In a conventional housing complex, additions or alterations carried out by the residents on their own initiative are rarely permitted. In Housing Corporation apartment buildings, they are prohibited by law. This is an administrative problem and has little to do with the flexibility of the structural system used in apartment buildings. Illegal extensions directly reflect the wishes of residents and it may conversely be argued that they provide a telling index of the shortcomings and planning defects of modern apartment houses. The questionnaire results suggest the possibility of autonomous improvement of the living environment constituted one of the principle factors which caused residents to describe Gunkanjima as a “good place to live” compared with Public Housing flats etc. It may be concluded that one of the reasons that Gunkanjima was regarded as a good place to live was that people were encouraged by the character of the space, the social institutions and attitudes of the community and even by the original structural framework of the buildings themselves, to adapt their environment to suit their own tastes and needs. In the course of our research we measured and recorded a considerable number of autonomous alterations and additions. There is not space to describe them at length here, so a limited number of examples must suffice to convey their character. (cf. Fig 2-7.8, Ph. 2-6) 1)Among the piloti close to the rock face in the Nikkyu flats, a semi-professional photographer had built a darkroom exclusively for his own use. 2)By enclosing part of a horizontally continuous veranda with sash windows, a sun room, or an extended living room with tatami mats was added to flats in Building No. 65. 3)In the Nikkyu flats (Building No. 20), the end of an open corridor had been enclosed with sash windows as an annex to the unfloored area of one of the flats. 4)There wee many examples where a home bar had been installed in the living room. When they wished to make an addition or alteration to a flat, residents were required to submit notice of their intentions to the Miner's Company-House Management committee and apply for permission. However, if they didn't give other's trouble, the company and neighbors were tolerant and didn't interfere. They could easily obtain building materials and tools among the odds and ends and surplus stocks which inevitably accumulated around a coal mine, and most of these autonomous alterations are said to have been done by the tenants themselves at very low cost.

As will be seen later, protective devices to shield apartments from typhoons or heavy seas were constructed everywhere both by the company and by the residents themselves. Besides autonomous extensions and alterations, damaged buildings were mended rapidly and without charge by the Building and Repairs Department of the company. In accordance with changes in the population of the island, the Building and Repairs Department often converted 2 apartments into one or vice versa. Especially in building No. 65 and in the Nikkyu flats, there were many cases of such conversions and a part of the piloti area was turned into an arcade of bars and restaurants, whilst a meeting hall and shopping arcade were constructed on the so called tidal defense floors. Despite its limited size, there existed on Gunkanjima a social system flexible enough to satisfy the resident's needs as far as possible given the circumstances. Moreover, it should be noted that the open trabeated structure of the buildings themselves contributed to this flexibility, making the space readily adaptable.

The buildings on Gunkanjima differ structurally from housing projects in a modern city in a number of ways.

1)They contained no solid structural walls between rooms, nor did they have a solid reinforced concrete structural core surrounding stair cases or lift shafts, Most large-scale prewar apartment buildings had a trabeated structure with external open stairs. Spatially, they were highly flexible.

2)Because the artificial ground was very well bonded to the bedrock it was easy to reconstruct passages, stairs and bridges. One of the reasons for this is that there were no internal stairs and external staircases were used for vertical circulation.

Then again, the reason why the veranda of building No. 65 had been reconstructed so many times was that in those days (Showa 20, 1945) the horizontal continuous cantilever had only just been introduced into Japan, and there were few apartment houses with balconies on every side. For the most part the frontage of individual flats in the apartment buildings on Gunkanjima corresponded to single structural bay, and only in the case of building No. 65 were there 2 flats in one structural bay. Incidentally, in the case of building No. 65, the width of the structural bay was 6.5m and its depth was 6m. Although the building was 10 stories high, one flat occupied the entire depth of one structural bay. As the story height was rather low, the beam arrangement which allowed them to fit 2 apartments into a single bay is considered to have been a rather revolutionary design.

The historical development of the buildings on Gunkanjima from the point of view of structural design, as outlined above produced flexible design which were readily adaptable to the needs of residents.

The difference between horizontal grouping concerned with the sense of unity of community above mentioned and vertical grouping of the type found in modern urban high rise housing projects was not simply a matter of psychological and physiological convenience. It was not just a question of finding the most efficient way of moving from one level to another in a multilevel complex; horizontal grouping was also closely related to the point set out below.

1)The formation and activation of semi-public space (making the open corridor function in the same way as a traditional tenement alley).

2)The use of the built environment to strengthen the sense of unity throughout the island.

3)The dissolution of the sense of alienation.

It is in the special qualities of the space and structure that we can find the reason that the inhabitants considered Gunkanjima a “good place to live”.