Name two critical design considerations when specifying cementitious spray-applied fireproofing on steel.

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In cementitious spray-applied fireproofing on steel, two main design considerations drive performance: meeting the required fire-resistance rating and ensuring the substrate is prepared correctly for application. The fire-rating requirement determines how thick and dense the coating must be, which cementitious mixes and spray parameters to use, so the coating actually preserves structural integrity for the specified duration during a fire. If the rating isn’t achieved, the steel may be underprotected and fail prematurely.

The substrate temperature and condition for application are equally crucial because the coating’s bond and cure depend on it. If the surface is too cold or too hot, damp, oily, dusty, or not properly prepared, adhesion and curing suffer, leading to voids, cracking, or delamination that compromise fire protection. Proper surface prep and applying within the manufacturer’s specified temperature range ensure the coating achieves its designed thickness and performance.

Cosmetic factors or installation logistics, while important for workability, do not determine the fire-performance outcome.