How are holes (vertical openings) made in floors (per IBC 2009)?

Jonathan Ochshorn

How are holes made in floors (per IBC 2009)? For a question so important in the design of buildings, the code answer is surprisingly difficult to track down. 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. 708. 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. 712; Sec. 712.4 requires that floor assemblies be continuous, and without openings, except where allowed in Sec. 712 (not relevant to our question), 708.2, 713.4, and 1022.1. What are those exceptions? IBC Sec. 708.2 contains a gold mine full of exceptions, that is, places where holes can be made in floors. The main exceptions (where holes are permitted in floor assemblies) fall into five categories, aside from covered mall buildings (IBC Sec. 402) which are not included in this discussion:

   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 floors 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 floors 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 non-sprinkered floor
   3. Hole connects only 2 floors and is part of means of egress (i.e., hole contains egress stair)
      • Not defined as an atrium
      • Not Group I or Group H
      • Per IBC Sec. 1016.1 exceptions 3 and 4, there must be at least two means of egress on the connected floors. In addition, the hole connects any two floors for up to 1/2 the exits (with maximum travel distance per non-sprinklered building); or, for sprinklered buildings only, connects bottom 2 floors for any number of exits (subject to max. exit access travel distance for sprinklered building).
      • Per IBC Sec. 1022.1, a hole is permitted for an unenclosed egress stair for less than 10 occupants and where one connected floor is at discharge level.
   4. Hole contains non-egress stair/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
      • No more than 4 connected stories (except Group B and Group M occupancies have no floor limits)
   5. Within dwelling units (Group R), holes connecting no more than 4 floors are permitted. 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) are not explicitly required to be met; instead, the requirements of either Sec. 708, or 713.4.2.1 and 713.4.2.2, must be met, if applicable. Sec. 713.4.2.1 and 713.4.2.2 are for penetrations, so they are not relevant to the question of making "architectural" holes in floors. Sec 708 describes where shaft enclosures are required; the exceptions are listed above. These exceptions seem to apply equally to all buildings, whether or not their floor assemblies are fire-resistance rated. This is puzzling, as the basic requirement for continuity of the horizontal assembly (Sec. 712) applies only to floors with a fire-resistance rating. Without this requirement for continuity, the requirement to comply with Sec 708 makes little sense: the implication is that the basic "continuity" requirement from Sec. 712 applies to all floor assemblies, even though non-fire-rated floors are specifically excluded from compliance with Sec. 712. I invite experts to contact me to clarify this point.
    
   [update 9/24/11] The 2009 International Building Code and Commentary contains an "unofficial" explanation within its commentary section that supports my assumption that continuity of horizontal assemblies must apply to all floor assemblies, whether or not they are fire-rated. The relevant commentary text, under Section 712.4 Continuity, is as follows: "The continuity provision applies regardless of whether a fire-resistance rating is required, since floor/ceiling assemblies are also intended to restrict vertical smoke movement..." I still cannot find anything in the Code itself that explicitly supports this reading, but the Commentary note is clear.

© 2010 Jonathan Ochshorn. First posted April 30, 2010; last updated September 27, 2011.