# Adaptability of Buildings: A Critical Review on the Concept Evolution
## Content Analysis
### Enablers and Promoting Models
#### 3.3.1 The Open Building  
The \"Open Building\" approach is often assumed to be the underpinning foundation of the concept of Design for Adaptability (DfA) that holds a fundamental sense of flexibility [54]. The \"Open Building\" concept roots back to the 1960s when the post-WWII housing crisis was confronted with a movement to empower users. The escalating land values and scarcity of land in cities led to consideration of smaller and more efficient housing units inserted into multifamily residential buildings [55]. The idea behind the open building approach was first introduced by the Stichting Architecteen Research (SAR) and through prominent architects like [PERSON] in the 1960s. [PERSON] criticized in his book _Supports: An alternative to mass housing_[56] the state of uniformity that many of housing estates suffer from, pointing out the failure of architecture to meet the diversity of society, by imposing design decisions that occupants should have made themselves according to the timeline they define. The \"Open Building\" term implies a notion of simple structures that easily succumb to flexibility and change overtime [3]. Given that, [PERSON] suggested a separation between two building elements: the structural support \"Base building\" subjected to the investor decision, and the flexible infill \"fit-out\" that follows inhabitant's decision [57]. The \"Base building\" consisting of the fixed structure (e.g., structural pillars, beams, slabs) is usually considered the durable rigid part while the infill or \"fit-out\" (e.g., windows and doors, interior walls, furniture) is formed by the flexible parts that are exposed to recurrent changes [58; 33; 59]. Both durable and flexible systems are integrated with minimal interface problems, thus facilitating a building's adaptability to users' needs changing overtime [4; 59], for example, separating the envelope system from the structure by designing a specific interface allowing functional separation between those systems [3]. Spatial flexibility was among the primer drivers of the open building concept [55]. A prominent example in this regard is the Japanese traditional single family house that approached spatial flexibility by adopting rectangular plans for easy subdivision with moveable partitioning system of sliding interior panels and foldable partitions [55]. The interior spaces were divided to allow for a certain arrangement of \"tatami\" mats (floor coverings of standardized sizes) (Figure 3). At a later stage, the Japanese further contributed to the concept by creating distinct ownership patterns for each of the infill and support. The Japanese example is of a particular importance for showing the technical feasibility of the concept where huge efforts were implied, although met with modest success [26; 30]. However, the Japanese government released multiple regulations to promote the so-called skeleton-infill (SI) construction systems, perceiving their potential in prolonging the lifecycle of building and reducing waste generation [59]. Figure 3: An example of a Japanese traditional house. The Dutch experience is another example worth mentioning. Dutch architects were focused on social housing in the mid-20 th century as they divided plans into large multi-functional spaces of identical sizes. The spaces served as bedrooms at night, study spaces during the day for younger members of the family, and living areas in the evening [55]. The influence of social housing on the development of thoughts and strategies related to Open Building was a great deal as this strategy was used in the organization of informal settlements [60], providing affordable yet quality dwellings and controlling future expansions by residents. In the same context, another approach was also introduced by the incremental housing methodology, which is a flexible approach largely adopted in housing crisis and emergency architecture situations to ensure accessible and affordable solutions that at the same time guarantee users' satisfaction [61].