# Adaptability of Buildings: A Critical Review on the Concept Evolution
## Content Analysis
### Enablers and Promoting Models
#### 3.3.1 The Open Building
Architect [PERSON] implemented the incremental approach in his project in \"Quinta Monroy\" in Chile (Figure 4). He referred to the process he used as \"infrastructure as housing\" as he developed two-story half houses with free spaces left between them, allowing for future expansions to be performed by the residents according to specific guidelines [61]. Each half house formed a core of a home and contained all the basic and essential element and utilities that require professional involvement, such as supporting structure, stairs, bathroom, and kitchen installations. The remaining elements--partitions, interior finishes, and the remaining enclosure--were left for the families to add according to their means and needs. The idea of incomplete housing was advocated by several authors such as [PERSON] et al. [4], who encouraged the concept of a structural frame with free space to be customized by the user. Multiple studies built upon the open building concept to deliver strategies that facilitate adaptability of buildings, as it has been considered as the basis of adaptive design reuse strategies [58]. For example, a study conducted by [PERSON] [33] discusses that adaptability should be on both levels: infill and support. The author took the concept to a further level by allowing a flexible use of structural elements that contributes to extending the technical lifespan of a building. [PERSON] considers that a building structure should not disturb or limit infill change but rather facilitate it. He gives an example of movable columns on a certain grid, which would deliver a wider range of space layouts. Another solution addressing structural adaptability being a challenge against a building adaptations was introduced by [PERSON] et al. [62], who suggest a prefabricated modular system for apartment buildings. Figure 4: The incremental housing methodology in the Quinta Monroy project by architect [PERSON]. Still and all, the real-life application of open building has been limited to standalone housing projects, geographically based in Japan and the Netherlands [63]. The practical examples failed to incorporate an inherent flexibility as proposed by the approach [64]. This is probably because the approach's main focus was on the separation between long-life and short-life elements without paying a proper attention on the classification of element durability. [PERSON] et al. [57] justified this failure by arguing that the open building primarily focused on distinguishing decision power between each infill and support regardless the quality of materials and components. However, further regulations that promote the implementation of the concept were examined in Asia, including safety and durability enhancement of structures and provision of clear interior heights, which allow an increased flexibility for the infill system [59]. The open building approach remained as a philosophy as it fell short in delivering practical guidelines for designers to achieve an inherent adaptability. This is the reason why it remained inert for a while before rebounding later in the light of practical strategies that built upon its philosophy and complemented its insights with technical feasibility such as the Circular Economy in buildings.