair can have a separate 48-inch-between-handrails condition, and residential, spiral, assembly, institutional, and existing-building stairs have scoped exceptions or separate provisions.

IBC 2024 stair checklist

This table is an orientation. Apply the complete section, its exceptions, the adopted code edition, and local amendments before making a project decision.

Stair width requires both a capacity check and a minimum-width check

Section 1011.2 says stair capacity is determined under Section 1005.1 and then establishes a general minimum width of 44 inches. Its first exception permits 36 inches where the stair serves an occupant load of fewer than 50. The exception changes the prescriptive minimum; it does not waive a larger capacity-based width.

For capacity, Section 1005.3.1 generally uses 0.3 inch per occupant for stairways. The conditional 0.2-inch-per-occupant factor applies only where all stated conditions are satisfied, including the specified automatic sprinkler protection and emergency voice/alarm communication system, and it is unavailable for Groups H and I-2. Sprinklers alone do not establish the reduced factor.

Determine the occupant load, establish the required exits, calculate egress capacity, and then compare the capacity result with the stair minimum. Do not select 36 or 44 inches from occupant load alone and stop the analysis.

Where the stair is part of an accessible means of egress, Section 1009.3.2 generally calls for 48 inches clear between handrails. That provision includes exceptions for specified sprinklered buildings and stairways accessed from an area of refuge in conjunction with a horizontal exit. Chapter 11, ICC A117.1 where invoked, and applicable accessibility law remain separate coordination checks.

Riser height and tread depth

IBC 2024 Section 1011.5.2 establishes the general stair geometry:

• riser height: 7 inches maximum and 4 inches minimum; and
• rectangular tread depth: 11 inches minimum, measured horizontally between the vertical planes of the foremost projections of adjacent treads and perpendicular to the nosing.

The widely repeated 7 3/4-inch riser and 10-inch tread values are not the general commercial IBC rule. They appear in a scoped exception for Group R-3, qualifying dwelling units in Group R-2, and related Group U conditions. Other exceptions address spiral stairs, stepped aisles, replacement stairs under the IEBC, and specified Group I-3 stairs. Confirm that every condition of an exception applies before using its dimensions.

A correct rise-and-run example

For a simple floor-to-floor stair with a total rise of 108 inches:

1. Divide by the general 7-inch maximum: 108 ÷ 7 = 15.43.
2. Round up to 16 risers. Rounding to 15 would produce 7.2-inch risers and exceed the general maximum.
3. Calculate the actual uniform riser: 108 ÷ 16 = 6.75 inches.
4. A simple flight in which the upper floor or landing forms the terminal walking surface typically has 15 treads. At the general 11-inch minimum, its horizontal tread run is 165 inches, before adding landings.

The layout can change with intermediate landings, floor assemblies, finished surfaces, and special stair configurations. Use finished-floor elevations, not an unfinished structural dimension, when establishing the final riser sequence.

Dimensional uniformity is a flight-level check

Section 1011.5.4 requires treads and risers to be uniform in size and shape. Within a flight, the difference between the largest and smallest riser height cannot exceed 3/8 inch (9.5 mm), and the same maximum variation applies to tread depth. Winder geometry has its own uniformity provision and exceptions.

That tolerance is not permission to design one intentionally short or tall riser. It limits variation after the applicable minimum and maximum dimensions are satisfied. Coordinate finish thickness at both ends of the flight so the bottom and top risers are not changed by later flooring work.

Headroom is measured from the nosing line

Section 1011.3—not Section 1011.4—requires at least 80 inches (2032 mm) of stair headroom measured vertically from a line connecting the nosings. The clearance continues above the stair to the point where that line meets the landing below, one tread depth beyond the bottom riser, and it must be maintained across the full stair and landing width.

Spiral stairways complying with Section 1011.10 have a 78-inch exception. A second narrowly scoped exception addresses specified R-2, R-3, and Group U floor-opening conditions. Beams, ducts, soffits, and opening framing must be checked against the applicable measurement line; a generic rough-opening allowance does not prove compliance. The stair headroom checker evaluates this one bounded dimension and does not certify the entire stair.

Landings and vertical rise between landings

Section 1011.6 requires a floor or landing at the top and bottom of each stairway. The landing width, measured perpendicular to travel, must be at least the width of the stair served. Its minimum depth, measured parallel to travel, equals the stair width or 48 inches (1219 mm), whichever is less.

A door cannot reduce a stair landing below one-half its required width and, when fully open, cannot project more than 7 inches into the required landing width. Required wheelchair spaces under Section 1009.6.3 cannot occupy the required landing width, and doors cannot swing over those spaces. The section contains specific landing exceptions for stepped aisles and particular curved or turning configurations.

