The modelling of historic monuments is a tedious task whatever the method employed. The complexity is of two kinds. The first comes from the architectural elements themselves (many types with varying shapes throughout the ages and according to the architectural styles). The second complexity is due to the number of architectural elements required to create a given monument. We have conceived and developed a parametric shape generator tool for virtual 3D reconstruction of cultural heritage monuments. Our method allows rapid modelling and accurate adjustments to the measured data. We also present the example of the vault study. The results obtained with the 3D model of Saint-Sauveur abbey in Figeac (France) are promising. The modelling time is greatly reduced in comparison with CAD, photogrammetry or laser scanning tools.