SFRM vs. Intumescent Fireproofing: A Contractor's Guide
How to choose the right fireproofing system for your commercial project — from cost and aesthetics to fire ratings and code compliance.
If you are a general contractor, architect, or project manager specifying fireproofing for a commercial building, you have two primary options for protecting structural steel: spray-applied fire-resistive material (SFRM) and intumescent coatings.
Both systems achieve the same fundamental goal — they insulate steel from fire so it maintains structural integrity for a rated duration. But they work differently, they cost very different amounts, and they are appropriate for different situations. On most commercial projects, the answer is not one or the other — it is a deliberate combination of both.
This guide breaks down the key differences so you can make an informed decision at the plan review stage, before pricing starts.
What Is SFRM (Spray-Applied Fireproofing)?
SFRM stands for spray-applied fire-resistive material. It is a cementitious or fiber-based material that is spray-applied directly onto structural steel beams, columns, and metal decking. The result is a thick, textured coating — typically ranging from 1/2 inch to over 2 inches depending on the required fire rating and the steel section size.
In the construction industry, SFRM is often referred to simply as "Monokote" — a brand name from Grace/GCP Applied Technologies that has become synonymous with the product category. Other widely used products include BlazeShield II from Isolatek International (Cafco) and Monokote MK-6. All commercial SFRM products must be UL-classified and tested to meet fire resistance requirements specified by the International Building Code (IBC).
SFRM is the workhorse of commercial fireproofing. It is applied rapidly with specialized spray equipment, it bonds directly to the steel substrate, and it is by far the most cost-effective method of protecting structural steel from fire. The tradeoff is appearance: SFRM has a rough, textured finish that is not suitable for exposed architectural applications. It is designed to be concealed — behind drywall, above ceilings, or in areas where aesthetics do not matter.
What Is Intumescent Fireproofing?
Intumescent fireproofing is a thin-film reactive coating that looks and feels like paint at ambient temperatures. The dry film thickness (DFT) varies by fire rating and steel section — from around 40 mils for a 1-hour rating on heavy columns to 150+ mils for higher ratings on lighter sections. When exposed to heat above approximately 400 degrees Fahrenheit, the coating undergoes a chemical reaction and expands 20 to 50 times its original thickness, forming a dense, insulating char layer that protects the steel beneath.
This expansion is what gives intumescent coatings their name — "intumescence" means to swell. The resulting char has extremely low thermal conductivity, which slows heat transfer to the steel in much the same way that the thick layer of SFRM does, but starting from a much thinner initial application.
The key advantage of intumescent coatings is aesthetics. Because the coating is thin and smooth, it allows the profile of the structural steel to remain visible. It can be topcoated in any color, giving architects the freedom to expose steel as a design element while still meeting fire code requirements. Products like SprayFilm WB3 are water-based and low-VOC, making them suitable for interior applications in occupied spaces.
The tradeoff is cost and application time. Intumescent coatings require surface preparation (primer coat), multiple application passes with drying time between each coat, and often a decorative topcoat. The material itself is significantly more expensive than SFRM. For these reasons, intumescent coatings are typically reserved for steel that will be architecturally exposed.
Side-by-Side Comparison
A quick reference for specifiers and GCs evaluating which fireproofing system fits each area of the project.
| Factor | SFRM | Intumescent |
|---|---|---|
| Appearance | Textured, rough finish | Smooth, paint-like finish |
| Thickness | 1/2" to 2"+ | 40-200+ mils DFT (varies by rating) |
| Fire Ratings | 1 to 4 hours | 1 to 4 hours |
| Relative Cost | $$ | $$$$ (3-5x more) |
| Best For | Concealed steel | Exposed / architectural steel |
| Application Method | Spray equipment | Spray or roller |
| Surface Prep | Minimal | Prime / paint required |
| Durability | Fragile if exposed to impact | Durable, impact-resistant |
| Recoating | Easy — direct re-spray | Requires surface prep |
| Drying Time | Hours | Multiple coats over days |
When to Use SFRM
SFRM is the default choice for the majority of structural steel in commercial construction. If the steel will not be visible to building occupants, SFRM is almost always the right answer. Here are the most common scenarios.
