Indoor air pollution is caused predominantly by emission of primary pollutants from building materials or finishing materials. Recently, there has been increasing interest in the new secondary pollutants caused by chemical reaction of the primary pollutants. In this study, the pollutants emitted from poly(vinyl chloride) (PVC) flooring material were measured, and 2-ethyl-1-hexanol (2E1H) and volatile organic compounds (VOCs) emitted from composite building materials made of PVC flooring material used as a self-leveling flooring were measured to identify the mechanism of emission of 2E1H. The moisture sorption isotherm was measured with a Magnetic Suspension Balance to examine the moisture content of the self-leveling flooring material and its effect on emission of 2E1H. 2E1H was emitted from the PVC flooring material through hydrolysis or oxidation of di-2-ethylhexyl phthalate (DEHP). The composite building material including the self-leveling flooring material emitted more 2E1H through hydrolysis over time. It was determined that liquid prevails in the self-leveling flooring material when the water content is higher than 4% and vapor prevails when the water content is lower than 4%. The prevailing liquid in the flooring material contributes to the increased emission of 2E1H and the prevailing vapor in the material did not cause increase in emission of 2E1H. It is considered that control of water in the self-leveling flooring material or concrete slab is very important in order to inhibit emission of 2E1H through hydrolysis of DEHP on the floor.