/ Field knowledge · IMC 602.3.7–602.4
Foam in a return plenum needs the right test route.
Treat an exposed foam finish or trim as its own 2024 IMC 602.3.7 review. A 25/50 flame and smoke report alone does not qualify it: the same intended product configuration also needs the required room fire test or the specified IBC 2603.9 approval. Protected foam has a separate 75/450 plus barrier route. Plastic piping, insulation, discrete devices, and flood hazards each have separate rules.
Educational 2024 International Mechanical Code (IMC) 602.3.7-602.4 from Daily Code Talk. Confirm the edition adopted by the project jurisdiction. See the ICC model-code text for 602.3.7, the 602 overview, and duct flood 603.13. This page is not a product listing. Packet: English PDF · PDF en español.
- Exposed foam finish or trim, 602.3.7: At the maximum thickness and density intended for use, ASTM E84 or UL 723 must show flame spread ≤25 and smoke developed ≤50 and the foam must pass NFPA 286 using IBC 803.1.1 acceptance criteria. Approval from tests under IBC 2603.9 may replace the NFPA 286 test only; it does not replace the 25/50 test. The three protected-foam exceptions instead require ≤75 flame spread and ≤450 smoke at maximum intended thickness and density plus separation from plenum airflow by either an IBC 2603.4 thermal barrier, corrosion-resistant steel with base metal thickness ≥0.0160 in., or masonry/concrete ≥1 in. Document the exact product and installed assembly.
- 602.3.8 plastic plumbing piping and tubing: listed and labeled flame spread ≤25, smoke ≤50. Exception: UL 2846-listed water piping with defined smoke/flame performance.
- 602.3.9 listed pipe and duct insulation, adhesives, and coatings: ASTM E84 / UL 723 flame spread ≤25 and smoke ≤50 using ASTM E2231 specimen preparation and mounting; ASTM C411 must show no flaming, glowing, smoldering, or smoking at the service temperature, with test temperature at least 250°F. The insulation cannot be used to make an otherwise nonqualifying pipe or duct appear compliant unless the applicable composite assembly route is met.
- 602.3.10 other combustibles: listed and labeled 25 / 50. 602.3.6 discrete products: UL 2043 for plenum use (metallic electrical enclosures excepted).
- 602.4 flood hazard: plenums above IBC 1612 utility elevation, or resist water entry, hydrostatic, and buoyancy. Coordinate with Miami-Dade flood path.
Foam test report covers only one requirement
A 25/50 tunnel result without the separate NFPA 286 or IBC 2603.9 basis does not establish the exposed-foam route. A protected-foam exception also needs the 75/450 report and the specified continuous separator. Plastic pipe or a device needs its own applicable listing. Show the exact product and configuration before closing the ceiling.
Source: Daily Code Talk — IMC 602.3.7–602.4 · tool: Plenum-materials screen · wiring: 602.3 cable / sprinkler · 602: overview · ducts: 603.13.
What to send
Mark the actual return-air plenum, every exposed foam / pipe / insulation / device, the product reports at intended thickness and density, the installed barrier detail if claimed, and the IBC 1612 utility elevation where flood rules apply.
If the plenum material path is undocumented
Send the reflected ceiling plan, product listings and test reports, and any barrier details. MasterBuild can scope the open 602.3 material question and the separate 602.4 flood question.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
MasterBuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. Flame spread 25 / smoke 50, UL 2043, UL 2846, ASTM C411, 1-inch masonry barrier, and IBC 1612 are 2024 IMC 602 education from Daily Code Talk — not a materials listing. This page is not legal advice.