Spray-Applied Fireproofing Thickness Calculator

Calculate required spray-applied fire-resistive material (SFRM) thickness for steel members per UL Design Listings and ASTM E119

Input Parameters

Results

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Required SFRM Thickness
in
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Required SFRM Thickness
mm
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Approximate Weight
psf
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Material Density
pcf
Note: W/D ratio is the key parameter - heavier sections with smaller exposed perimeters need less fireproofing. Always reference specific UL design listing numbers for the actual SFRM product being used. Minimum thickness applies regardless of W/D.

Reference

UL Fire Resistance Directory / ASTM E119 Empirical: t = (c1*R + c2)/(W/D + c3) W/D = weight-to-heated-perimeter ratio (lb/ft per ft) Higher W/D = thicker steel = less SFRM needed Cementitious SFRM: ~22 pcf density Mineral fiber: ~15 pcf density ASTM E119 standard fire exposure (ISO 834)