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The Potential of Small Wooden-Frame Building in Aging Japan

Faculty of Science and Technology, Keio University, Yokohama 223 8522, Japan
Eureka-Architectural Design and Engineering, Tokyo 171 0021, Japan
GROUP-Architectural Design Office, Tokyo 153 0042, Japan
INDA International Program in Design and Architecture, Faculty of Architecture, Chulalongkorn University, Bangkok 10330, Thailand
CO + RE, 623 Chok Chai 4, Lat Phrao, Bangkok 10230, Thailand
Author to whom correspondence should be addressed.
Sustainability 2023, 15(4), 3602;
Received: 11 October 2022 / Revised: 7 February 2023 / Accepted: 10 February 2023 / Published: 15 February 2023
(This article belongs to the Special Issue Sustainable Regeneration of Degraded Urban Structures and Fabric)


Wooden-frame structures, with the capacity for continuous renewal, are key resources for urban regeneration and so comprise one of the most sustainable construction methods. This was true in the past for Japan, but following World War II, wooden-frame structures were demolished and replaced at a rapid pace. However, today, with Japan’s aging and dwindling population, the growing number of abandoned houses has become a socio-economic issue. In response to this crisis, local initiatives have been established to address this problem. Some novel design and management practices have arisen to restore the value of excess wooden-framed buildings. The purpose of this paper is to discuss the current design and renovation practices of vacant wooden-frame buildings in Japan, as well as to evaluate these practices in light of a sustainable future, by approaching this issue from the perspective of architects and designers and investigating their roles in these processes. The paper starts with the evolution of this building type from the past to the present. Data from in-depth interviews with specialists in wooden-frame construction as well as architects who are involved in the renovation of postwar timber dwellings are gathered and discussed. The emphasis here is on the expertise these specialists and architects have in successful cases of design and space management, as well as the incorporation of those buildings into the local community. Our case studies are located in different urban contexts; a regional city, a peripheral area of Tokyo, and central Tokyo. The findings highlight the crucial role of architects who mediate between benefits and drawbacks of current rehabilitation efforts, which are nevertheless still outnumbered by abandoned houses. Nonetheless, these experiences are crucial and valuable for the long-term viability of this building type in Japan.

