# Adaptability of Buildings: A Critical Review on the Concept Evolution
## Content Analysis
### Dimensions and Overlapping Concepts

Table 5: Adaptability dimensions and overlapping concepts. Still, a distinct relationship that is always present in mechanisms and models of application of adaptability can be spotted with the concepts of _Flexibility_ and _Durability_. **Flexibility:** The term \"flexibility\" is the one most confused with adaptability in the literature by far, as both frequently appear together [25; 40; 48]. However, there are multiple inconsistencies in scholars' distinction and identification of each of the concepts. For example, [PERSON] et al. [24] refer that adaptations are carried out by an outsider (e.g., the user or the designer), while flexibility implies internal changes to fit external ones. Conversely, other scholars such as [PERSON] and [PERSON] [29] think that adaptability copes with changing environments without external changes, while flexibility implies changes from external. For [PERSON] [42], adaptability is a response to both internal and external changes, while flexibility is a solution-oriented strategy that makes it limited to certain alternatives [42]. From another perspective, multiple studies consider that both concepts carry similar meanings as in [PERSON] et al. [1], others even use both terms interchangeably, particularly when it comes to practice. [PERSON] et al. [25] confirm that construction practitioners and professionals tend to use the two concepts as synonyms. Studies might also show a conflict in relevance to the speed of change, frequency, and magnitude between the two concepts. [PERSON] et al. [40] refer to flexibility changes as short-term, quicker, and of a relatively lower magnitude while they see that adaptability implies larger-scale changes of major magnitude over long-term periods. By this meaning, a building can be adaptable without being flexible and vice versa. As for [PERSON] and [PERSON] [27], adaptability is limited to users' changing physical needs as when they become older or lose mobility. The authors consider that the term flexibility refers to a wider range of interventions than those offered by adaptability. Still, the general perception of flexibility in the literature is a mean to achieve a certain level of adaptation. **Durability:** In most studies, the concept of durability is often associated with the concept of adaptability [2; 3; 4; 25; 49; 50] since in order to design structures that support multiple uses and loading scenarios, they should be sufficiently strong [49]. Changes in functions of a building often entail changes to the required design loads [2]. Therefore, structures should be designed to sustain the worst case scenario [4]. Many practitioners consider durability a key facet of adaptability since a combination of durable structures (long-life) with loose-fit space is a main way to achieve adaptability [25]. Similarly, other studies reflect on the concept of durability that aims at extending the useful lifetime of materials and technology in buildings as complimentary to adaptability [3] since it significantly influences the level of change by allowing a certain level of flexibility in the way spaces are used.