Common Path of Egress Travel in IBC 2018: Limits by Occupancy

Under the 2018 International Building Code, the common path of egress travel is capped at 75 feet for most occupancies in unsprinklered buildings, with increases to 100 feet (and up to 125 feet for some residential groups) when a qualifying sprinkler system is installed, and tighter limits of 25 feet for the most hazardous occupancies. The specific number depends on occupancy group, occupant load, and whether the building is sprinklered throughout. Table 1006.2.1 is where every answer lives, and the rest of this article walks through how to read it.

What the Code Is Measuring

Section 202 of the 2018 IBC defines common path of egress travel as the portion of exit access travel distance measured from the most remote point in a room or space to the point where occupants gain separate access to two exits or two exit access doorways.¹ It is the single-direction stretch at the start of an evacuation: if a fire blocks that lone path before an occupant reaches a point with two choices, there is no alternative route. The code treats that stretch as the riskiest phase of egress and caps it more aggressively than overall travel distance.

Measurement starts at the most remote occupied point on a floor and follows the centerline of the natural walking path, curving around walls, columns, and fixed equipment.² It is not a straight line on a plan. The measurement ends at the point where the occupant first has a genuine choice between two independent paths leading to two separate exits. A room with only one door contributes its entire depth to the common path, because no directional choice exists until the occupant passes through that door into a corridor with two directions available.

Maximum Distances by Occupancy

Table 1006.2.1 sets the limits by occupancy group, splitting unsprinklered buildings into two tiers based on whether the space holds 30 or fewer occupants.²

Unsprinklered Buildings

Assembly (A), Educational (E), Mercantile (M), and Factory (F) occupancies are capped at a flat 75 feet regardless of occupant count. The code gives these groups no occupant-load bonus.

Business (B), Storage (S), and Utility (U) occupancies work on a sliding scale. With 30 or fewer occupants, the common path can run to 100 feet. Above 30 occupants, the limit drops to 75 feet. A small office suite with 25 workers gets the extra 25 feet; an open-plan floor with 40 people does not.

Sprinklered Buildings

When a building has a full automatic sprinkler system installed throughout per NFPA 13 or NFPA 13R, several groups gain additional common-path distance. Partial installations do not qualify.² The increases are not uniform:

Groups B, F, and S get 100 feet with a qualifying sprinkler system. For B and S, this eliminates the occupant-load penalty that applies in the unsprinklered table.
Group I-3 (detention facilities) also gets 100 feet with sprinklers.
Groups A, E, and M stay at 75 feet. Sprinklers buy no additional common-path distance in schools, assembly spaces, or retail.
Group U actually stays at 75 feet when sprinklered, meaning the small-occupancy unsprinklered allowance of 100 feet is more generous than the sprinklered allowance.

Groups That Can’t Have a Common Path Without Sprinklers

Several occupancy groups show “NP” (Not Permitted) in the unsprinklered column of Table 1006.2.1. For these groups, any common path at all requires a full sprinkler system.

Residential (Group R)

Hotels and motels (R-1) allow a 75-foot common path with sprinklers. Apartments (R-2) get 125 feet, on the logic that residents know the layout of their own building. Groups R-3 (one- and two-family dwellings) and R-4 (residential care) also get 125 feet with sprinklers, though the common path requirement only applies to R-3 when the dwelling is part of a mixed-occupancy building.² A standalone single-family home does not need to comply with this measurement.

Institutional (Group I)

Hospitals, nursing homes, and similar facilities (I-1, I-2, I-4) are capped at 75 feet with sprinklers. Group I-3 detention and correctional facilities get 100 feet, reflecting that movement in those buildings is staff-controlled. Section 407.4 imposes additional travel distance restrictions on Group I-2 beyond what Table 1006.2.1 shows on its own.

High-Hazard Occupancies and Open Parking Garages

Buildings handling explosive, highly flammable, or toxic materials face the strictest limits. Groups H-1, H-2, and H-3 allow a maximum common path of just 25 feet, and only with a sprinkler system designed to Section 903.2.5 standards. No unsprinklered common path is permitted.² Groups H-4 and H-5 are less restrictive at 75 feet with sprinklers, but still require sprinklers for any common path.

Group S-2 open parking garages carry their own footnote. The common path cannot exceed 100 feet regardless of whether sprinklers are present, because open-air structures dissipate smoke and heat faster than enclosed buildings.

Common Path Is Not the Same as a Dead-End Corridor

The two concepts overlap enough to cause real design errors. Common path is the distance from the most remote point in a space to where an occupant first has two directional choices. A dead-end corridor is a corridor segment with no outlet, where an occupant who enters it must turn around to reach an exit.

Section 1020.4 caps dead-end corridors at 20 feet by default, far shorter than any common path limit.² Three exceptions relax the 20-foot rule:

In sprinklered buildings of Groups B, E, F, I-1, M, R-1, R-2, S, and U, dead ends can extend to 50 feet with a full NFPA 13 system.
In Group I-3 (Conditions 2, 3, or 4), dead ends can reach 50 feet.
No dead-end length limit applies when the dead-end corridor is shorter than 2.5 times its narrowest width.

Common path applies inside rooms and spaces as well as corridors. Dead-end limits apply only to corridor segments. A large room with a single door always generates common path distance but never triggers the dead-end rule. A corridor can trigger both if occupants must travel through it before reaching a point with two exit routes.

Common Path Inside Total Exit Access Travel Distance

Common path is a subset of exit access travel distance, not a separate measurement. Exit access travel distance runs from the most remote point all the way to the nearest exit, meaning a door to an exit stairway, exit passageway, or the building exterior. Common path is the opening segment of that total, the part where only one direction is possible.

Table 1017.2 sets the overall limits, and they are considerably longer. A sprinklered Group B building allows 100 feet of common path within a 300-foot total exit access travel distance.³ A sprinklered Group A building allows 75 feet of common path within a 250-foot total. Both limits must be satisfied independently. A design that meets the total travel distance but exceeds the common path still fails. You cannot borrow distance from the remaining budget to extend the single-direction segment.

When a Second Exit Becomes Required

Table 1006.2.1 does double duty. It governs the common path distance and the occupant-load trigger for requiring a second exit or exit access doorway. Exceeding either threshold means the space needs two exits. The occupant-load caps:²

Groups A, B, E, F, M, and U: single exit allowed for up to 49 occupants.
Group S: up to 29 occupants.
Groups R-2, R-3, and R-4: up to 20 occupants.
Groups I-1, I-2, I-3, I-4, R-1, H-4, and H-5: up to 10 occupants.
Groups H-1, H-2, and H-3: up to 3 occupants.

A space that stays under both the occupant-load cap and the common path distance limit can function with a single exit. The moment either threshold is exceeded, a second exit or exit access doorway is required. Common path distance is usually the binding constraint in large open floor plans; occupant load is usually the binding constraint in smaller high-density spaces like conference rooms or daycare areas.

1
International Code Council. 2018 International Building Code – Chapter 2 Definitions
2
International Code Council. 2018 International Building Code – Chapter 10 Means of Egress
3
International Code Council. 2018 International Building Code – Section 1017.2 Limitations