Freezing damage in roof tiles is caused by a temperature drop In conjunction with a percent of saturation inside the tile. In order to understand the freezing-thawing process, it is necessary to know the moisture transport characteristics of a roof tile. In general, Japanese roof tiles have surface finishes. In this study, the water permeability of roof tiles with and without surface finishes was measured. The measured results showed that tiles with surface finishes had water resistances a few thousand-fold higher than tiles without surface finishes. Furthermore, it appears that the air entrapped within the tile has a significant influence on moisture transport In the tile. The influence of air was examined by numerical analysis, which demonstrated that an increase in the entrapped air pressure suppressed water infiltration. Copyright © 2009 by ASTM International.