Commercial Fireproofing: What Building Owners Need to Know

Steel is one of the strongest structural materials available — but it has a critical weakness. When exposed to fire, structural steel loses approximately 50% of its yield strength at 1,100°F. In a building fire, steel can reach that temperature in as little as 10 minutes without protection.

Fireproofing is the solution. Applied to structural steel members, fireproofing materials insulate the steel from heat, maintaining its load-bearing capacity long enough for occupants to evacuate and for firefighters to operate safely.

For building owners, developers, and general contractors, understanding fireproofing requirements — and what separates a quality installation from a substandard one — is essential.

Fireproofing doesn't prevent fire. It doesn't make steel non-combustible (steel already is). What it does is slow the rate at which steel heats up during a fire event.

The goal is to maintain the steel's structural integrity for a defined period — typically 1, 1.5, or 2 hours — as specified by the building code for that occupancy type and construction classification. This time allows:

• Occupants to evacuate safely
• Fire suppression systems to activate
• Firefighters to enter and operate
• The fire to be contained before structural collapse

Spray-applied fire-resistive material (SFRM) is the most common fireproofing product used in commercial construction. It's a cementitious or gypsum-based material mixed with water and sprayed directly onto structural steel.

Types of SFRM:

• Low-density SFRM: Lightweight, fast-applying, used in concealed locations (above ceilings, in mechanical spaces). Typical density: 15–22 pcf.
• Medium-density SFRM: More durable, used in semi-exposed locations. Typical density: 22–40 pcf.
• High-density SFRM: Hard, abrasion-resistant, used in exposed locations subject to physical contact. Typical density: 40+ pcf.

Intumescent fireproofing is a paint-like coating that expands dramatically when exposed to heat, forming an insulating char layer around the steel. It's used where aesthetics matter — exposed steel in lobbies, atriums, and architectural applications.

Intumescent coatings are more expensive than SFRM but allow the steel to remain visible while still meeting fire-resistance requirements.

Prefabricated fireproofing boards (calcium silicate, mineral fiber) and ceramic fiber blankets are used in specific applications where spray-applied products aren't practical — around mechanical equipment, in retrofit situations, or where wet spray would damage adjacent materials.

Fireproofing requirements are driven by:

1. Construction Type (IBC Chapter 6) The International Building Code classifies buildings into construction types (I-A, I-B, II-A, II-B, III-A, etc.) based on the fire resistance of structural elements. Type I-A requires the highest level of protection — 3-hour fire resistance for primary structural frames.

2. Occupancy Classification High-occupancy buildings (assembly, educational, healthcare) have more stringent requirements than low-occupancy industrial buildings.

3. Building Height and Area Taller buildings and larger floor plates require higher fire-resistance ratings because evacuation takes longer and fire suppression is more complex.

4. Local Amendments New York City, for example, has its own building code (NYC BC) with requirements that differ from the IBC in several areas. Projects in NYC must comply with NYC BC, not just the IBC.

Fireproofing is a special inspection item under IBC Section 1705. This means:

• A special inspector must be present during installation
• The inspector verifies product compliance with the approved submittal
• Thickness and density are measured and recorded
• Bond strength testing may be required
• All results are documented in a special inspection report submitted to the building department

This is not a self-certification process. The special inspector is an independent third party — not the fireproofing contractor.

• Substrate preparation: Steel must be clean, dry, and free of oil, paint, or other contaminants that would prevent adhesion
• Product identification: The installed product must match the approved submittal
• Thickness: Measured with a pin gauge at multiple locations per the inspection protocol
• Density: Core samples taken and weighed to verify density meets the UL listing
• Adhesion/cohesion: Bond strength tested per ASTM E736

Insufficient thickness. The required thickness is determined by the UL listing for the specific steel section, fire-resistance rating, and product used. Applying less than the required thickness — even by a fraction of an inch — can reduce the fire-resistance rating significantly.

Contaminated substrate. Fireproofing applied over oil, paint, or mill scale may not bond properly and can delaminate over time. Proper surface preparation is essential.

Wrong product for the exposure. Low-density SFRM in a location subject to physical contact or moisture will deteriorate. Product selection must match the exposure conditions.

Inadequate coverage. Complex steel connections — beam-column joints, diagonal bracing, moment connections — are difficult to spray and are frequently under-coated. These areas require careful attention and verification.

Damage during construction. Fireproofing is often applied before other trades finish their work. Mechanical, electrical, and plumbing contractors frequently damage fireproofing during their installations. Repairs must be made with the same product and to the same thickness as the original application.

Not every insulation contractor is qualified to perform commercial fireproofing. Look for:

• Experience with SFRM and intumescent products on projects of similar scope and complexity
• Familiarity with special inspection requirements and the documentation process
• Manufacturer certification for the products being installed
• References from general contractors on comparable projects
• Proper licensing in the state where the project is located

ApexSeal NY is a certified fireproofing contractor serving commercial, industrial, and institutional projects across New York, New Jersey, Connecticut, and Pennsylvania. Our crews are trained in SFRM and intumescent application, and we work directly with special inspectors to ensure every installation is documented and compliant. Learn more about our fireproofing service.

For projects that also require penetration sealing, read our guide on firestopping vs. fireblocking — the two passive fire protection systems that work alongside structural fireproofing.

Contact us to discuss your project — we're available for pre-bid meetings, submittal review, and project-specific questions.