Protection of vertical openings is a subject about which we receive a fair number of questions here at NFPA. In general, floors need to provide a smoke-resistant barrier between stories in a building to prevent smoke from migrating vertically and affecting occupants on stories other than the story of fire origin. A vertical opening is a “hole in the floor” that requires some form of protection. Different vertical openings have different names: convenience opening; communicating space; atrium; two-story opening with partial enclosure; and others. The varied protection strategies offered by the code are, I think, what creates some confusion. To determine the protection requirements, refer to Section 8.6 and the X.3.1 subsection of the applicable occupancy chapters. A quick overview of a few scenarios based on the 2018 edition of the code follows:
- Full enclosure: Where vertical openings (holes in floors) exist, enclose the openings with fire barriers on each story exposed to the opening. The required fire resistance rating of the enclosing barriers depends on the number of stories exposed to the opening(s) and whether it is new or existing. See 8.6.5 for the required rating. Examples include elevator hoistways and utility shafts. This scenario satisfies the base requirement of 8.6.2. Note that exit stair enclosures, which are a form of vertical opening, must meet the more stringent requirements of 18.104.22.168; meeting the exit enclosure requirements inherently meets the vertical opening requirements.
Where full enclosure on all exposed stories is not practical or is undesirable, the code offers several alternatives. These are referred to as continuity exemptions in 8.6.3; here are examples of a few of them:
- Partial enclosure: Where a vertical opening occurs in one floor only (i.e., only two stories are exposed to the opening), 8.6.8 permits the opening to be enclosed on one story or the other leaving one of the stories exposed to the opening. The required rating of the enclosing barriers is covered by 8.6.5 (1-hr for new, ½-hr for existing). No special occupancy chapter permission is required and there are no restrictions on what the opening can be used for. If the opening is used for a stair, the stair could be used as part of a required exit access, but it does not qualfiy as an exit since 22.214.171.124 and 126.96.36.199 require exit stairs to enclosed on every story (there is an exemption for some existing two-story exit stairs in 188.8.131.52.1.3).
- Convenience opening: Where a vertical opening occurs in one floor only (i.e., two stories are exposed to the opening), the opening might be permitted to be unenclosed on both stories if it meets the requirements of 184.108.40.206. These unenclosed openings require permission in the X.3.1 subsection of the applicable occupancy chapters, where X is the chapter number (e.g., 38.3.1 for new business occupancies. Some of the key requirements of 220.127.116.11 include: the opening can’t communicate with openings to other stories; new openings must be separated from any corridors (these convenience openings are sometimes found in office building tenant spaces); if the opening is used for a stair, the stair does not get any credit as a means of egress.
- Communicating space: These are sometimes referred to as “mini-atriums.” Unlike a convenience opening, a communicating space can expose up to three stories to each other. With the increased exposure comes additional requirements and limitations in 8.6.6. Communicating spaces are permitted unless prohibited by the X.3.1 subsection of the applicable occupancy chapters; for an example, see 18.104.22.168, which prohibits communicating spaces in new health care occupancies. Portions of stories that are exposed to the communicating space must be separated from the remainder of the building by fire or smoke barriers depending on whether the building is protected by automatic sprinklers. Areas outside the communicating space need access to an exit without passing through the communicating space, and the communicating space needs to be open and unobstructed so a fire on any story within the communicating space will be readily apparent. Contents within the communicating spaces are restricted to low hazard (essentially noncombustible) unless the space has automatic sprinklers. By meeting all the criteria in 8.6.6, the unenclosed floor are openings are protected.
- Atrium: Whereas a communicating space is limited to exposing not more than three contiguous stories, an atrium can expose any number of stories because it is subject to the stringent requirements of 8.6.7, which include automatic sprinkler protection throughout the building. New atriums must be provided with an engineering analysis to show that smoke from a fire in the atrium will not prevent the use of the highest exit access path exposed to the atrium for the time needed to evacuate; this frequently necessitates an engineered smoke control system. Think of a Hyatt or Embassy Suites hotel in which, upon leaving your guest room, you’re immediately in the atrium space. This exit access path needs to be maintained relatively smoke free to allow occupants to reach the enclosed exit stairs. The design of atrium buildings is largely performance-based and frequently involves computer fire and egress modeling.
The atrium at NFPA in Quincy, MA
The code offers a handful of additional vertical opening protection strategies – see Section 8.6 for the details. Be aware that some of the Life Safety Code vertical opening protection requirements might differ from those in the International Building Code; in some cases, the Life Safety Code might be more restrictive (several attendees at classes I’ve instructed have indicated this is the case for two-story, unenclosed vertical openings). Where a jurisdiction has adopted both NFPA 101 and the IBC, designers will likely need to comply with the more restrictive provisions so as to meet the requirements of both.
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