Jonathan Ochshorn
How does one make a vertical opening—a hole—in a single floor, or through multiple floors, while still being in compliance with the 2024 International Building Code (IBC)? This question is quite important, since architects like making holes in buildings. Even so, a code-compliant answer is surprisingly difficult to track down, especially since the fundamental fire-safety requirement for compartmentalization precludes the use of vertical openings and requires that all horizontal floor assemblies be continuous. In other words, at least at first glance, it appears that holes are not permitted at all.
Fortunately, this basic prohibition of vertical openings is modified in countless ways. Yes, code language in the 2024 IBC, found in Section 711.2.2, starts with the requirement for absolute continuity of fire-resistance-rated horizontal assemblies (so that a fire is more likely to be contained within its floor of origin), but a rather important exception immediately follows: "Assemblies shall be continuous without vertical openings, except as permitted by this section and Section 712." Practically speaking, Section 712 provides the architect with various ways to create vertical openings that, at least in theory, provide protection against the spread of fire in ways that are more-or-less equivalent to the ideal of continuity in fire-resistance-rated horizontal floor assemblies. (Nonfire-resistance-rated floor assemblies, per Section 711.3.2, have similar requirements for continuity and allow the same exceptions.)
Of course, one can always make a hole or "shaft" legal by protecting it with a "shaft enclosure"—such things are covered in Section 713. But to make a real hole in a floor—to visually and spatially connect two or more levels by removing a portion of a floor-ceiling assembly—one of the following six protection methods listed in Section 712 must, in general, be used:
712.1.1 Shaft enclosures. "Vertical openings contained entirely within a shaft enclosure complying with Section 713 shall be permitted."
712.1.2 Individual dwelling unit. "Unconcealed vertical openings totally within an individual residential dwelling unit and connecting four stories or less shall be permitted."
712.1.3 Escalator openings. "Where a building is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 [NFPA 13], vertical openings for escalators shall be permitted where protected in accordance with Section 712.1.3.1 or 712.1.3.2." These two alternate requirements are as follows: either (a) use automatic shutters at each floor; or (b) use draft curtains and closely spaced sprinklers while limiting the area of the opening to no more than twice the projected area of the escalator. Except in Group B and M occupancies, where the escalator opening can connect an unlimited number of floors, no more than four floors can be connected.
712.1.7 Atriums. "Atriums complying with Section 404 that connect two or more stories in Group I-2 or I-3 occupancies or three or more stories in other occupancies shall be permitted." But there are exceptions: atriums are not permitted in Group H occupancies; and atriums are effectively rendered unnecessary within the large assembly spaces found in Group A-1, A-4, and A-5 occupancies, since—in those occupancies and in the context of this section only—balconies, stories, and mezzanines are not considered to be stories. In other words, such spaces have, by definition, only 1 story, and opening protection is not required since there can be no openings in a space with only one floor level!
712.1.9 Two-story openings. "In other than Groups I-2 and I-3, a vertical opening that is not used as one of the applications specified in this section [e.g., is not an atrium, escalator opening, etc.] shall be permitted if the opening complies with all of the following items: (1) Does not connect more than two stories. (2) Does not penetrate a horizontal assembly that separates fire areas or smoke barriers that separate smoke compartments. (3) Is not concealed within the construction of a wall or a floor/ceiling assembly. (4) Is not open to a corridor in Group I and R occupancies. (5) Is not open to a corridor on nonsprinklered floors. (6) Is separated from floor openings and air transfer openings serving other floors by construction conforming to required shaft enclosures."
712.1.12 Exit access stairways and ramps. "Vertical openings containing exit access stairways or ramps in accordance with Section 1019 shall be permitted."
I've left out the following eight protection methods in Section 712.1 from my calculator because they are either routine or don't have much impact on the architectural design process:
712.1.4 Penetrations.
712.1.5 Joints.
712.1.6 Ducts and air transfer openings.
712.1.8 Masonry chimney.
712.1.10 Parking garages.
712.1.11 Mezzanine.
712.1.13 Openings "for floor fire doors and access doors…"
712.1.15 Skylights.
If you're wondering why mezzanines are on my second list, it isn't because mezzanines do not have an impact on the architectural design process. Rather, it is because a mezzanine, by definition, is "an intermediate level or levels between the floor and ceiling of any story and in accordance with Section 505." In other words, a mezzanine constitutes the addition of a partial level within a story; it is the insertion of this partial floor level between the floor and ceiling of a single story that causes the open space around it to become a vertical opening within that single story—the opening was not created by penetrating what would otherwise have been a continuous horizontal floor assembly. Yes, the space around a mezzanine connects two or more floor levels within a single story, and is therefore a "vertical opening." But mezzanines present no opening-specific complications. As long as the mezzanine-specific requirements in Section 505 are met, the opening formed by the addition of a mezzanine is compliant. This is not to say that mezzanines present no complications as mezzanines. On the contrary, architects have found creative ways to sabotage the intent of the code with respect to mezzanine design. See my analysis of noncompliant openings, mezzanines, and atriums in OMA's Milstein Hall at Cornell University for an example!
