Beginning with the 2012 International Residential Code (IRC), lightweight framing (I-Joists, plated trusses, etc) not required elsewhere in the code to be fire-resistant rated, shall be provided with a 1/2" gypsum wallboard membrane, 5/8" wood structural panel membrane, or equivalent on the underside of the floor framing members.
For additional information, see the following:
2012 IRC - Section R501.3
2015/2018 IRC - Section R302.1.3
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