Steel behind drywall or above ceilings
The vast majority of structural steel in commercial buildings is concealed behind wall assemblies or above suspended ceiling grids. SFRM is the industry standard for these applications because the textured finish is never seen.
Budget-conscious projects
At roughly one-third to one-fifth the cost of intumescent coatings, SFRM delivers significant savings on large-scale projects. For a 200,000 square foot office building, the cost difference between all-SFRM and all-intumescent can easily reach six figures.
Higher fire ratings (3-4 hour)
When the building code requires 3-hour or 4-hour fire ratings on primary structural members — common in Type I-A high-rise construction — SFRM is typically the only practical option. Achieving these ratings with intumescent alone requires very thick multi-coat applications that drive cost even higher.
Parking garages and industrial buildings
Parking structures, warehouses, and industrial facilities rarely require an architectural finish on steel. SFRM provides the required fire protection at the lowest cost for these utilitarian building types.
Renovation and recoating work
When existing fireproofing has been damaged during construction or needs to be brought back to spec on an older building, SFRM patching and recoating is fast, straightforward, and inexpensive.
When to Use Intumescent Coatings
Intumescent coatings earn their premium when the steel is visible and the design intent calls for a clean, finished look. These are the scenarios where intumescent is the right specification.
Exposed steel in lobbies, atriums, and restaurants
When structural steel is a design feature — visible in double-height lobbies, open atriums, or restaurant dining rooms — intumescent coatings allow the steel profile to remain sharp and clean. The coating can be finished in any color to match the architectural palette.
Architectural steel features and exposed trusses
Exposed roof trusses, decorative steel bracing, and architecturally expressed moment frames all require a fireproofing solution that does not compromise the visual intent. Intumescent is the only option that preserves the steel's geometry.
Renovations where aesthetics matter
Adaptive reuse projects — converting warehouses, factories, or historic buildings into offices, retail, or residential — often expose existing steel as a design element. Intumescent coatings protect the steel while enhancing the industrial aesthetic.
LEED and green building projects
Water-based intumescent products like SprayFilm WB3 are low-VOC, contributing to indoor air quality credits under LEED and other green building rating systems. They can be applied in occupied or partially occupied spaces with minimal disruption.
Historic building renovations
When working in historically significant structures where preserving the original steel aesthetic is important, intumescent coatings provide fire protection without altering the building's character or adding bulk to ornamental steel elements.
Can You Use Both on the Same Project?
Yes — and this is one of the most common approaches on commercial projects. A dual-system strategy uses SFRM on concealed steel (the majority of the building) and intumescent coatings on select exposed areas. This optimizes both cost and aesthetics.
Consider a typical mixed-use building: the parking garage levels, mechanical rooms, and office floors above the ceiling line all receive SFRM at a fraction of the cost. Meanwhile, the ground-floor lobby with its exposed steel columns, the restaurant with its visible roof trusses, and the open-plan co-working space with its exposed deck all receive intumescent coatings for a clean, architectural finish.
Andrex Insulation regularly executes this dual-system approach. On the Colorado School of Mines project, for example, we installed intumescent coatings on the exposed interior steel while using SFRM in the parking structure and concealed areas. Having one subcontractor handle both systems simplifies coordination for the GC — one contract, one schedule, one point of contact for all fireproofing on the project.
Cost Considerations: The Real-World Math
The cost difference between SFRM and intumescent coatings is significant enough to materially impact project budgets, so it is worth understanding the economics before locking in a specification.
SFRM is the more affordable option by a wide margin. On a per square foot of steel-protected basis, intumescent coatings typically run 3 to 5 times the cost of SFRM. The premium comes from multiple factors: the raw material is more expensive, the application process requires more labor (multiple coats with dry time between each), surface preparation is more involved (prime coat, potential topcoat), and the overall timeline is longer.