But back to my first list: perhaps the most common protection method for vertical openings is the shaft enclosure. Often surrounding the vertical openings that contain fire stairs, for example, such a protection method makes visual connections more difficult (although fire-rated glass can be used). Where the vertical opening needs to be actually open, one can use one of the other protection methods in the first list, e.g., two-story openings or atriums.
But things are not so simple: it turns out that there are other limitations and allowances for vertical openings in Chapter 4 of the IBC where we learn, for example, that vertical openings cannot be made in Group I-2 occupancies, but can be made—without employing any particular protective methods—in Group S-2 open parking garages. The contradictions between Section 712, which specifies permitted protection methods for vertical openings, and the occupancy-specific rules in Chapter 4, which may well contain different stipulations, can be incredibly confusing. This is because only some of the apparent contradictions are cross-referenced or explicitly resolved.
For example, IBC Section 408.5 (Protection of vertical openings) states that, for Group I-3 occupancies: "Any vertical opening shall be protected by a shaft enclosure in accordance with Section 713, or shall be in accordance with Section 408.5.1," which limits protection methods for I-3 occupancies to specific conditions that do not include atriums. However, the atrium protection method in Section 712.1.7 specifically allows atriums to be used in I-3 occupancies, seemingly in contradiction to the limits outlined in Section 408.5.1. The following question therefore arises: Would other protection methods not included in Section 408.5.1, but listed in Section 712.1.13 (Escalator openings) or Section 712.1.11 (Mezzanines) also be permitted for Group I-3 occupancies, since—even though they seem to contradict the limits on protection methods for Group I-3 occupancies found in Section 408.5.1—there is nothing in Section 712.1.13 or Section 712.1.11 that precludes the use of these protection methods in any particular occupancy group?
A similar question applies to Group I-2 occupancies, where Section 407 (Group I-2) requires horizontal assemblies, per Section 407.5.5, to resist the movement of smoke. This seems to be in contradiction to the atrium provisions in Section 712.1.7 which permit I-2 occupancies and which do not provide for barriers that "resist the movement of smoke" as required in Section 407.5.5—on the contrary, atriums encourage the movement of smoke away from occupied areas! So, once again, would Section 712.1.3 (Escalator openings) or Section 712.1.11 (Mezzanines) also apply to Group I-2 occupancies, since there is nothing in Section 712.1.3 or Section 712.1.11 that precludes the use of these protection methods for Group I-2 occupancies?
I've discussed such contradictions with a representative from the International Code Council (the authors of the IBC) and, based on these discussions, arrived at the following tentative conclusions, which are embedded in my vertical opening calculator: atriums can be used in Group I-2 and I-3 occupancies, since these two occupancy groups are specifically mentioned in Section 712.1.7, which permits the use of atriums as an opening protective method. But what about placing exit access stairs or ramps in an atrium within a Group I-2 or I-3 occupancy? Section 1019.1 (Exit access stairways and ramps, exception 5) allows such stairs and ramps in atriums, but excludes Group I-2 and I-3 occupancies. So, atriums are okay, but exit access stairs and ramps are not, even in a Group I-2 or I-3 atrium. What about escalators in a Group I-2 or I-3 atrium? Well, such devices are not used for egress, and there is no apparent rule that would prevent them from being placed in an atrium, even in a Group I-2 or I-3 occupancy. However, the stipulations in Section 407 for Group I-2 occupancies preclude openings (except, as we have seen, openings configured as atriums), so escalators outside of an atrium would not be permitted. Section 408 for Group I-3 occupancies permits vertical openings only under very specific conditions; if these conditions are met, it seems logical to allow escalators within such permitted openings, since there are no rules elsewhere in the code that would explicitly prohibit them.
Now you may be wondering why anyone would want to design an escalator in a Group I-2 hospital or a Group I-3 jail. But this misses the point: the code should clearly indicate what is, and what is not, permitted for every possible occupancy and situation, based on both fire science and empirically derived rules. Leaving such questions unresolved and confusing fosters a culture in which fire safety issues, in particular, are ignored or misunderstood. And, anyway, who says that an escalator would never be desired in a hospital or a jail?
The moral of this story is therefore that one must read the entire IBC when designing vertical openings in buildings. Whether these openings are permitted or not can depend on numerous variables described in Section 712, including the occupancy group, the number of stories connected by the opening, and the nature of the protection method chosen. All of this, of course, is subject to potentially contradictory stipulations found elsewhere in the code, especially in Chapter 4. And it is also important to examine Chapter 9 to determine what, if any, sprinkler requirements may apply.
My vertical opening calculator doesn't include every possible building type (e.g., I've left out covered mall buildings and underground buildings), but it's a good way to get some preliminary information about the feasibility of vertical openings in most other situations, taking into account not only the protection methods listed in Section 712, but also many of the stipulations found in Chapter 4, and the requirements for automatic sprinkler systems found in Chapter 9.
© 2024 Jonathan Ochshorn. First posted June 13, 2024; last updated June 13, 2024.