Jonathan Ochshorn
How 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:
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 |
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:
In general, any permitted hole must be separated from (cannot be continuous with) any other hole that links to another floor.
© 2010–2018 Jonathan Ochshorn. First posted July 27, 2012; last updated Nov. 8, 2018.