Section 1011.8 limits a stair flight to 12 feet (3658 mm) of vertical rise between floor levels or landings, except for the identified spiral stairs serving technical production areas.

Handrails are generally required on both sides

IBC 2024 Section 1011.11 requires handrails on each side of a stair flight and directs them to Section 1014. The old statement that one handrail is enough for a stair with four risers, or that two are required only when a stair exceeds 44 inches, is not the general 2024 IBC rule.

Listed exceptions include flights within dwelling units and spiral stairs, which may have a handrail on one side, and several narrowly defined changes in elevation. Apply an exception only to the occupancy and geometry it describes.

Key Section 1014 checks include:

• Height: 34 to 38 inches above the line connecting stair nosings under Section 1014.2.
• Graspability: a Type I circular handrail has a 1 1/4- to 2-inch outside diameter; noncircular Type I profiles have specified perimeter and cross-section limits under Section 1014.4.1.
• Continuity: gripping surfaces generally remain continuous under Section 1014.5, subject to its exceptions.
• Extensions: where rails are not continuous between flights, Section 1014.7 generally requires at least 12 inches horizontally beyond the top landing nosing and a continuation at the stair slope for one tread depth beyond the bottom tread nosing. The rail must return to a wall, guard, or walking surface, or continue to an adjacent flight.
• Wall clearance: 1 1/2 inches minimum under Section 1014.8.
• Intermediate rails: Section 1014.10 can require intermediate handrails so all portions of the required stair width or capacity are within 30 inches of a handrail.

See the separate guard and handrail guide for the relationship between the graspable rail and fall-protection barrier.

Guards use a separate trigger and geometry

A handrail assists travel on a stair; a guard limits falls from an open side. One assembly can sometimes perform both functions, but the applicable height, graspability, opening, load, and exception rules must all be satisfied.

Under Section 1015.2, guards are generally required along open-sided walking surfaces—including stairs and landings—located more than 30 inches (762 mm) vertically above the floor or grade below at any point within 36 inches (914 mm) horizontally of the open edge. Section 1015.3 generally requires a 42-inch guard measured from the line connecting the nosings on stairs.

The 42-inch value has scoped exceptions, including selected R-2 and R-3 conditions where 36 inches or 34 to 38 inches can apply. Do not characterize 36 inches as merely “the IRC number”; the IBC itself contains residential exceptions.

Section 1015.4 generally prevents passage of a 4-inch (102 mm) sphere through guard openings. Its exceptions include:

• a 4 3/8-inch sphere from 36 to 42 inches above the walking surface;
• a 6-inch sphere at the triangular opening formed by a stair riser, tread, and bottom rail; and
• a 4 3/8-inch sphere at the open sides of stairs in the specified R-2 and R-3 dwelling conditions.

There is no universal 4 3/8-inch “stair rake” rule for every IBC stair. Select the opening limitation by the exact location and occupancy condition.

What this guide does not size

Chapter 10 establishes egress geometry and related operational requirements; it does not provide a universal stringer size, rough-opening addition, header schedule, reinforcement layout, or connection detail. Structural design depends on loads, spans, materials, construction type, fire-resistance requirements, Chapter 16, applicable material chapters and standards, and the project’s engineered details.

Accordingly, this guide does not prescribe 2×12 stringers, a 3 1/2-inch residual stringer depth, double-LVL headers, generic reinforcing at every tread, or one concrete nosing detail. Those former recommendations were not general IBC 2024 minima. Coordinate structural capacity, fire protection, accessibility, slip resistance, walking-surface construction, guards, handrail loads, and local amendments with the responsible design professionals and authority having jurisdiction.

Continue the means-of-egress sequence with the corridor guide, egress-door guide, and IBC resource hub.

Primary source and scope

• 2024 International Building Code, Chapter 10 — Means of Egress

This guide describes the unamended 2024 model IBC. It does not determine the adopted code, local amendments, occupancy, construction type, accessibility scope, structural design, or approval for a specific project.

Correction history

• 2026-08-31: Replaced the unsupported construction sequence with a bounded IBC 2024 stair guide; corrected the general riser maximum from 7 3/4 to 7 inches, the headroom citation to Section 1011.3, the handrail rule to both sides with scoped exceptions, the handrail and guard section references, the guard-opening exceptions, landing dimensions, and the rise/run example; removed generic stringer, header, reinforcement, and concrete-nosing prescriptions.