However, cost is not always straightforward. When steel is exposed by design, the real comparison is not just SFRM versus intumescent — it is SFRM plus the cost of building soffits, ceilings, or enclosures to hide it versus intumescent on its own. In many cases, especially on projects with high ceilings or complex geometries, the intumescent option actually saves money compared to the fully-burdened cost of concealing SFRM.
The smartest approach is to work with your fireproofing contractor during pre-construction. An experienced contractor like Andrex will review the structural and architectural drawings, identify which areas are concealed versus exposed, and recommend the most cost-effective fireproofing strategy for each zone of the building. This plan review often surfaces opportunities to save money that are not obvious from the spec alone.
Quick Cost Rule of Thumb
Concealed steel: SFRM wins on cost every time. No contest.
Exposed steel: Compare intumescent cost against SFRM + concealment cost. Intumescent is often cheaper once you factor in soffits and drywall.
Mixed project: Use both systems. Let your fireproofing sub recommend the split.
Frequently Asked Questions
Which is better, SFRM or intumescent fireproofing?
Neither is universally better — they serve different purposes. SFRM is the most cost-effective option for concealed steel (behind drywall, above ceilings) and can achieve up to 4-hour fire ratings at a fraction of the cost of intumescent coatings. Intumescent is the right choice when structural steel is architecturally exposed and needs to look clean and finished. Most commercial projects use SFRM for the majority of the building and reserve intumescent for select exposed areas where aesthetics matter.
Can you use both SFRM and intumescent on the same project?
Yes — and this is extremely common on commercial projects. A dual-system approach uses SFRM on concealed steel (above ceilings, behind walls, in mechanical rooms) to control costs, and intumescent coatings on exposed steel in high-visibility areas like lobbies, atriums, and open-plan offices. Andrex regularly installs both systems on the same project, which simplifies coordination for the GC since one subcontractor handles all fireproofing.
Is intumescent fireproofing more expensive than SFRM?
Yes, significantly. Intumescent coatings typically cost 3 to 5 times more than SFRM per square foot of steel protected. The higher cost comes from the material itself (specialized reactive coatings), the multi-coat application process, longer dry times between coats, and the surface preparation required (prime coat, topcoat). However, when you factor in the cost of building soffits or ceilings to conceal SFRM on exposed steel, intumescent can actually be the more economical choice for architecturally exposed areas.
What fire rating can SFRM and intumescent each achieve?
SFRM can achieve 1-hour, 2-hour, 3-hour, and 4-hour fire resistance ratings, making it suitable for even the most demanding high-rise and institutional building requirements. Intumescent coatings can achieve 1-hour to 4-hour fire ratings — products like SprayFilm WB3 are UL-listed for up to 4 hours. The required rating depends on the building's construction type and occupancy classification per the International Building Code (IBC). Your structural engineer or code consultant specifies the required rating for each assembly.
Who decides which type of fireproofing to use?
The architect and structural engineer typically specify the fireproofing type in the construction documents. The decision is based on the building's construction type, required fire ratings, and whether the steel will be exposed or concealed. However, an experienced fireproofing contractor like Andrex can review the plans during pre-construction and recommend where a dual-system approach might save money or improve the finished product. We regularly consult with design teams and GCs on the most effective fireproofing strategy.
Does Andrex install both SFRM and intumescent fireproofing?
Yes. Andrex Insulation has been installing both spray-applied fireproofing (SFRM) and intumescent coatings for over 38 years. Our crews are certified Cafco applicators for SFRM products like BlazeShield II, and we are experienced with intumescent products including SprayFilm WB3. Having one subcontractor handle both systems simplifies scheduling, reduces coordination overhead, and ensures consistent quality across the entire project.
Need Help Choosing the Right Fireproofing System?
Andrex Insulation has been installing both SFRM and intumescent coatings for over 38 years. Send us your plans and we will recommend the most effective fireproofing strategy for your project — optimized for cost, aesthetics, and code compliance.