6.4 Stairways: Treads, Risers, Nosings, Visual Contrast, and Lighting
Key Takeaways
A117.1 504.2 requires uniform risers 4 to 7 inches high and treads 11 inches deep; IBC 1011.5.4 limits variation within a flight to 3/8 inch.
Open risers are not permitted on accessible stairs (A117.1 504.3); IBC 1011.5.5.3 requires solid risers except on stairs not required to comply with 1009.3 where a 4-inch sphere cannot pass, and in limited occupancies.
A117.1 limits nosing radius and bevel to 1/2 inch, risers sloping back 30 degrees maximum, and nosing projection to 1 1/2 inches; the IBC limits projection to 1 1/4 inches and curvature to 9/16 inch.
A117.1-2017 requires a 1 to 2 inch contrasting stripe at the leading edge of every tread and landing (or durable warning markings required by the building code) and interior stair lighting of 1 footcandle idle and 10 footcandles in use.
Stairs need handrails on both sides complying with 505, and enclosed stairs need raised character and braille floor identification signs at each floor-level landing.
6.4 Stairways: Treads, Risers, Nosings, Visual Contrast, and Lighting
The Ramps, Stairways and Handrails subtopic (3%) in the General Site domain tests stairs that are part of an accessible means of egress or that the scoping provisions require to be accessible. A117.1 Section 504 sets the technical criteria, and IBC Section 1011 sets the general egress stair rules that apply at the same time. Where the two differ, the more restrictive rule governs the design.
Treads and Risers
| Item | A117.1 504 | IBC 1011.5 |
|---|---|---|
| Riser height | 4 in. min, 7 in. max, uniform (504.2) | 4 in. min, 7 in. max (1011.5.2) |
| Tread depth | 11 in. min, uniform (504.2) | 11 in. min (1011.5.2) |
| Uniformity | All steps in a flight uniform | Largest minus smallest riser or tread 3/8 in. max in a flight (1011.5.4) |
| Open risers | Not permitted (504.3) | Solid risers required (1011.5.5.3), with exceptions |
| Tread surface | Comply with 302; slope not steeper than 1:48 (504.4) | Not steeper than 1:48 (1011.7.1) |
IBC exceptions allow open risers on stairs not required to comply with 1009.3 where the opening does not pass a 4-in. sphere, in Group I-3, and in F, H and S occupancies other than areas accessible to the public, and on spiral stairs. A stair that serves as part of an accessible means of egress therefore always has solid risers.
Nosings (A117.1 504.5 and IBC 1011.5.5)
| Item | A117.1 504.5 | IBC 1011.5.5 |
|---|---|---|
| Uniformity | Nosings within a stairway uniform | Projections uniform, including the top landing |
| Rounded leading edge | Radius 1/2 in. max | Curvature or bevel 1/16 in. min, 9/16 in. max |
| Beveled leading edge | 45 degrees, extending 1/2 in. max horizontally | (within the 9/16 in. limit) |
| Underside of projecting nosings | Curved or beveled | - |
| Sloped risers | 30 degrees max from vertical | 30 degrees max from vertical |
| Projection | 1 1/2 in. max over the tread or floor below | 1 1/4 in. max beyond the tread below |
Apply both: an accessible stair with solid risers can project no more than 1 1/4 inches (IBC) and have a leading edge radius no more than 1/2 inch (A117.1).
Visual Contrast (A117.1 504.6, new in 2017)
Visual contrast complies with one of:
- The leading 1 to 2 inches of every tread and landing, measured from the leading edge of the nosing, is a solid color with dark-on-light or light-on-dark contrast from the rest of the tread; the durable marking extends from one side of each tread to the other; or
- Durable distinctive warning markings required by the adopted building code or an ANSI safety standard.
Other A117.1 504 Requirements
| Section | Requirement |
|---|---|
| 504.7 Handrails | Comply with 505 (both sides; see Section 6.5) |
| 504.8 Wet conditions | Treads and landings subject to wet conditions designed to prevent water accumulation |
| 504.9.1 Lighting levels | Interior stairs: 1 footcandle minimum when not in use and 10 footcandles minimum during use, measured at the center of treads and on landings within 24 in. of nosings; motion-sensor switching between them is allowed if fail-safe, activated by movement on the stair or landing, with timers of 15 minutes minimum |
| 504.9.2 Lighting controls | Occupancy sensing controls light the entrance landing, adjacent flights and landings above and below before any step is used |
| 504.10 Tactile signage within stair enclosures | Raised character and braille floor-level signs at each floor landing in enclosed stairways, next to the door into the corridor; the exit door to the outside or level of exit discharge has a raised character and braille "EXIT" sign |
| 504.11 Tactile signage at exits | Raised character and braille "EXIT" signs adjacent to doors to areas of refuge with stair access, exterior areas for assisted rescue, exit stairways, exit ramps, exit passageways and the exit discharge |
IBC Width, Headroom and Landings
| IBC section | Requirement |
|---|---|
| 1011.2 | Width per capacity, 44 in. minimum (36 in. where serving fewer than 50 occupants); stairs in an accessible means of egress comply with 1009.3 (48 in. between handrails unless sprinklered) |
| 1011.3 | Headroom 80 in. minimum |
| 1011.5.3 | Winder treads not permitted in means of egress stairways except within a dwelling unit |
| 1011.6 | Landings at top and bottom, as wide as the stair, depth equal to the stair width or 48 in., whichever is less; doors may not reduce the landing to less than half its required width and may project 7 in. max when fully open; wheelchair spaces for areas of refuge are outside the required landing width and doors may not swing over them |
Worked Example
A new two-story library's open exit access stair has 6 3/4-inch risers, 11-inch treads, open risers with 3-inch gaps, nosings that project 1 1/2 inches with a 1/4-inch radius, and no tread markings.
- Risers and treads comply (4 to 7 in., 11 in.).
- Open risers: if this stair is part of an accessible means of egress, A117.1 504.3 and IBC 1011.5.5.3 require solid risers; the 4-inch sphere exception does not apply to 1009.3 stairs.
- Projection: 1 1/2 in. meets A117.1 but exceeds the IBC 1 1/4 in. limit, so it fails.
- Visual contrast: a 1 to 2 inch contrasting stripe is required at the leading edge of each tread and landing under 504.6.
A new accessible stair has nosings that project 1 3/8 inches beyond the tread below. Which statement is correct?
It complies with both A117.1 and the IBC
It complies with the IBC but fails A117.1
It complies with A117.1 (1 1/2 inches maximum) but exceeds the IBC limit of 1 1/4 inches
It fails both because nosings may not project on accessible stairs
What does ICC A117.1-2017 Section 504.6 require at the leading edge of every tread and landing when the first visual contrast method is used?
A 3-inch yellow stripe on every other tread
A strip of photoluminescent tape 1 inch wide on every tread nosing
A raised abrasive strip 1/2 inch high
A 1 to 2 inch contrasting strip across each tread's leading edge
Under A117.1-2017 Section 504.9.1, what minimum illumination is required on an interior stair during conditions of stair use?
10 footcandles
1 footcandle
5 footcandles
20 footcandles
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