3.1 Accessible Route Scoping, Components, Slopes, and Clear Width
Key Takeaways
IBC 1104.1 requires an accessible route from public transportation stops, accessible parking, accessible passenger loading zones and public streets or sidewalks to the accessible entrance served.
IBC 1104.4 Exception 1 releases stories with an aggregate area of 3,000 square feet or less, but not for M with five or more tenants, health care offices, transportation facilities, government buildings or structures with four or more dwelling units.
Accessible route walking surfaces have a running slope not steeper than 1:20 and a cross slope not steeper than 1:48; steeper running slopes are ramps.
A117.1-2017 requires 36-inch interior and 48-inch exterior accessible routes; 32-inch point reductions up to 24 inches long must be separated by 52-inch segments in new buildings (48 inches existing).
Routes narrower than 60 inches need passing spaces at 200-foot maximum intervals; new 180-degree turns around objects less than 52 inches wide use 36/60/36, 42/48/42 or 43/43/43 widths.
3.1 Accessible Route Scoping, Components, Slopes, and Clear Width
Accessible Routes is the largest domain on the ICC 21 exam (27%). This section covers the scoping that decides where routes are required (IBC 1104) and the technical rules every route segment must meet (A117.1 Sections 402 and 403). Doors, ramps, curb ramps, elevators and lifts follow in later sections.
IBC 1104: Where Accessible Routes Are Required
| Section | Requirement |
|---|---|
| 1104.1 Site arrival points | At least one accessible route within the site from public transportation stops, accessible parking, accessible passenger loading zones, and public streets or sidewalks to the accessible building entrance served. Exception: other than in buildings containing or serving Type B units, no route is needed if the only access between them is a vehicular way not providing for pedestrian access. |
| 1104.2 Within a site | At least one accessible route connects accessible buildings, facilities, elements and spaces on the same site (same vehicular-way exception; recreational facilities only as required by 1111). |
| 1104.3 Connected spaces | At least one accessible route to each portion of a building required to be accessible, to accessible entrances connecting accessible pedestrian walkways, and to the public way. Exceptions: stories exempted by 1104.4; assembly levels with fixed seating that have no wheelchair spaces; elevated courtroom employee work stations under 1109.4.1.4; recreational facilities as limited by 1111. |
| 1104.3.1 | Common use circulation paths in employee work areas (see Section 1.1). |
| 1104.3.2 Press boxes | Must be on an accessible route, except press boxes in bleachers with a single point of entry, or free-standing press boxes more than 12 ft above grade, where the aggregate press box area per playing field is 500 sq ft or less. |
| 1104.4 Multistory | At least one accessible route connects each accessible story, mezzanine and occupied roof. |
| 1104.5 Location | Routes coincide with or are in the same area as general circulation paths; interior circulation needs an interior route; where only one route exists, it may not pass through kitchens, storage rooms, restrooms, closets or similar spaces (a kitchen or storage room in an Accessible, Type A or Type B unit is allowed). |
| 1104.6 Security barriers | Bollards and checkpoints may not obstruct accessible routes or accessible means of egress; a route beside a metal detector is allowed if users keep visual contact with their belongings. |
The Multistory Exceptions (1104.4)
- Stories, mezzanines and occupied roofs with an aggregate area of not more than 3,000 sq ft located above and below accessible levels. This exception does not apply to: multiple-tenant Group M facilities with five or more tenant spaces where at least one is above or below the accessible level; stories containing offices of health care providers (Group B or I); passenger transportation facilities and airports; government buildings; and structures with four or more dwelling units.
- Stories, mezzanines or occupied roofs that contain no accessible elements or spaces required by Sections 1108 or 1109.
- The cab of an air traffic control tower and the floor immediately below it.
- A two-story building where one story or mezzanine has an occupant load of five or fewer and contains no public use space.
A117.1 Section 402: Route Components
An accessible route consists of one or more of: walking surfaces with a running slope not steeper than 1:20, doors and doorways, gates, ramps, curb ramps (excluding flared sides), blended transitions, elevators and platform lifts. Revolving doors, revolving gates and turnstiles are not part of an accessible route (402.3); an accessible door or gate must be provided beside them.