1. Introduction

Wood is one of the most sustainable materials for building when responsibly and sustainably sourced. It has both an economic and an aesthetic feature, meaning that the use of wood is widespread in all parts of the world [1]. Wood is a material with a high strength-to-weight ratio. Its light weight reduces mass, its ease of manufacturing and handling and its transportation so that it is, therefore, cost-effective. Wood also contributes to environmental comfort due to its low conductivity, high thermal inertia and natural hygroscopicity, it matches well with the current trends of eco-compatible and sustainable construction as it minimizes the environmental impact at all levels and is recyclable, renewable, biodegradable, and free of toxic contents [2]. In Japan, the abundance of domestic forests provides easy access to wood and has led to its widespread use. Beginning from a primitive roof structure used in ancient pit-dwelling houses, the construction of temples and shrines subsequently became popular as civilization and culture progressed. In relation to this, wooden joints and joinery that enabled detailed woodworking became widely used after the development of carpentry tools, along with the new availability of straight and soft wood species such as cypress and cedar [3]. In the world of traditional wood construction, the overall quality was supported by the unique skill of the craftspeople that were able to identify and process wood, leading to the development of structural styles and floor plans suited to the local climate, and from there resulting in the distinctive housing typologies adapted to each of the local contexts [4].
In the Edo period (between 1603 and 1867), population growth necessitated the mass construction of wooden houses. The current wooden-frame construction method evolved from this process. Improvements were implemented to further simplify the process, aiming to construct wooden houses that ensure maximum performance without advanced technology [3]. As a result, usable materials could be disassembled and reused for other buildings. These materials could also be sourced from collapsed houses. Even then, the lifespan of buildings was short, and for good reason [5]. Since then, the wooden-frame construction method, which originated from traditional building, has become more rational and economical due to population growth and higher demand for new housing. After the Meiji Era (between 1868 and 1912), the development of wooden buildings based on a Western structural system was introduced to Japan as a response to repeated earthquake damage [3].
Previously, it was an everyday scenario to observe housing reconstruction work in Japan, as there were many carpenters living in cities. It was common to modify the position of infills such as the walls, doors or windows of the wooden frame structure. In some cases, even the position of columns could be changed. In addition, the traces of such modifications were sometimes undetectable. This building system, which allows free addition and remodeling, is unique to lightweight timber construction. Furthermore, such modification could be carried out by referring to simple diagrams or sketches drawn by non-professionals. Due to this flexible system, it could be argued that the ease of this addition and reconstruction was taken for granted by the Japanese people [6].
Partial replacement can be carried out intermittently, allowing the wooden structure to be used semi-permanently. The simplicity of partial replacement also means that a building can be simultaneously modified, reused, and adapted. The wooden frame construction method is easy to rehabilitate, facilitating various modifications such as additions, reductions, and changes in room sizes.
In Japan, wooden buildings with easily replaceable components have been repaired and reconstructed by replacing damaged timbers, which extended the building’s lifespan. The wood was used and reused perpetually, proving the true sustainability of this practice.
However, since the end of the Second World War, when Japan was defeated and badly damaged, there was a reconstruction emergency. Here, the “faith in new construction” began, and it was believed that these new constructions were superior to the old ones, especially regarding residential buildings. This eventually became rooted deeply in modern Japanese culture so that living in a refurbished house was no longer a desired option. In Japan, the value of a building as a real estate asset is the highest immediately after its completion, and that value decreases over time [7]. Japanese homes gradually depreciate and become economically valueless within 20–25 years [8]. As a result, it is undeniable that the quality of housing deteriorated post-WWII and in the period of rapid economic growth during the process of mass housing production [9]. Therefore, the life expectancy of those buildings became extremely short. Even 60 years after the war, the average lifespan of these buildings was approximately 40 years [6]. In addition, Taro Igarashi, a Japanese architectural historian, reports that, while the average life expectancy of Japanese people is the best in the world, the average lifespan of housing is the shortest among developed countries—reconstruction is carried out in approximately 30-year cycles. He adds that the entire cityscape will be replaced within half a century [10].
The unsustainable cycle of modern Japanese wooden houses came hand in hand with a housing market trapped in anachronistic post-war social and administrative systems that included unsustainable housing loans, pricing and tax systems in real estate, and high inheritance taxes, which are not favorable for the owners of old houses. These combined forces provide a major incentive to demolish rather than improve houses before they reach their potential lifespan [11]. For these reasons, wooden architecture that residents could easily and freely customize has become a legacy of the past [12].
The fast pace of urban artefact replacement raises essential questions for both environmental and cultural sustainability. The embodied energy and memory in each building are lost due to its short lifespan, and the city loses its potential tangible cultural heritage in favor of growth in the construction (and demolition) industries [12]. Furthermore, Japan is aging and shrinking rapidly. These demographic crises have led to the increase in the number of vacant houses becoming an alarming issue in recent years.

