If Steel Doesn’t Burn, Why Fireproof?

Steel is a strong, essentially, a non-combustible material that can be made into many shapes and sizes and is relatively inexpensive. However, its high strength properties are easily lost under the heat from a fire. How steel behaves at between 75oF (ambient temperature) is vastly different at 2000oF – a temperature reached in a typical fire. Steel loses most of its strength and is highly susceptible to bending and deflection between 800oF and 1200oF. These characteristics have inspired building codes and insurance companies to require fire protection on structures made with steel. The chart below shows that steel will lose about 60% of its strength at approximately 1100oF.

Spray applied fireproofing (cementitious) works by keeping elevated temperatures away from the steel substrate by converting the water within the material to steam. Supplementing this process are a number of additional reactions that contribute to a time delay including: reflection (mostly fibrous materials), ablative action (for intumescent materials), absorption, self-combustion, and other endothermic reactions. For any of the above to work, however, the fire resistive material must remain an undisturbed, intact, monolithic layer.

Independent testing laboratories consider failure when the steel substrate reaches a specific temperature; many of us think failure is when the building comes crashing down. First responders need time to get in and do their job. Maintaining the building’s fire safety design & and specifically, the fireproofing is crucial.

If you notice damaged fireproofing on a walk thru, upon inspection or for any other reason, please see to it that it is repaired and brought back into compliance. If you have records that support what was originally applied, contact that material manufacturer for their patching recommendations. If you don’t know what was originally applied, and guessing should not be an option, check out Universal Fireproofing Patch. The way to go when you don’t know.