A117.1 Section 403: Walking Surfaces
| Rule | Section | Requirement |
|---|---|---|
| Surface | 403.2 | Comply with 302 (stable, firm, slip resistant) |
| Slope | 403.3 | Running slope not steeper than 1:20; cross slope not steeper than 1:48 |
| Changes in level | 403.4 | Comply with 303 (1/4 in. vertical, 1/2 in. beveled) |
| Handrails | 403.6 | Where handrails are required at the side of a corridor, they comply with Sections 505.4 through 505.9 |
A walking surface steeper than 1:20 is a ramp (A117.1 definition) and must comply with Section 405. A path that rises 15 inches over 24 feet (288 inches) has a slope of 15/288 = 1:19.2, which is steeper than 1:20, so it is a ramp needing landings and, because the rise exceeds 6 inches, handrails.
Clear Width (403.5)
| Condition | Requirement (A117.1-2017) |
|---|---|
| Interior accessible route | 36 in. minimum |
| Exterior accessible route | 48 in. minimum |
| Exterior route within seating areas | 36 in. minimum |
| Exterior ramp | Clear width per 405.5 (36 in.) |
| Point reduction, new buildings | 32 in. minimum for 24 in. maximum length; reduced segments separated by segments 52 in. long and 36 in. wide |
| Point reduction, existing buildings | 32 in. for 24 in. maximum; separated by segments 48 in. long and 36 in. wide |
180-Degree Turns (403.5.2)
| Condition | Requirement |
|---|---|
| New, object 52 in. or wider | Normal widths of 403.5.1 apply through the turn |
| New, object less than 52 in. wide | One set of approach/during/leaving widths: 36/60/36, 42/48/42, or 43/43/43 in. |
| Existing, object less than 48 in. wide | 42/48/42 in.; not required where the width during the turn is 60 in. |
90-Degree Turns (403.5.3)
New buildings use one of four sets: both legs 40 in. wide maintained for 28 in. from the inner corner; both legs 36 in. where the interior corners are chamfered 8 in. along both walls; one leg 42 in. and the other 38 in.; or one leg 44 in. and the other 36 in. Turns at doors complying with 404.2.3 and at elevators or lifts complying with 407 to 410 are exempt. Existing buildings require 36 in. legs.
Passing Spaces (403.5.4)
Where a route is less than 60 in. wide, passing spaces are required at 200 ft maximum intervals. A passing space is either a 60 x 60 in. space or an intersection of two walking surfaces forming a T-shaped turning space whose base and arms extend 52 in. (new, using a 304.3.2.1 T) or 48 in. (existing) beyond the intersection.
Worked Example
A new office corridor is 40 inches wide and 260 feet long, with one structural column narrowing it to 33 inches for 18 inches of length.
- The 40-inch interior width exceeds 36 inches.
- The column creates a point reduction: 33 inches is at least 32 inches and 18 inches is no more than 24 inches, so it complies. A second reduction would need at least 52 inches of 36-inch-wide corridor between them.
- At 260 feet long and less than 60 inches wide, the corridor needs passing spaces at intervals of 200 feet maximum, for example a 60 x 60 alcove or a qualifying T intersection.
Exam Traps
- Exterior accessible routes are 48 inches wide in A117.1-2017, not 36 (IEBC 306.7.6 allows 36 inches for exterior routes in alterations).
- New-building point reductions use 52-inch separations.
- Passing spaces are 403.5.4 in the 2017 edition.
- The 3,000 sq ft multistory exception is an aggregate area test, and government buildings cannot use it.
A new two-story government office building has an upper floor of 2,400 square feet. Under IBC 1104.4, is an accessible route required to the upper floor?
No, because the story has an aggregate area of not more than 3,000 square feet
No, because two-story buildings never require elevators
Yes, because the 3,000 square foot exception does not apply to government buildings
Yes, but only if the occupant load of the upper floor exceeds 50
What is the minimum clear width of a new exterior accessible route that is not within a seating area, under ICC A117.1-2017 Section 403.5.1?
48 inches
36 inches
44 inches
60 inches
In a new building, an accessible corridor narrows to 32 inches at two columns, each for 20 inches of length. What is the minimum length of the 36-inch-wide segment required between the two reductions?
24 inches
36 inches
48 inches
52 inches
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