Building classes are assigned to OBM buildings as a function of their occupancy case and their location (i.e. the centroids of the buildings belong to a certain data unit associated with an aggregated exposure model and occupancy case).
They are narrowed down according to two rules:
- number of storeys (if available),
- details on commercial occupancy, if the occupancy falls within certain options.
If these two rules lead to an incompatibility, that is, if there are no possible building classes that comply with both rules, then the building is assigned all possible building classes associated with the data unit that the building belongs to. This can be deemed better than leaving the building without any assigned building classes as no damage or risk calculation can be run without building classes (i.e. some estimate of the building's vulnerability is better than no estimate and having to ignore the building).