This paper proposes an application of fuzzy logic to assess the quality of (semantic) mappings linking concepts from two Semantic Resources. The fuzzification process, i.e., the way of modelling fuzzy membership functions and assigning membership, is based on the definition of the concepts semantically mapped, as well as on the common semantics associated to those concepts, such as properties, equivalent terms and annotations. The work presented here extends the results achieved by the FUNSIEC project, which investigated the feasibility of creating an Open Semantic Infrastructure for the European Construction Sector (OSIECS). FUNSIEC produced a set of mappings amongst concepts from four semantic resources (e.g. IFC, ISO 12006-3, e-COGNOS, bcXML) currently available for the European Construction sector. We argue that semantic interoperability (at least in Construction) can be improved if we devise a way to measure the quality of the mappings. The challenges foreseen, conclusions and work to be done are also discussed here.