The lack of actual thermal properties of fire insulation materials lead to erroneous temperature prediction of protected structural steel members. For cementitious-based fire insulations, moisture held in the pores significantly alters the thermal response of the material. In this study, a heat transfer model is proposed to accurately predict the thermal response of cementitious-based fire insulations. The effects of the moisture and the decomposition of calcium hydroxide are incorporated in the thermal properties of the selected insulation material. The model was validated against the thermal response of the material obtained experimentally using the finite element programme abaqus (LAF Group, Sydney, NSW, Australia). Copyright © 2013 John Wiley & Sons, Ltd.