How Much Does Structural Steel Fireproofing Cost?

Structural steel fireproofing runs about $2–$9 per square foot of steel surface for cementitious spray (SFRM) on concealed steel, and $4–$12 per square foot for thin-film intumescent on ordinary building steel. Where the steel is exposed and has to look finished, intumescent climbs to $15–$40, and medium- or high-density cementitious for garages, plant rooms and industrial areas runs $7–$20+.

Which of those numbers applies is a choice between technologies, so that comes first.

First, a correction: “spray-applied” is not a third technology

Cost guides often list “cementitious, intumescent and spray-applied fireproofing” as three options. They are not. SFRM stands for spray-applied fire-resistive material, and it covers two families:

• Cementitious SFRM — a gypsum or Portland-cement binder (roughly 50–80% by weight) mixed to a slurry and sprayed on. The workhorse of concealed building steel.
• Mineral-fiber SFRM — rock-wool fibre with a smaller cement binder (roughly 20–30%), conveyed dry and wetted at the nozzle. Low density and the least impact-resistant of the group.

Intumescent (IFRM, intumescent fire-resistive material) is a different technology — a thin coating that expands into an insulating char in a fire — and it is also usually sprayed. So the real comparison is cementitious vs intumescent, with board systems as a third, non-sprayed route.

Fireproofing cost by method

Installed planning ranges checked September 2026, per square foot of sprayed steel surface — not building floor area. Intumescent ranges match our intumescent fireproofing cost guide; SFRM density tiers from published 2026 contractor pricing. Published SFRM figures run from averages of about $2.40–$6 up to $5–$14 for commercial density: large, repetitive, unobstructed scopes land at the low end, while small or obstructed jobs reach the top. Treat these as a frame for a tender, not a quote.

Cementitious (SFRM) fireproofing cost

This is where most building fireproofing money is spent, and it prices differently from intumescent in two ways.

Density sets the price tier

SFRM is sold and specified by in-place density, and density follows where the steel lives:

pcf = pounds per cubic foot. Density and thickness are verified on site under ASTM E605 — contractors commonly cite one density-and-thickness sample per 2,500 sq ft of sprayed area — which is itself a cost line on large jobs.

Higher density means a harder, more damage-resistant coat that survives knocks, humidity and washdown, and more material and slower application per square foot. The mistake to avoid runs both ways: commercial density in a parking garage fails early, and high density above a dropped ceiling is money spent on durability nobody will use.

Thickness is set by the building code — and it follows the beam

Required SFRM thickness comes from the tested UL design. When the actual beam differs from the one in the tested assembly, the International Building Code lets you adjust thickness by formula — IBC §722.5.2.2.1, Equation 7-17:

h₂ = [ (W₁/D₁ + 0.60) ÷ (W₂/D₂ + 0.60) ] × h₁

where h is SFRM thickness in inches, W is beam weight in lb per linear foot, D is the heated perimeter in inches, subscript 1 is the tested beam and subscript 2 is yours.

That formula is the cost story. W/D is the US form of the section factor: a light beam has little steel behind a lot of surface, heats faster, and needs more material. Taking an illustrative tested beam at W/D 0.84 with 1 inch of SFRM:

You can run this for your own beams with the SFRM thickness calculator, which enforces the code limits rather than returning a number for any input.

Arithmetic from the code equation with illustrative W/D inputs — one board foot is one square foot at one inch. The formula carries hard limits: the substitute beam's W/D must be at least 0.37, the calculated thickness at least 3/8 inch, the beam rating at least 1 hour, and for restrained beams it applies only to compact sections under AISC 360. Your UL design governs.

Read across the table: the lighter beam needs about 1.6× the material of the heavier one (1.31 in against 0.80 in) for the same rating on the same square foot. That is why two SFRM quotes for “1,000 square feet at 2 hours” can differ sharply — they may be pricing different steel.

Intumescent follows the same physics but not the same arithmetic: its dry film thickness comes only from each product's UL loading table, in mils, with no public code formula. The detail — including why the same square foot of intumescent can cost ten times more on one member than another — is in our intumescent fireproofing cost guide.

Why SFRM is cheaper — and where it is not acceptable

SFRM material is inexpensive and it builds inches of protection quickly, so labour per square foot is low on big, open, repetitive areas. Intumescent is the reverse: costly material in thin coats, multiple passes, cure times and detailed thickness inspection.

What SFRM cannot do is look finished. It is a rough, relatively soft texture up to a couple of inches thick, and it is easily damaged by later trades. On steel that architects want seen — lobbies, atriums, open-ceiling offices, schools — it is simply not an option, and the comparison never happens.

Spray-applied vs troweled vs board systems

Sprayed is the default for both SFRM and most intumescent work: fastest per square foot on large areas, but it needs masking, overspray control and clear access to the steel.

Troweled or hand-applied cementitious is used for patching and repairing sprayed coats after other trades damage them, small areas, and details a spray rig cannot reach. It is slower per square foot and priced accordingly — usually as touch-up allowance rather than area.

Board encasement — layers of Type X gypsum board or calcium silicate board fixed around a member — is a dry trade with no overspray, which suits columns in occupied or finished spaces. Type X gypsum board itself is inexpensive at roughly $0.65–$0.85 per sq ft of board as material, but installation is framing-and-fixing labour per member, so board systems are quoted per column or per linear foot rather than per sprayed square foot. Calcium silicate costs more than gypsum and is chosen for harder, more moisture-tolerant encasement.

What drives fireproofing cost

• Fire rating in hours. Each step up means more thickness — inches for SFRM, mils for intumescent.
• Section size. W/D for SFRM, section factor for intumescent: lighter members need more material.
• Density or finish requirement. Density class for SFRM; decorative topcoat and tolerances for exposed intumescent.
• Access. Deck height, obstructions and sequencing around MEP trades. Spraying at 20–40 ft with clear access is far faster than at 60 ft through ductwork.
• Fire curve. Hydrocarbon exposure (UL 1709) needs roughly 20–40% more intumescent thickness than building-fire ratings (UL 263) — see the intumescent cost guide.
• Scope size. Mobilisation and setup make small jobs expensive per square foot.

Which method for which project

Office, school and healthcare frames with dropped ceilings — commercial-density cementitious SFRM. The steel is hidden, appearance does not matter, and it is the lowest cost per square foot.

Parking structures, mechanical rooms, loading docks — medium- or high-density cementitious. The steel is exposed to knocks, moisture and washdown, and commercial density will not last.

Lobbies, atriums, open ceilings, architecturally exposed steel — thin-film intumescent. It costs more, but it is the only route that looks like paint. See what intumescent coating is for how it works.

Columns in occupied or finished spaces — board encasement, where overspray and wet trades are not welcome.

Refineries, LNG and offshore — thick-film epoxy intumescent to UL 1709, quoted per project.

How to get a fireproofing quote

Fireproofing contractors price from the drawings, not from a floor area:

1. The steel schedule — member sizes, so thickness can be calculated.
2. UL design numbers for each rated assembly, and the rating in hours.
3. Concealed or exposed — which decides SFRM versus intumescent, and the density class.
4. Deck and ceiling heights, plus access and sequencing constraints.
5. Scope boundaries — whether the metal deck is in the sprayed area, and who patches after other trades.

For how fireproofing contractors are selected and how the work is inspected, see the fireproofing contractors overview.

Got a steel package that needs a rating? Tell us the building type, the rating and whether the steel is exposed, and we'll route it to a fireproofing contractor who works to that spec.