This communication describes a prototype project completed by a research team of the Universidad Carlos III de Madrid to build an integrated metadata registry (IMR) for historical engineering archives. This registry was developed as part of a project completed for the Ministerio de Fomento of Spain. The proposed solution offers a way to collect and aggregate metadata from a network of archives that hold historical fonds of civil engineering documents. To enable metadata aggregation and ensure metadata compatibility, the archives participating in the network are requested to share authority records encoded according to the definitive version of EAC-CPF and use descriptors from a set of thesauri published by the Spanish Ministry.