707A.8 Underfloor Protection
The underfloor area of elevated or overhanging buildings shall be enclosed to grade in accordance with the requirements of this chapter or the underside of the exposed underfloor shall consist of one of the following:
- Noncombustible material
- Ignition-resistant material
- One layer of 5/8-inch Type X gypsum sheathing applied behind an exterior covering on the underside of the floor projection
- The exterior portion of a 1-hour fire resistive exterior wall assembly applied to the underside of the floor including assemblies using the gypsum panel and sheathing products listed in the Gypsum Association Fire Resistance Design Manual
- The underside of a floor assembly that meets the performance criteria in Section 707A.10 when tested in accordance with the test procedures set forth in ASTM E2957.
- The underside of a floor assembly that meets the performance criteria in accordance with the test procedures set forth in SFM Standard 12-7A-3.
Exception: Heavy timber structural columns and beams do not require protection.