How Does Cementitious Fireproofing Work?
Cementitious fireproofing works by insulating structural steel from heat, using a spray-applied, mill-mixed plaster thick enough to slow how quickly the steel absorbs heat during a fire. That delay keeps the steel below the temperature where it starts losing structural strength, buying time for occupants to evacuate and firefighters to respond. EcoStar Insulation, a spray foam insulation company that also provides commercial fireproofing across Toronto and the GTA, applies this system on structural steel in both new construction and existing buildings.
What the Material Is Made Of
Cementitious fireproofing is a mixture of cement-based binders, lightweight aggregates, and water, mixed on site and sprayed directly onto steel surfaces. Once cured, it forms a dense, textured layer that stays bonded to the steel it protects, whether that steel is exposed to view or concealed behind other building materials.
How It's Applied
The material is sprayed on using specialized equipment, applied in a series of passes until it reaches the thickness specified for the building's required fire-resistance rating. Thickness is not one-size-fits-all: a beam supporting a heavier load, or a structure that needs a longer rating, typically needs a thicker coat than a lighter, shorter-rated assembly. This is part of why an on-site assessment matters before application starts, rather than applying a standard thickness across an entire building.
How It Slows Heat Transfer
Once applied, cementitious fireproofing insulates the steel underneath it from the heat of a fire. Structural steel loses strength as its temperature rises, and the coating's job is to slow that temperature increase long enough for the assembly to hold its rated fire-resistance period, whether that's one hour, two hours, or longer depending on the building code requirement for that structure.
Where It's Typically Used
This system is commonly specified for structural steel on commercial fireproofing projects, including high-rises, malls, offices, and industrial facilities, particularly where the steel is concealed behind ceilings, walls, or other finishes and appearance isn't a factor. It's also used on multi-unit residential and institutional buildings, such as hospitals, schools, and government offices, where a longer fire-resistance rating is required by code because of the number of occupants and the complexity of evacuating them safely.
Inspection and Maintenance
Cementitious fireproofing needs little ongoing maintenance once it's properly installed and cured, but it isn't maintenance-free. Damage from renovations, water infiltration, or general building wear can expose the steel underneath, and any damaged sections should be repaired to keep the assembly's fire-resistance rating intact. Annual inspections are the most reliable way to catch this kind of damage before it becomes a compliance issue, particularly on older buildings where renovation work is more likely to have disturbed the original coating.
Get High-Quality Cementitious Fireproofing Application with EcoStar Insulation
If you manage a building with exposed or concealed structural steel and aren't sure whether it has adequate fireproofing, or if existing cementitious fireproofing has been damaged, the EcoStar Insulation team assesses the structure and explains what would typically be required. As a spray foam insulation company that also handles fireproofing assessments across the GTA, we can look at both the building envelope and the structural steel in the same visit.