2. Literature Review

2.1. The Problem of Vacant Houses in Japan

In 2018, the percentage of vacant houses reached an all-time high of 13.6%. Looking at the transition of vacant houses by types, the total number of such houses has doubled over the past 30 years; additionally, the percentage in the “other housing” type has been increasing at a greater rate—“Other housing” refers to vacant houses that are neither designed to enter the real-estate market (to be rented or sold) nor to be vacation homes. They are houses in which either the occupying household has been absent for an extended period of time, or houses that are scheduled to be demolished for reconstruction, which could lead to insufficient maintenance. Problems that may arise from the increasing number of vacant houses include the threat of collapse of the aging buildings and the deterioration of urban scenery and landscapes. These problems can reduce the ability to prevent crime and may therefore lead to an increase in delinquency [13].
Makiko Fujihira, a specialist in housing management and wood preservation, has recently remarked that the increase in vacant houses has become a nationwide problem. The aging of owners and their distance from the residence make it difficult for them to manage their buildings, leading to a rising level of concern about the progression of building damage. There are series of individual houses that are often privately owned, and in which daily maintenance and repairs are left to the owners. Additionally, these individual houses often stand in rows and are clustered together to form cityscapes and towns, so that they could be used as social positives in terms of their effect on the local environment [14].
The increased number of vacant houses also increases the risk of urban fires. Wooden buildings are susceptible to fire; in the Edo period, when a fire broke out, rather than using water to stop the fires, people would demolish the surrounding buildings to prevent the fire from spreading further and wait for the fire to extinguish by itself. In modern times, however, fire protection can be ensured by cladding the exterior of wooden structures with fire-resistant materials. Numerous old wooden houses are still in existence in Tokyo and, although they do not have adequate fireproofing, they can be retrofitted to improve their fire resistance. The revitalization of urban spaces through the renovation of wooden buildings is highly significant from the perspective of fire safety.
In other countries confronted with a similar problem, there are various types of actions attempting to address this issue [6]. In the U.S., “land banks” have been established as public non-profit organizations to acquire discarded houses, organize legal rights, and take necessary measures such as the demolition of the buildings or their preservation for further reuse. Similarly, “community land trusts” that acquire, manage, and operate both vacant houses and land to enhance local values have been established in various regions, and are currently playing important roles. In Germany, “Urban Conversion” and “Social Cities” aim to revitalize some specific areas in cases where there is a high concentration of unmanaged housing, or when there is a significant regional issue in using housing. In France, while emphasis has been placed on measures to return vacant houses to the market, “vacant house recycling” initiatives have recently been implemented in cities that face population decline, in which private operators and the government work together to revitalize vacant houses. In the U.K., in an area with a high percentage of vacant houses, a city purchased vacant houses and sold them for GBP 1 each (the buyers bear the cost of renovation), contributing to the urban renewal process. Following the example of the “1 pound housing project”, the “1 euro housing project” has been introduced in some areas in France. In South Korea, the “Small-Scale Housing Improvement Project” has been established to develop dense neighborhoods of aged and defective buildings.
In declining regions, the system of revitalizing an entire area rather than individual measures has emerged as a necessary strategy in many countries. In Japan, there are some examples which use the same initiative as land banks, though these are currently restricted to Tsuruoka city. This is quite limited compared with the role of land banks in the U.S. Each Japanese city faces the challenge of downsizing an overgrown city amid a declining population, which makes the revitalization of certain areas even more difficult due to a lack of economic vitality. However, this is an opportunity to change the conventional approach of urban development, which had favored growth, to a new approach tailored to shrinking cities.

2.2. Space Management through Renovation of Vacant Houses

In the Edo period, ownership and management were separate from usage—the landlord managed the buildings and facilities, and the shopkeeper moved in with a single chest of drawers. In general, people tended to pay significant attention to the durability of the physical environment such as the building and its architecture; however, to make the building usable and adapt to the changing needs of society, we need to consider the flexibility of the building management system [15]. It is a mistake to consider vacant houses and plots—which are considered to have no real estate value—useless and to suggest their elimination. This is because the vacant houses and lots that were abandoned by the real estate market and by the government have subsequently played a significant role in the development of various activities such as urban farming, children’s playgrounds, and centers for arts and culture. This was proven to be a success by residents who stood up to revitalize and reclaim the abandoned parts of their cities by their own hands [16].
To solve the issues related to the management of vacant houses, it is important not to leave them deserted but to manage them until they find stable use. To make this feasible, public support is necessary in addition to the management by the buildings’ owners. Considering these houses as local resources, mutual assistance by the local community is of utmost importance [17].
Yoneyama has reported that the root of the vacant housing problem lies in the fact that, in an era of declining population, finding an appropriate user (or tenant) for the previously used land or building is unlikely. Simultaneously, it is becoming increasingly difficult for an owner to sustain the occupation of their property responsibly [6], which indicates the necessity for the owner to consider other types of management systems. Thus, it is important to be concerned not only with the increasing number of vacant houses, but also the management system and institutional structure that support the revitalization of these houses.
Recently, in Japan, there has been an increase in efforts to activate the potential value hidden in the local community, such as the diverse use of available building stock through renovation and the revitalization of shopping districts and local industries. There is also a movement among the younger generation to proactively promote the history of urban districts and cherish the community. These emerging trends seek to add new value to residential areas beyond their comfort and the evaluation of their housing performance [14]. Among this group are architects who participate in community development and social bonding activities, reinforcing relationships with the nearby communities and incorporating activities which attract attention and are open to various local groups [18]. These activities are carried out via a series of small-scale, community-based projects, including the renovation of old buildings, the introduction of communal-use buildings in small units, and the creation and utilization of open spaces. The accumulation and spread of such projects have been developing into the regeneration of the physical and social environment in urban areas [19].
Regarding the benefit of renovating wooden buildings, including vacant wooden houses, Inoue has explained that there are three main benefits of renovation compared with new construction when viewed from the consumer’s perspective. First, it allows the consumers to modify the building to fit their own lifestyle. Second, it expands the possibilities of location selection. Third, it reduces cost. Renovation is not just about fixing buildings; as a method of urban regeneration, it is also expected to have social benefits [20]. Furthermore, during the period of population and economic growth, old buildings were constantly replaced by new ones; however, in the current era of abundant vacant housing stocks and declining birth rate, the former trend of scrap-and-build is no longer valid. In this context, “Renovation Urban Planning”, which reunites not only architects but also government agencies, is becoming a popular method of reutilizing the existing building stocks of vacant houses [21]. Therefore, renovation could be seen as a phenomenon that opens up the world of architecture, previously reserved for specialists, to the public. It is also expected to replace large-scale, government-led, top-down redevelopment projects with a bottom-up, small-capital-based approach to urban regeneration.

