Digital building modelling faces issues related to inconsistent integration/interoperability, in particular for a BIM GIS convergence. A consistent data conversion approach should consider semantic and spatial geometric modelling, therefore potentially leading to a loss of spatial geometric information. This paper simplifies semantic solving, and concentrates on the accuracy of the spatial geometric representation to avoid conflicting 3D spatial mismatches. To solve the geometry, original spatial specifications in 3D described in the IFC data schema are considered for all objects present in the model. The method is explored with a main BIM-IFC model, and additionally tested with two other models.