Construction glossary · Steel and structural
What is Fireproofing (SFRM) in construction?
Fireproofing (SFRM) is spray applied fire resistive material, a cementitious coating sprayed onto structural steel beams, girders, and columns so the assembly achieves a code required fire resistance rating, such as 1, 2, or 3 hours, under a listed UL design. The required thickness depends on the rating hours and the member's W/D ratio, roughly 1-1/2 inch for a 2 hour rating on a typical beam. Estimators take it off in square feet of steel surface area and price it per sf.
Updated June 2026 · Reviewed by the Ruh construction team
SFRM applied over steel
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Book a walkthroughSFRM stands for spray applied fire resistive material, the gray cementitious coating sprayed onto structural steel so a beam, girder, or column achieves the fire resistance rating the building code requires, typically 1, 2, or 3 hours per a listed UL design. The required rating lives on the architectural code summary and life safety sheets, the spec sits in Section 07 81 00 Applied Fireproofing, and the member sizes that drive thickness come from the structural framing plans. A specialty fireproofing subcontractor applies it, and the GC sequences it carefully because the spray has to happen after deck and steel are complete but before MEP trades fill the ceiling space. Thickness is not one number for the job: it depends on the rating hours and each member's W/D ratio, weight per foot over heated perimeter, so lighter members need thicker spray to reach the same rating. New estimators get burned three ways: pricing per ton of steel instead of per sf of surface area, assuming a single thickness for every member, and forgetting the patching adder after other trades hang supports from the sprayed steel.
SFRM is taken off in square feet of steel surface area at a stated thickness, and priced per sf. For beams, multiply the spray profile perimeter of the shape, a three sided contour where deck sits on the top flange, by the member length from the structural framing plans; columns use the full profile perimeter times height. Rating hours come from the code summary, and thickness comes from the UL design and the member's W/D ratio. Estimators group quantities into thickness bands, since 1 inch and 2-1/4 inch material do not cost the same per sf, then add overspray waste and a patching allowance for damage caused by following trades. The line lands in the estimate as sf by thickness band.
Worked example
Take a 2 hour rated floor with 24 W16x26 beams, each 30 ft long, under metal deck. Step 1, spray profile: a three sided contour on a W16x26 runs about 4.0 sf of surface per lf of beam (typical, derived from the shape perimeter). Step 2, area per beam: 4.0 sf per lf x 30 ft = 120 sf. Step 3, total: 120 sf x 24 beams = 2,880 sf at 1-1/2 inch thickness, the typical 2 hour requirement for a beam of this W/D under the governing UL design. Step 4, patching: hangers and penetrations installed after spray justify a 5 percent adder, so 2,880 sf x 1.05 = 3,024 sf, carried as 3,024 sf. Step 5, price it: at an illustrative $2.25 per sf for 1-1/2 inch cementitious SFRM, 3,024 sf x $2.25 = $6,804. A heavier beam earns the same rating at less thickness, so always quantify by thickness band, never one rate for the whole frame.
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How Ruh handles Fireproofing (SFRM)
Ruh reads the structural framing plans and code sheets, builds the SFRM takeoff by measuring beam and column surface areas at the required thickness, and prices the square footage against the contractor's own price book, the unit costs they actually buy fireproofing at. The estimator then reviews the thickness assignments and the patching allowance and signs off before the number goes into the bid.
See construction estimating softwareFireproofing (SFRM): frequently asked questions
How do I figure out what SFRM thickness a beam needs?+
Start with the rating hours on the architectural code summary, then find the listed UL design referenced in the spec or on the drawings. Each design publishes thickness as a function of the member's W/D ratio, weight per foot divided by heated perimeter, so a light beam might need 1-7/8 inch where a heavy girder reaches the same rating at 1 inch. Never apply one thickness across the whole frame; sort members into thickness bands before pricing.
Why is fireproofing taken off in square feet instead of tons of steel?+
Because the cost driver is sprayed surface area, not weight. A light beam has nearly the same perimeter as a heavy one of the same depth, so a job full of light framing carries far more sf per ton, and a per ton plug will underprice it. Measure profile perimeter times length for each member, keep the thickness with the quantity, and the number defends itself at bid review.
What is the patching adder and who pays for it?+
After spray is complete, mechanical, electrical, and fire protection trades hang supports from the steel and knock material off, and inspectors will flag bare spots before ceilings close. Most fireproofing subs carry a patching allowance, commonly a few percent of the base sf or a return trip crew cost, and GCs backcharge trades that cause damage beyond it. Carry it as a visible line in the estimate so it is not a fight during the job.
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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.