3. Research Methods

The aim of this paper is to further discuss the current design and renovation practices of vacant wooden-frame buildings in Japan and assess these practices in the context of a sustainable future, we approached this issue from the perspective of architects and designers and investigated their roles in the processes.
We focus on the sensibility of design thinking and the social involvement of the architect, which is crucial for revitalization, especially in the context of an aging and shrinking Japan. Our methods include the following:
Reflection from the perspective of a designer, comprising opinions from renowned Japanese architects known for their work with wood, and reflections from one of the author’s first-hand experiences in the design of wooden-frame buildings. This method helps to establish the importance of wood as the preferred material that expresses a deeply humane design quality and promotes engagement in the design process. Designers’ first-hand experience has posed questions that we further investigate in other design and renovation processes of abandoned wooden houses.
Interviewing specialists in wooden-frame buildings and the architects involved in the renovation process of postwar wooden houses. Our selection is based on their successful operation in different urban contexts: (1) a regional city, (2) a peripheral area of Tokyo, and (3) central Tokyo. This method allows us to understand those cases in detail in order to draw comparisons. We present these interviews in three case studies:
Nagaoka City, Nigata prefecture—Yasunori Tsumura
Sen-tsuku in Kita Senju, Tokyo—Kimitaka Aoki
Nishiike Valley in Nishiikebukuro, Tokyo—Tsuyoshi Sudoh

