The importance of weathering of building stone is becoming widely recognized, and there is a need in modern thin stone design (less than 2 inches) to be able to estimate their durability. Stone deterioration processes include a number of agents, including salts, air pollution, freeze-thaw and biodeterioration. While the weathering properties of dimension stone can be judged by the examination of buildings in which it has been used, this method cannot estimate the durability of a different stone, a stone from a different part of the same quarry, a stone from a new quarry, or if the stone is to be used under different environmental conditions. Data is presented in this paper to show a correlation can be determined between natural and accelerated weathering of building stones. Real timeline information has been obtained by comparing accelerated weathering test data with data that is obtained from naturally weathered stone specimens. An estimate can be made to assess the life expectancy of a building stone subjected to natural weathering by using the accelerated weathering test procedure described in this paper. Based on our studies, 12 to 16 freeze-thaw cycles of the test procedure can be considered approximately equal to one year of natural weathering in the Chicago area.