To improve path loss estimation, a ray tracing method for inhomogeneous building surfaces and its verification are presented in this paper. Considering real building surfaces with many heterogeneous materials, the effective specular reflection based on a physical optics (PO) approximation is modeled and applied to the reflection in a ray tracing method. To verify the proposed method, measurement at 2.7 GHz is performed in a complex urban environment. Comparisons between the measurements and the ray tracing results are made in LOS and NLOS environments.