Where a wood-frame building does not satisfy the scope limits of the 2024 IRC, the fire-safety provisions of the 2024 IBC must be used. In addition to all other basic fire-safety requirements in the IBC (e.g., Chapters 3-10) and requirements for exterior walls (Chapter 14) and roofs (Chapter 15), specific requirements for use of FPIS are found in Chapter 26, particularly Section 2603.
In accordance with IBC Chapter 6, all light-frame wood construction is identified as “Type V” which, among other things, limits building heights and areas when using this type of construction. These limits and other requirements mentioned above are intended to limit risk and consequences of fire given that wood is a combustible material. Consequently, the provisions in IBC Section 2603 that apply to use of FPIS ci on exterior walls of Type V construction are summarized as follows:
- Foam Plastic Materials and Standards – refer to IBC Section 2603.1.
- Labeling and identification – required on materials or packaging; refer to IBC Section 2603.2.
- Surface burning characteristics – required; maximum flame spread index and smoke-developed index of 75 and 450, respectively (with various exceptions); refer to IBC Section 2603.3.
- Thermal barrier – required; typically not less than ½-inch-thick gypsum wallboard on interior side of wall or assembly tested per NFPA 275 (with various applications and conditions where thermal barrier is not required); refer to IBC Section 2603.4.
- Roofing – foam plastic insulation meeting the above requirements is permitted as part of a roof covering assembly (e.g., above-deck roof insulation) where the roof assembly with the foam plastic insulation is a Class A, B, or C roofing assembly per ASTM E108 or UL 790; refer to IBC Section 2603.6 and Section 1505 where the required fire classification depends on the building’s construction type.
DESIGN RESOURCES: For additional information on fire safety compliant design of exterior wall assemblies with FPIS-ci, refer to:
IMPORTANT TIPS:
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.
The additional provisions of IBC Section 2603.5 for exterior walls of buildings of any height, do not apply to Type V (typically wood frame) construction. For example, the NFPA 285 vertical and lateral fire propagation test is not required because fire risk is adequately mitigated by other requirements for or limits of use of Type V construction. For information on types of construction where the provisions of IBC Section 2603.5 do apply, refer to the DrJ Research Report: Foam Plastic Insulating Sheathing Products in Type I, II, III or IV Construction. Note that steel, concrete, and masonry construction may be used in Type V construction and avoid the requirements of IBC Section 2603.5 provided the building meets all the requirements for and limitations of use for Type V construction.
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 decisions of STEP 2 addressed by specification of the FPIS material properties and other components of the wall assembly (e.g., thermal barrier) applicable to Type V construction, proceed to STEP 3. See STEP 2A for decisions regarding one- and two-family dwellings (≤ 3 stories).