Tokyo and its 23 wards: minimum site areas

This map illustrates the repartition of the minimum site area in Tôkyô and its 23 wards (Little Tôkyô). According to many urban planners, developers and constructors, Tôkyô has a problem of scattered small-scale lots. This map does not represent the repartition of these small plots, but focuses on the minimum site area fixed at 60 m2 in residential areas, and 55 m2 in commercial areas.
For many constructors, Housing problems (lack of housing floor space, to quote one problem among many others) can be achieved by assembling the current small parcels. By doing so, high-rise and multi-used structures can be built in a large-scale parcel. Yet, assembling these micro-parcels poses various and important problems due to their size and their shape : many of them have irregular shape : hatazao, unagi no doko, kado, or respectively flagsite (L-shaped), 'eel' site (long and thin with a narrow entrance) and corner site (open to two sides. Therefore, one can add sloping (shamen) site to this list) are very hard to pool. The main characteristics are that their size is less than standard site area. In Tôkyô, as I wrote in the previous thread, standard site area is approx. 112.0 m2. However site area less than 100 m2 are very numerous.
Recently, due to a "come back" to the Center, many young people — young couple, single, couple with children, and even couple with children and one grand-parent — are searching to build a house on these small plots. These parcels are cheap insofar as the intensified subdivision practice (saibunka) causes to drop in value. As I wrote previously, the TMA and the National Territory Agency noted that a 270-square-meter site divided into 3 parcels of 90 m2 causes a important depreciation of the site. When the site value was 567 752 ¥/m2, each divided parcel (90 m2) costs 24 711 ¥/m2. In this context, the sale of such a small and depreciated plot is very hard, or used to be hard, for, recently, the new tendency demonstrates, as mentioned above, that they are sold much easier than the last decades.
And in this perspective, it would not be surprising that minikaihatsu (mini residential development plan) will continue to be used as main residential development tool.
Back to the site size: according to the Tôkyô Gouvernment Area, as it is mentioned on the illustration, 19 % of the minimum site areas of the UPA (shigaikakuiki) are compounded of smallest parcels. The minimum site area is fixed nearly 60 m2. Yet it is common to find plots less than 60 m2. Some housing projects such as Schemata Architects' 63.02°, a tiny house, with minimal footprint (the site floor is approx. 24.58 sqm). This House has been built in Nakano-ku, one of these densely wards of Tôkyô. This house is mixed-used: SOHO (very common in Japan) and apartment for rent. Due to strict regulation laws (that I will analyse briefly in a next, next, next thread, that means that will not be for now, not next week), particularly prospect rules (the relation to street and adjacent building), that is called in Japanese shasen seigen, the façade is inclined in 63.02° toward the front road. This inclination, also, permits to measure out light and ventilation inside the house, — an important point in Japan. Regulations law complies architects with a strict direct sunlight law (hikage kisei or nisshô kisei). As urban planner Yamagata Hiroo notes "Japanese residential units are required to have a minimum of four hours of direct sunlight every day". Indeed, the direct sunglight law fixes an alloted slot from 8:00 am to 4:00 pm. In the case of 63.02° SOHO/apartment, one will understand that, not only the inclination of the façade, but also the use of large windows that are opened on the inclined façade is important. I will probably go back to the analysis of windows in housing (of course the starting point will be Japanese Home due to this complexity), in a next thread.
Another important point is the plot itself. These subdivided plots are from many reasons that need pages and pages that this blog can't allow, but, it is prevalent to say that one of the utmost reasons is the nature and the character of these plots. They are the result of subdivision of fragmented farmlands. Indeed, the same Yamagata Hiroo assests that Tokyo "already has a problem of small parcels of farmland scattered within the built-up urban area." Japan, in fact, has a long tradition of fragmentation of farmlands. As I wrote in the previous thread, many reasons, that I won't explain in detail, play an important role. I will just enumerate them : Land readjustment (kukaku seiri), mini residential development plans (minikaihatsu), and of course land price speculation, and land tenure.
As you can see in this map, these tightest plots are concentrated in five wards: Setagaya, Megurô, Edogawa, Nakano and Suginami. Those wards have a high demographic density, respectively 148.3 inhabs/ha, 183.0 inhabs/ha, Edogawa 133.8 inhabs/ha, Nakano 201.6 inhabs/ha, 158.6 inhabs/ha, or are closed to the central wards such as Megurô (near Minato).
In order to control the subdivision of plots, TMA introduced measures of minimum site areas, that, as mentioned above, are fixed at 60 m2 for the residential areas and 55 m2 for the commercial areas. These measures were passed in the framework of the 1992 Urban Planning Act. Minimum site area fixed at nearly 60 m2 has, precisely, a coverage ratio of 60 %. Of course some areas are under stricter restrictions such as zones under natural disasters protection. I will post a thread illustrated with maps represented these zones under natural disaster zones (bosai in Japanese), such as the protection zones (bôka chiiki. The Earthquake Prevention Renewal Areas designated in Central Tokyo is one of these numerous protected districted).
TMA plans to create a subdivision manuals (saibunka shidô yôkô) that would permit to control the intensified subdivision of plots.These manuals would indicate various patterns such as division number, minimum site areas, lot coverage ratio, among others. Indeed, if residential developments based on land reajudment (kukaku seiri) and redevelopment projects (saikaihatsu) are under restriction, the control over mini residential development (minikaihatsu) practice is still very light. Indeed, as André Soressen notes, "In LR and redevelopment projects the formal agreement of all or a two-thirds majority of landowners is required by law", while no restriction as such had been passed in the Urban Planning Act of 1968. Then, developers using mini residential development instrument is not complied with the development of land for infrastructures and facilities. One of the goals of the Urban Planning Act of 1992 is to make up for this shortage and to halt subdivision damage.
A next thread will focus on some wards which are passed stricter controls on subdivided land.

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