4. Reflection from the Perspective of a Designer of Wooden Frame Architecture

Many renowned Japanese architects have explored wood in their designs. One of the best examples is Kengo Kuma, who challenges the traditional methods of using wood in contemporary ways. His expression of wood comes in various styles such as the repetitive latices or “particlization” [22] and the multiply joineries (or Chidori). Even in large-scale architecture such as the Tokyo Olympic Stadium, the use of simple wood lumbers has been applied for sustainable reasons. The majority of Japanese architects who have experience in designing and renovating wooden architecture share a common feeling on the practicality and sensuality of this material. Commenting on wooden buildings and renovation practices, architect Masahiro Harada—one of the principal architects from the Mount Fuji Architect Studio, who has worked on a series of wooden architecture projects—states that the benefit of a wooden building lies in the fact that it is socially, spatially, and temporarily open-ended, creating a platform that connects people, and which facilitates maintenance and addition/renovation. He further explains that, theoretically, wooden buildings are never completed, or rather, have no end in time, which allows the residents to be constantly engaged in making. Furthermore, he disagrees with the recent trend of maintenance-free buildings and favors using local materials and craftsmen, while positively creating a structure in which local carpenters could constantly maintain the building. In doing so, local carpenters can continuously earn jobs, while making it easier for the residents to relate themselves to the construction process. This also involves constant engagement with local forests and mountains. Through these arguments, Harada positively evaluates the traditional practices around wooden housings and the customization conducted by residents [23].
The material properties of wood also contribute to these arguments. Wood has the property of “Softness”, which refers to the physical softness of the wood. The Japanese cedar, cypress, and pine trees often used for construction are soft. The specific gravity of Japanese cedar is 0.38, while concrete is 2.35 and steel is 7.87. Japanese cedar can easily be cut with a saw by laypersons, and another piece of wood can be inserted through a punctured hole or combined with maximum freedom and flexibility. No other building structure offers such freedom. It is also extremely easy to install additional items, such as shelves attached to a pillar, allowing residents to freely customize a building according to their preferences. Therefore, wood is easy to extend and remodel. Japanese architecture has a short lifespan, but even within that short period of time, it is extremely difficult to find a house that has never been extended or remodeled [24,25]. As previously mentioned, due to the composition of the wooden structure, the renovation of vacant wooden houses by these architects is highly compatible with the practice of urban area management and adapts to the context over time.
One of the authors of this paper has been engaged in both the design of, and research into, wooden-frame architecture [26,27]. The following two examples are referential cases which trigger some important issues related to the role of architects beyond spatial design.
Kankyu-tei (completed in 2012) is a small, detached room added to a wooden modernist house which was originally designed by Tsutomu Ikuta and built in 1964. It consists of an open-plan structure that looks like a simple roof added over one part of the garden. (Figure 1) The project provides a small public space in a densely populated residential area that is being renovated by each generation through the repeated subdivision of land plots and a high amount of reconstruction. The design includes an open wooden structure facing the living room of the existing house across the outdoor space, creating a livable space which integrates interior and exterior. The space is used as a salon to honor the husband, who was a poet, and his contemporaries, while simultaneously being used as a space open to local communities [28,29].
Dragon court village (completed in 2013) is a nine-unit housing complex built in a suburban residential area which is becoming increasingly car-centric. The design intends to extend the residents’ lives into exterior space. The wooden frame structure supporting the three-dimensional housing complex creates an opportunity for the residents to connect with outdoor space, while allowing them to adjust the exterior living environment under the eaves by themselves. (Figure 2) Several small, detached rooms for receiving visitors are located on the ground floor, which are both open to the exterior and interchangeable [30,31,32].
These are not examples of vacant wooden house renovations, but of the design of open spaces framed by wooden elements that have flexible use and welcome the public. They are residential projects that connect with the community. Wooden material creates a warm ambiance, while the smallness of the open spaces creates intimacy.
The designer provided several remarks on their experience by reflecting upon these two projects. The first remark involves the role of the architect beyond design. How can an architect continue to be involved in the local community and the project after completion? What kind of long-term strategies are necessary for the project to be accepted and loved by the residents and local people? The second remark involves methods of the implementation of those strategies. For a building and its common outdoor space to be utilized by various users and the local community, it is necessary to implement a “sustainable strategy for utilization” that allows for the flexible usage of space through deregulation. Because, in the Dragon Court Village, the user actively discovers the flexibilities of the space without defined functions, so utilization of the space becomes more active, as the usage is discovered by the user thereafter. As a result, shared spaces may be created, or the entire area may become a common space. It can be said that the private space and the common space are not divided, but their functionality is continuous or mixed, and the rules and manners of the space are decided and utilized by the residents themselves [27]. These practices could only be implemented in mutual accordance between local government and private actors, in addition to the formal requirements of the building that provides the exterior–interior connection. It is, in other words, the process by which a system for operating and maintaining the space is formed within the community. Finding the conditions for the local formation of a system to operate and maintain a space initiated by locals will be very useful from the practical perspective of space management, and is an important issue in implementing a new way of space management, including private management [33].
In the context of an aging and shrinking Japan, in which there are rising numbers of vacant houses and declining neighborhoods, architects face significant challenges. Vacant houses could become valuable assets for the local community. In this paper we explore how an architect can be involved in this process and what roles the architect may have beyond the design of a building. How can an architect continue to be engaged in the local community and the renovation project after completion? What kind of long-term strategies are necessary for the project to be accepted and loved by the residents and local people?
Furthermore, what are the methods for implementing these strategies. For a building and its common outdoor space to be utilized by various users and the local community, it is necessary to implement a “sustainable strategy for utilization” that allows for the flexible usage of space through deregulation. These practices could only be implemented in mutual accordance with local government and private actors, in addition to the formal requirements of the building that provides the exterior–interior connection.
In recent years, there have been cases where architects became actively involved with the local community by establishing their base within that community and simultaneously taking advantage of vacant buildings.
Based on these reflections from the above practice and research, we explored further issues and the future potential of vacant wooden-frame architecture by conducting interviews with three practitioners in this field. The main question is as follows: How can the architect manage the abovementioned issues that emerged from preliminary studies, i.e., “Flexibility of Wooden Architecture”, “Vacant Houses”, and “Architect’s involvement with the building after the project completion”?

