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How are holes (vertical openings) made in floors (per IBC 2012)?

Jonathan Ochshorn

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sketch showing hole in building floorHow are holes made in floors (per IBC 2012)? For a question so important in the design of buildings, the code answer is surprisingly difficult to track down (although the 2012 IBC is clearer than its predecessors). The basic idea seems to be that floors must be continuous (so holes cannot be made), except that this basic prohibition is modified in countless ways. Of course, one can always make a hole (shaft) and then protect it (shaft enclosure): such things are covered in IBC Sec. 713. But to make a hole in a floor — to visually and spatially connect two or more levels by removing a portion of a floor-ceiling assembly — one must follow this logic:

  1. We first start with the fundamental requirement for fire-resistance ratings on building elements, depending on construction type (IBC Table 601). Here, we see that "floor construction and secondary members" require a rating of anywhere from 0 to 2 hours.

    Required fire-resistance rating in hours
    Part of building I-A I-B II-A II-B III-A III-B IV V-A V-B
    Floor construction and secondary members 2 2 1 0 1 0 heavy timber 1 0

     
  2. Where a rated floor assembly is required (all construction types except II-B, III-B, and V-B, or Type IV heavy timber), the requirements for horizontal assemblies are contained in IBC Sec. 711; Sec. 711.4 requires that floor assemblies be continuous, and without openings, except where allowed in Sec. 712.1 (vertical openings), 714.4 (penetrations), 715 (joints), 1009.3 (exit access stairways), and 1022.1 (interior exit stairways and ramps). What are those exceptions? IBC Sec. 712.1 and 1009.3 contain a gold mine full of exceptions (actually no longer listed as "exceptions" as in the 2009 IBC, but rather listed as permitted vertical openings), that is, places where holes can be made in floors. The main instances where holes are permitted in floor assemblies fall into five categories; there may be other types of occupancies with special provisions for openings not included here:

    1. Atrium
      • Sprinklered
      • Not Group H
      • Covered space
      • Fire alarm and smoke control systems (smoke control not required for 2-story atrium)
      • Separation from adjacent spaces required except that sprinklered, gasketted glass frames are OK, or 3/4 hr rated glass block, or any 3 stories can be configured without separation from the atrium if smoke from such areas is accounted for in atrium calculations. Note that areas outside atrium need not be sprinklered if separated by 2-hr fire barriers or horizontal assemblies.
      • See IBC Sec. 404 requirements for details
    2. Hole connects only 2 stories and is not part of a means of egress
      • Not defined as an atrium
      • Not within I-2 or I-3 occupancy
      • Not open to a Group I or Group R corridor
      • Not open to any corridor on a nonsprinkered story
    3. Hole connects only 2 stories with an exit access stairway (per IBC Sec. 1009.3 exception 1)
      • Not defined as an atrium
      • Not Group I-2 or I-3
    4. Hole contains an exit access stairway or an escalator
      • Sprinklered
      • Not defined as an atrium
      • Projected (plan) area of stair/escalator is not less than 1/2 the hole area
      • Draft curtains and special sprinklers needed around hole perimeter
      • Unlimited number of stories can be connected for Group B and Group M occupancies; for all other occupancies, a maximum of 4 stories can be connected in this way
    5. Within individual dwelling units (all Group R except R-4), holes connecting no more than 4 stories are permitted, with or without stairs (whereas individual R-4 dwelling units can have a hole connecting no more than 4 stories, but only without a stair). Within housing units (Group I-3, see IBC Sec. 408.5), holes are permitted if four criteria are met: connected areas must be "open and unobstructed" for the benefit of supervisory personnel; exit capacity must be sufficient "for all occupants from all interconnected cell tiers and areas"; the maximum distance between the highest and lowest connected floors cannot exceed 23 ft; and egress "from any portion of the cell tier to an exit or exit access door shall not require travel on more than one additional floor level within the housing unit."

    In general, any permitted hole must be separated from (cannot be continuous with) any other hole that links to another floor.

  3. Where a rated floor assembly is not required (construction types II-B, III-B, and V-B, or Type IV heavy timber), the requirements for continuity of the floor assembly (IBC Sec. 712) still apply; nonfire-resistance-rated horizontal assemblies (711.1) must comply with 714.4.2 (penetrations) which in turn requires compliance with either 713 (shaft enclosures) or 714.4.2.1 (noncombustible penetrating items) or 714.4.2.2 (penetrating items).
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