The thermal barrier specified in Section R316.4 is not required where all of the following apply:
- Crawl space access is required by Section R408.4.
- Entry is made only for purposes of repairs or maintenance.
- The foam plastic insulation has been tested in accordance with Section R316.6 or the foam plastic insulation is protected against ignition using one of the following ignition barrier materials:
- 11/2-inch-thick (38 mm) mineral fiber insulation;
- 1/4-inch-thick (6.4 mm) wood structural panels;
- 3/8-inch (9.5 mm) particleboard;
- 1/4-inch (6.4 mm) hardboard;
- 3/8-inch (9.5 mm) gypsum board; or
- Corrosion-resistant steel having a base metal thickness of 0.016 inch (0.406 mm).