Polyurethane coatings applied on PVC flooring substrate may influence its optical properties, especially gloss. Basically, rough surfaces look matte while smooth ones look glossy. However, the quantitative link between roughness and gloss remains insufficiently modelled. In this article, a microfacet-based model which predicts the BRDF from the 3D roughness slope distribution function f(dz/dx,dz/dy) is developed. Contrary to the different models existing in the literature, the computations are based directly on measured roughness from which the local slope distribution function is extracted. The model is applied to eight polyurethane coatings with different roughness and gloss. The results of the computations are compared to BRDF and gloss measurements. It is shown that this approach allows a good prediction of optical properties. In particular, the model predicts remarkably well the measured 60° gloss values.