A numerical method has been developed for the prediction of coupled heat and mass transfer and related processes in porous media exposed to elevated temperatures. The computer model predictions have been validated against experimental results of carbonate aggregate concrete slabs subjected to the ASTM E119 standard fire exposure. Output from the model depicts the coupled relationships between the temperature, moisture content, and pore pressure histories and distributions. This article investigates the numerical effect of grid spacing on the pore pressure fluctuations and the influence of the pore pressure on the spalling potential of concrete exposed to elevated temperatures.