## 1 Introduction
Although the implementation of such inspections varies from one territory to another, the bases are the same in virtually every country [24]. In the case of Spain, a periodic visual technical inspection called the Building Technical Inspection (ITE--_Inspeccion Tecnica del Edificio_) is carried out by specialised technical personnel (architects and technical architects) who draw up a report on the state of conservation of the building's common elements, determining maintenance actions that should be completed as well as their degree of urgency, to ensure the safety of the building as well as its inhabitants. In this context, BIM technology can be a good tool for managing a building's entire life cycle [25] and especially its maintenance, with a view to extending its useful life [26; 27; 28]. However, the BIM has yet to develop specific methodologies for including in the digital model the damage and alterations detected and assessing the building's state of conservation. Maintenance information linked to the BIM model improves the quality and precision of the building's operating systems [29]. The information stored in a digital twin covers all parts of the building and serves to create the database needed for continuous maintenance [30; 31]. Proper upkeep will improve a building's performance and reduce repairs and respective maintenance costs [32]. The aim has thus been to achieve a'smart building' that integrates the building's main systems in a single model included in a common environment that allows information and functions to be shared among different agents in order to improve the building's operations. The creation of an accurate inventory of construction systems, materials and damage existing in the building, concentrated in a database linked to the three-dimensional model, allows that data to be processed and analysed in an agile manner when decisions must be made. In this context, the BIM methodology is an excellent tool for carrying out rehabilitation interventions meant to achieve a more efficient building [33]. The aim of this work is to structure and design a BIM dynamic model (a model in which information can be added and updated during the building's life cycle) to record all the useful information on the state of conservation of a residential building, to optimise its conservation and maintenance, in turn enabling agile and up-to-date viewing and extraction of information about its conservation [34]. An analysis of the traditional procedures served to identify their problems; the BIM methodology regarding a building's state of conservation (SCABIM) was therefore designed to streamline this process. The proposed methodology was applied and validated in a case study of a tall residential building in Spain. The results showed that in the traditional process for assessing the building's state of conservation, the information is not connected (original building plans [35; 36; 37], previous reports, energy certificates, etc., are in documents without any link), and the location of any damage analysed and/or repaired is not known. This hinders their accurate analysis. The reports generated do not depict the damage's severity; on some occasions, action is not taken with the necessary urgency and situations of risk arise. They present a snapshot of the building's state of conservation and do not monitor damage, its evolution and the building's state of conservation in general. The proposed SCABIM methodology, however, responds to the identified problems by using a digital twin of the studied building. The information is linked to a dynamic model with the locations of damage. That information is continually updated, providing a picture of the building's state of conservation. The diagnosis of damage could thus be adjusted and, depending on the urgency of intervention, proposals for action can be prioritised and optimised.