According to ICOMOS Charter, the peculiarity of heritage structures requires the search for significant data and information of the construction, being the historical documentation one of the non-invasive main sources to understand the construction process and the interventions carried out to repair, rehabilitate and reconstruct the buildings. In Spain, since 1929, a reduced a group of architects were responsible of the inspection of the state of the monuments included in the National Artistic Treasure and, when needed, of drafting conservation, repair and consolidation projects, being these more than 14,000 conservation and restoration projects of cultural assets archived and preserved in the Spanish Cultural Heritage Institute’s Archive. After the introduction of democracy (1978), the country was organised into 17 Autonomous Communities with exclusive competence over historical, artistic, monumental, architectural, archaeological and scientific heritage. Since then, new regional archives have been founded, contributing to the dispersion of documentation and resulting in difficulties to find and locate the repair or rehabilitation technical reports. In this paper, the authors share their experience in the search, sources, location, access, and interpretation of the more than 20 intervention projects focused on the repair, reconstruction and rehabilitation of different structural elements in the school of Santo Domingo de Orihuela. The complex, declared an Asset of Cultural Interest in 1931, has been affected by floods and earthquakes, and therefore that, there are structural future implications to this research in terms of what should be a holistic conservation programme.