5. Interviewing Specialists in Wooden-Frame Building and the Architects Involved in the Renovation Process of Postwar Wooden Houses

We selected three cases by local architects with experience in designing and managing old wooden-frame buildings in different contents—a regional city, a peripheral area of Tokyo, and central Tokyo—focusing on the wooden-frame construction method that is most common in small-scale projects in Japan.

5.1. Case Study 1: Nagaoka City, Nigata Prefecture—A Regional City

Yasunori Tsumura, who is a renovation architect and Associate Professor at Nagaoka Institute of Design, Sustainable Design Department, is currently working on the activation of under-utilized real estate, this involves actions such as running workshops on wooden building renovation (Figure 3) in Nagaoka city, Niigata prefecture, researching vacant houses and historical buildings, and renovation/urban development.
Nagaoka city, which has the largest population among suburban cities in the Chuetsu region, is located in the mid-south area of Niigata prefecture. However, due to its aging society, real estate and buildings are not only under-used, but also uninherited, even near the train stations located in the center of the city. By identifying the current situation of renovation/urban development in Nagaoka city, we can explore the issues and prospects of many suburban cities that have similar problems.
In Nagaoka city, the city center has been under redevelopment since the 2010s. This is due to the “Urban renewal and improvement plan (established in 2006)”, which intends to (a) recover the urban functions that are dispersed into the suburbs from the vacant areas of the city center, and (b) to create a city center that has high levels of accessibility and resiliency. Public facilities, including: “Machinaka-Campus Nagaoka (2011)”, a base facility for learning and cultural exchange; the “Kiokumirai (2011)” Nagaoka Disaster Archive Center; the “Aore Nagaoka (2012)” city hall and plaza; and the “Tomoshia (2016)” social welfare center, have opened as a part of an office building redevelopment project. “Komehyappyou Place Miraie Nagaoka”, which serves as a base facility for regional regeneration, is also currently in progress [34].
While the city center is thriving, the under-used building stock (vacant spaces) are increasing in parallel, particularly around the areas that were not subjected to such significant redevelopment. We can observe the active use of spaces near the ground floor facing the main streets, for businesses such as restaurants, along with a rearrangement of the city center; however, the lack of tenants or residents on the floors above and below this new activity is becoming a chronic issue, with even the building owners struggling to develop a clear plan to change the situation [35].
Opportunities for renovating under-used spaces emerge from the sufficient pairing of real estate owners and users such as shop owners or residents—namely, the actors. However, in order to pair these parties, a renovation business operator with ability, talent and passion is crucial. As Tsumura states, the combination of these three parties is the starting point of renovation/urban development (Interview with Tsumura, “Utilization of pre-existing stock in the city center of Nagaoka city”) [36].

