In addition to all of the other basic fire-resistant construction requirements found in Section R302 of the 2024 IRC, specific requirements for use of FPIS on exterior walls are found in Section R303. In summary, the requirements are as follows:
- Labeling and identification – required on FPIS material or packaging; refer to Section R303.2.
- Surface burning characteristics – required; maximum flame spread index and smoke-developed index of 75 and 450, respectively (unless tested per Section R303.6); refer to IRC Section R303.3.
- Thermal barrier – required for wood frame walls; typically not less than ½-inch-thick gypsum wallboard on interior side of wall or assembly tested per NFPA 275; refer to Section R303.4.
- Specific requirements – cover a range of specific applications to masonry or concrete construction, roofing, attics, crawlspaces, doors, backer-board, re-siding, and other applications; refer to IRC Section R303.5.
DESIGN RESOURCES: For additional information on fire safety compliant design of exterior wall assemblies of Type V wood-frame construction with FPIS ci, refer to the DrJ Research Report: Foam Plastic Insulating Sheathing Products in Type V Construction.
IMPORTANT TIP: FPIS manufacturers often conduct special code-compliance fire testing on their products to take advantage of the fire performance features of their specific FPIS products or assemblies. These may provide more efficient solutions, such as allowing use of FPIS without a separate thermal barrier or ignition barrier in certain applications.
CONSULT MANUFACTURER DATA: For product specific data and manufacturer support related to fire safety, refer to this listing of FPIS manufacturers.
NEXT STEP: With fire-safety provisions addressed in the specification of the FPIS material properties and other components of the wall assembly (e.g., thermal barrier), proceed to STEP 3.