1409 Insulated Metal Panel (imp) — 2025 California Building Code

The provisions of this section, in addition to the other applicable requirements of this chapter and Chapter 16, shall govern the materials, construction and quality of insulated metal panels (IMP) for use as exterior walls and exterior wall coverings.

Structural design of IMP systems shall be in accordance with this section.

1409.2.1 IMP systems used as exterior walls. IMP systems used as exterior walls shall be designed and constructed to resist design loads in accordance with applicable provisions of Chapter 16.

1409.2.2 IMP systems used as exterior wall coverings. IMP systems used as exterior wall covering systems shall be designed and constructed to resist wind loads as required by Section 1609.

1409.2.3 Approval. Results of approved tests or engineering analyses shall be submitted to the building official to verify compliance with the applicable requirements of Chapter 16.

IMP systems shall comply with Section 1402 and shall be designed and constructed to resist wind and rain in accordance with this section and the manufacturer’s installation instructions.

IMP systems shall be constructed of approved materials that maintain the performance characteristics required in Section 1402 for the duration of use.

Evidence of the required fire-resistance rating of IMP systems shall be in accordance with this section.

EXTERIOR WALLS

1409.5.1 IMP used as exterior walls. In all types of construction where IMP systems are used as exterior walls required to have a fire-resistance rating in accordance with Section 705, evidence shall be submitted to the building official that the wall achieves the required fire-resistance rating.

1409.5.2 IMP used as exterior wall coverings. In all types of construction where IMP systems are used as exterior wall coverings on exterior walls required to have a fire-resistance rating in accordance with Section 705, evidence shall be submitted to the building official that the required fire-resistance rating is maintained.

Exception: IMP systems not containing combustible insulation, which are installed on the outer surface of a fire-resistance rated exterior wall in a manner such that the attachments do not penetrate to the entire exterior wall assembly.

IMP systems with noncombustible core insulation. IMP with noncombustible core insulation shall comply with Sections 1409.1 through 1409.5. Combustibility shall be determined in accordance with Section 703.3.

IMP systems with combustible core insulation shall comply with Sections 1409.1 through 1409.5 and this section. Combustibility shall be determined in accordance with Section 703.3.

1409.7.1 Surface-burning characteristics. Unless otherwise specified in this section, a combustible core 4 inches (102 mm) or less in thickness shall have a flame spread index of 75 or less and a smoke-developed index of 450 or less when tested in the maximum thickness intended for use in accordance with ASTM E84 or UL 723. For thicknesses greater than 4 inches (102 mm), the combustible core shall have a flame spread index of 75 or less and a smoke-developed index of 450 or less at 4 inches (102 mm) in thickness and the IMP approved based on testing in accordance with Section 1409.7.2.2 at the maximum IMP thickness intended for use.

1409.7.1.1 Foam plastic core. For IMP having a core insulation composed of foam plastic, the insulation core shall comply with Section 2603.3.

1409.7.2 Thermal barrier. Unless otherwise specified in this section, IMP with a combustible core shall be separated from the interior of a building by an approved thermal barrier consisting of 1/2-inch (12.7 mm) gypsum wallboard or a material that is tested in accordance with and meets the acceptance criteria of both the Temperature Transmission Fire Test and the Integrity Fire Test of NFPA 275.

1409.7.2.1 Foam plastic core. For IMP having a foam plastic core, use with the thermal barrier prescribed in Section 1409.7.2 shall be in accordance with Section 2603.4 unless special approval is obtained on the basis of Section 2603.9.

1409.7.2.2 Special approval. The thermal barrier specified in Section 1409.7.2 is not required where IMP is specifically approved based on tests conducted in accordance with, but not limited to, NFPA 286 (with the acceptance criteria of Section 803.1.1.1), FM 4880 or UL 1715. Such testing shall be performed with the IMP in a configuration related to the actual end-use and at the maximum thickness intended for use, and shall include seams, factory joints, sealants and other typical details intended for use.

1409.7.3 Type I, II, III, and IV construction. Where used as exterior walls or as exterior wall coverings on buildings of Type I, II, III and IV construction, IMP systems shall comply with this section as follows:

1. IMP having a foam plastic core shall comply with Section 2603.5.
2. IMP having combustible core other than foam plastic shall comply with Sections 1409.7.3.1 through 1409.7.3.4.

1409.7.3.1 Surface-burning characteristics. A combustible core not greater than 4 inches (102 mm) in thickness shall have a flame spread index of 25 or less and a smoke-developed index of 450 or less when tested in the maximum thickness intended for use in accordance with ASTM E84 or UL 723. For thicknesses greater than 4 inches (102 mm) the combustible core shall have a flame spread index of 75 or less and a smoke-developed index of 450 or less at 4 inches (102 mm) in thickness and the IMP approved based on testing in accordance with Section 1409.7.2.2 at the maximum IMP thickness intended for use.

1409.7.3.2 Thermal barrier. IMP shall be separated from the interior of a building by an approved thermal barrier in accordance with Section 1409.7.2.

1409.7.3.3 Vertical and lateral flame propagation. IMP installations greater than 40 feet (12 192 mm) in height above grade plane shall be tested in accordance with and comply with the acceptance criteria of NFPA 285. Such testing shall be performed on the exterior wall assembly and with the IMP in the maximum thickness intended for use.

1409.7.3.4 Ignition. IMP installations shall not exhibit sustained flaming where tested in accordance with NFPA 268. Where a material is intended to be installed in more than one thickness, tests of the minimum and maximum thicknesses intended for use shall be performed.

Exceptions:

Assemblies protected on the outside with one of the following:

1. A thermal barrier complying with Section 1409.7.2.
2. Concrete or masonry not less than 1 inch (25 mm) in thickness.
3. Glass-fiber-reinforced concrete panels not less than 3/8 inch (9.5 mm) in thickness.
4. Metal-faced panels having outer facings not less in thickness than 0.019 inch (0.48 mm) aluminum or 0.016 inch (0.41 mm) corrosion-resistant steel.
5. Stucco not less than 7/8 inch (22.2 mm) in thickness, complying with Section 2510.
6. Fiber-cement lap, panel or shingle siding complying with Section 1404.17 and Section 1404.17.1 or 1404.17.2, and having a thickness of not less than 1/4 inch (6.4 mm).

14-20 2025 CALIFORNIA BUILDING CODE

EXTERIOR WALLS

IMP shall be permitted for use in Type V construction.

Unless otherwise specified, the edge or face of each IMP or package shall bear the label of an approved agency. The label shall contain the manufacturer’s or distributor’s identification, model number, serial number or definitive information describing the product or materials’ performance characteristics and approved agency’s identification.

1409.9.1 Foam plastic core. IMP having a foam plastic core shall be labeled in accordance with Sections 2603.2 and 2603.5.6, as applicable.