Discussion 1: Shortage of Active Players Who Connect Under-Used Spaces with Users

It is complicated to connect these three parties (owners, actors, and operators.) There are many examples of town development events intended to connect the three parties, but the events end up being transitory and do not lead to concrete developments thereafter. However, the reality is that locals (real estate owners) would rather have a transitory event. Many owners are not in financial trouble even if the buildings they own are vacant. These owners are often conservative and want nothing more than to enjoy urban development events with people. They do not want to change the current situation and do not seek drastic solutions for vacant buildings.
When a place becomes increasingly local, the connection with the residents who live in that area becomes significant. It is almost impossible for renovation/urban planning professionals to immediately start a business if they have no previous connection with the local area, even though they are highly experienced. However, members of the younger generation with a lot of talent and ambition tend to leave for the city center to find more interesting job opportunities. This dilemma is another issue which revolves around regional revitalization. Even in areas with successful regional revitalization there are many cases where the younger generations left for the city center but came back with more experience, benefitting their hometown. The problem of renovation/urban development in regional areas is the extreme shortage of enthusiastic players who could connect under-used spaces with potential users—both are present, but they do not find each other. In addition, it is difficult to invite such individuals from outside, since they need a human resource rooted in that specific region. The only solution is to nurture such individuals who have a strong connection with the region within that local area. Tsumura points out that since each town is unique, copying only the results of successful examples from other towns will most likely result in failure, so it is important to set a goal for the town’s development and focus on the process of achieving this goal rather than the result. Specifically, it is important to start small and grow, and since what one person can do is limited, it is important to gather the strengths of various people.
The following example is a case in which an architect who came from outside the local area successfully conducted urban area management by utilizing the vacant houses in the region. This could be a solution to the problems revealed in the case of Nagaoka city.

5.2. Case Study 2: “Sen-Tsuku” in Kita Senju—A Peripheral Area of Tokyo

Kimitaka Aoki is an architect and the founder of ARCO architects, simultaneously acting as a social entrepreneur rooted in the local area and as a coordinator/administrator of a vacant house reactivation project in Senju-district, Adachi-ward, Tokyo. He efficiently facilitates public–private cooperative projects by supporting management and planning each of the initiatives.
Aoki worked on urban development in Toride city, Ibaraki prefecture, prior to starting his practice in Kita-Senju. However, several major challenges remained in the case of Toride city. Activities began in Toride when a grant from the government was issued; however, because the people involved in urban development did not own any property themselves, when the grant period ended and the subsidy ran out, they left and their relationship with the land ended. To solve this problem, in Kita-Senju a community development fund was established so that mechanisms such as these can continue even if the players leave the area.
Here, the architect only renovates the vacant houses, but oversees the overall situation of “Sen-Tsuku” by controlling the system that supports vacant house projects. Aoki employed the three methods below to facilitate the utilization of vacant houses in the Kita-Senju area [37].
A: Establishment of a platform for public–private cooperation for vacant house utilization collaborating with Adachi ward and representing those involved in the vacant house utilization platform, the overall management, and the planning of various initiatives.
B: Operation and advertisement of properties that could serve as a role model for vacant house utilization/collaboration with property owners. This involves discovering vacant houses, encouraging joint investments on renovation budgets with property owners, management of the facilities, operating and branding certain facilities, and management through occupation.
C: Advertisement of the know-how and system construction that could lead to the sustainable development of vacant house utilization. This involves collaboration with local banks and real estate agents, the planning of publications that cover the methods on vacant house utilization and establishment of funds, and offering knowledge on vacant house utilization and an examination of the contents.
Since these methods concern the hardware and software aspects of architecture, particularly the management issue, we closely observed the second aspect—B. The management of “Sen-Tsuku”—the old private house complex facility—as the model case for vacant house utilization, involved the following four characteristics.
B-1—Base facility management and advertisement: “Sen-Tsuku” is a property that was realized after about 10 years of consultation on the utilization of vacant houses and was carried out through the vacant house utilization platform (Figure 4). “Sen-Tsuku” was jointly funded by the owner and Aoki and opened in February 2020 as an old private house complex facility in a small downtown business district. Each room in the old private house was occupied with different types of businesses (Figure 5). It was around this time that the vacant house utilization platform began functioning, which resulted in rising momentum for the utilization of vacant houses in the area. The property was managed directly by ARCO architects, and the process, renovation details, subsequent management methods, and events at the property have been widely publicized. The property has now grown into a model case for the utilization of vacant houses in the vicinity and activity is prospering.
B-2—“Sen-Tsuku” model: By keeping the rent for each room as low as possible, the team calculated the overall optimal solution for the balance between project costs and rent, co-financing, and rent price to the tenants, so that the local residents could continue their activities in the way they wanted. ARCO architects lease the property on a lump-sum basis and occupy the property while receiving the rent from the tenants in a sublease arrangement. Arco architects are responsible for the operation and maintenance of Sen-Tsuku. (Figure 6).
B-3—Multi-layered facility: Taking advantage of the relatively large size of the residence and the large number of rooms, the complex is designed to house multiple types of businesses. The common areas benefit from the existing building, while major renovations are carried out in order to improve the exterior walls, insulation, and earthquake resistance, as well as the interior of each room. Investment costs and rental fees are as low as possible, while renovations are carried out sequentially throughout the years of activity in “Sen-Tsuku”.
B-4—The design of “Vacant houses” to create community involvement: “Sen-Tsuku” is located in the center of the Senju district, away from the station. It focuses on activities that are close to the local people. Since it is a complex facility, there is an expansion of activities beyond the tenants, and the system is designed to facilitate such expansion beyond the building through people’s connections. In urban spaces where residential and commercial spaces are mixed, as the number of commercial stores increases, the challenge is to maintain the residential environment for existing residents and to create initiatives and mechanisms for residential and commercial coexistence [38]. While this is an example of the utilization of a single vacant house, by holding regularly scheduled events for the neighbors it takes a form that widely communicates the activities and processes that serve as a model for the community (Figure 7). It is possible to expand the search for further vacant houses through “Sen-Tsuku” that are mainly conducted by the Adachi ward and real estate agents (Interview with Aoki, quoted from “Area Design through a Series of Efforts to Promote the Utilization of Vacant Houses in the Senju Area”) [39].

