A fire protection coating 10 includes insulation layer 20 including at least 20% free moisture. Insulation layer 20, preferably a vermiculite/gypsum mixture 26, is applied such as by spraying a water slurry of the mineral particles to structural member 85. Before the free moisture can evaporate, diffusion barrier 40, such as artificial stone formulation 44, is applied over the moist vermiculite/gypsum mixture 26. Moisture is retained within vermiculite/gypsum mixture 26 indefinitely and is released in the event of a fire to help cool and prolong the efficacy of fire protection coating 10.