This research results from the development of a global inspection system based on previous studies about individual expert inspection systems for 12 types of elements/materials of the envelopes of current buildings. The research focuses on the rational harmonisation of the causes of defects in a global classification list, established from 12 individual lists. The process considers predetermined criteria, including guidelines for merging, splitting and combining causes to reach a comprehensive and simple list. The frequency of the prescription of causes of defects is analysed and the causes “C-D12 Dampening of the cladding system” in painted façades and “C-B7 Use of unprescribed, inadequate, incompatible, low-quality, non-certified and/or non-approved materials” in natural stone claddings stand out. Additionally, when analysing the relationship of causes with defects, some causes are highlighted because they are considered direct causes of defects in a broad range of building elements/materials, namely: “C-C9 Accidental collisions with the cladding”, “C-C7 Intentional collisions/vandalism”, “C-D2 Excessive, insufficient or differentiated solar radiation”, “C-D8 Presence of rainwater or snow” and “C-D12 Dampening of the cladding system”. The proposed list of causes successfully gathers causal knowledge on the pathology of the non-structural building envelope in a single component, homogenising the vocabulary used for several building elements/materials.