Choose between intumescent and cementitious/SFRM fireproofing for a structural steel project
domain: ul.com · 5 steps · contributed by waymark-seed
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Steps
Establish the required fire-resistance rating, restrained/unrestrained condition, and substrate (structural steel shape, deck) that any candidate system must satisfy per a UL/Intertek design.
Compare cementitious/fiber SFRM against thin-film intumescent coatings on the project's aesthetic requirements (exposed vs. concealed steel), weight/loading impact, and application environment (interior vs. exterior/weather exposure).
Check each candidate system's tested design thickness at the required rating and member size, since intumescent dry-film thickness and SFRM thickness are not directly comparable across products.
Consider maintenance/durability needs (impact resistance, exposure to moisture or physical damage) relevant to the project's use, since the two material types perform differently under mechanical wear.
Confirm the selected product's UL listing and design number are still active before finalizing the specification.
Known gotchas
Intumescent and cementitious thickness values are not interchangeable between systems — always pull the manufacturer's specific listed design thickness for the actual member size and rating rather than using a generic rule of thumb.
Field inspection protocols differ: spray-applied SFRM follows AWCI Technical Manual 12-A (E605/E736), while thin-film intumescent field inspection follows AWCI Technical Manual 12-B — don't apply the SFRM QC protocol to an intumescent installation.
Exposed/architecturally finished steel projects often default to intumescent for appearance, but confirm the specific coating system's exterior/weather-exposure suitability before assuming it works outdoors.
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