# Atlas of Defects within a Global Building Inspection System
## 1 Introduction
### Expeditious Tools to Assess Building Pathology  
Investigating building pathology is a complex process involving the observation of anomalous occurrences, deciding whether they are defects and determining their causes and origin. It may comprise elaborate discovery procedures, involving several in situ non-destructive and destructive diagnosis methods or even laboratory tests on collected samples. Focusing on the observation of building elements to detect defects, the inspection may be aided by some simple tools. Some of these, like binoculars or the zoom of a camera, help to get a closer look at building elements and decide whether a phenomenon is worth recording or just a temporary observation hindrance (e.g., an obstacle or the reflection from another building). Other tools provide basic data on building elements and detected defects, like a tape measure, which adds dimensional information to observations, or a spirit level, which immediately confirms the orthogonality of edges and surfaces. Additionally, portable and light comparison tools developed explicitly for inspection procedures are swift diagnosis methods that can be easily carried out in every inspection site and do not require advanced knowledge or a sophisticated apparatus [15]. Crack width rulers [16; 17; 18] and colour systems' samples [19; 20; 21] are two examples of such tools widely used, both using comparison as an operation principle. Using crack width rulers, the surveyor is provided with a small transparent rectangle with a set of printed lines ordered from thinnest to thickest [16]. Each line is identified by its thickness, allowing the easy determination of the width of a crack throughout its length. In other words, graphical data are complemented with quantitative data, providing a user-friendly instrument [17; 18]. Colour system's samples are a set of cards manufactured in a resistant paper and printed with solid colours in order to be compared with those of building elements observed on-site. Each solid colour is identified with a code according to the predetermined colour system, such as the natural colour system [19] or the Munsell colour system [20; 21]. The use of colour samples allows comparing (i) the observed colour with that of the beginning of the service life of the building element and (ii) the observed colour in different areas of a building element or building. Once more, graphical information, complemented with coded information, allows a more accurate diagnosis methodology. Additionally, standards EN ISO 4628-4:2016 [47] and EN ISO 4628-2:2016 [48] propose comparison methods to evaluate the degradation of paint and varnish coatings, namely the assessment of the degree of cracking and blistering, respectively. These standards provide pictorial criteria, allowing surveyors to match the visual characteristics of detected defects with those of the standard, referring to the size, quantity and density of cracking and blistering. In these situations, the assessment of coatings is also enhanced by the use of graphical information. The advantages of the mentioned easy-to-use, graphical and informative tools to aid inspection procedures raise interest in an analogous tool to help to observe defects and systematise their diagnosis. Such a tool, proposed in this study as an \"atlas of defects\", would be an image-based scale to ascertain the type of detected defect and assess its urgency of repair, complemented with essential written criteria difficult to express through photographs. Several scales are widely used in various fields of science, for instance, to measure [9] wind force (Beaufort scale), the intensity of tornadoes (Fujita-Pearson scale), hurricane winds (Saffir-Simpson