Toxic chemicals inside building materials must be detected early to prevent secondary damage because the chemical have long-term harmful effect on the human body. Although deep Raman spectroscopy is a potential candidate for inside harmful materials detection, it is very difficult to distinguish the Raman signal of the inside chemicals from the background signal of surrounding building materials. In this study, we developed wide-depth spatially offset Raman spectroscopy (W-SORS) coupled with a processing algorithm to identify inside chemicals. Furthermore, we proposed a method of measuring the thickness of an external building materials through signal processing of the W-SORS spectral slope.