Frequently, algorithms for 3D facade reconstruction extract high resolution building geometry like windows, doors and protrusions from terrestrial LiDAR and image data. However, such a bottom-up modelling of facade structures is only feasible if the observed data meets considerable requirements on the amount of detail and coverage. For this reason, within our work, the explicit reconstruction of facades is enhanced by the integration of rules. The rules are derived automatically from already reconstructed facades, which serve as knowledge base for further processing. As an example, dominant or repetitive features and regularities as well as their hierarchical relationship are detected from the modelled facade elements. The rules together with the 3D representations of the modelled facade elements constitute a formal grammar. It holds all the information which is necessary to reconstruct facades in the style of the given building. In our approach, they are used for both the verification of the facade model generated during the data driven reconstruction process and the generation of synthetic facades for which no observed sensor data is available.