This paper discusses the semantic interoperability in the Construction sector, from the viewpoint of the FUNSIEC project. Shortly, FUNSIEC project aimed to answer the following question: is it feasible to establish semantic mappings amongst Semantic Resources (SRs) specifically created for the Construction sector? This quest has been answered positively through the development of the Open Semantic Infrastructure for the European Construction Sector (OSIECS). FUNSIEC work relied in a methodology that supported the development of the OSIECS triad, which is formed by the OSIECS Kernel, the OSIECS metamodel, and the OSIECS model. This paper presents the OSIECS triad, discussing the approach adopted, the challenges faced, the problems overcome, and the results achieved. The work to be done to continue this work is also discussed.