Discussion 2: Space Management through Utilization of Vacant Wooden Houses

The abovementioned highlights only one aspect of Aoki’s urban area management in the Senju area. In this case, Aoki is precisely the kind of player who connects the two needed parties—the under-used property and the users—as is the case in Nagaoka city. Based on his experience in Toride, Aoki is aware of the problems that Nagaoka city and other governments face when utilizing vacant houses; thus, he attempted to systematize the process of vacant house utilization. A project is only successful when an architect has a client, but in Aoki’s case, he has become a client himself, creating a community hub through the renovation of vacant houses. Aoki’s motivation for creating the community hub was based on the experience of a failure in a project he was involved in in Toride city. In that project, management professionals were invited from outside the area. They had a lot of practical know-how, but after they were gone, management became impossible. In other words, the project was transitory and unsustainable. Aoki learned how important it was that local people actually undertake the management.
In addition, Aoki has established a “Machizukuri (community development) Fund” to support efforts to contribute to “community development” so that the wave of vacant house utilization that has spread in the area will not stop even after Aoki is no longer a player there. The fund provides three main contributions: (1) a reflection of the characteristics of the Senju area; (2) knowledge of vacant house utilization; and (3) mechanisms to promote the pairing of owners of vacant houses and those who wish to utilize them. In doing so, Aoki and his team have introduced a more precise and versatile system by creating a mechanism and method that can be transferred to other regions in urban areas.
Aoki has found one of the keys to utilizing vacant houses. However, what about the importance of wooden structures? Dealing with wood requires sensible design and skilled craftmanship. The architect plays a vital role in the design strategy of the renovation project, particularly in the transformation of wooden private houses for public/communal use. The quality of design is equally important to the management of the project. Both skills are required to make this genuinely sustainable.
The following example is of a wooden building renovation in the urban center by an architect who has been involved in multiple wooden building renovations. We would like to consider this in terms of hardware (wooden building) that contains software (utilization mechanism) which determines the ease (or difficulty) of handling wooden architecture.

5.3. Case Study 3: “Niishike Valley” in Nishi-Ikebukuro—Central Tokyo

Tsuyoshi Sudoh is a design architect and founder of an architectural office, Tsudou Design Studio. Through the design of various programs such as housing, shops, hotel facilities, and complex facilities, his office reimagines the framework of architecture itself. In addition to architectural planning, the studio also provides design and consulting services for work before and after architectural activities, such as programs, event planning, business/management plans and proposals.
Sudoh has been involved in a number of renovations of wooden buildings, and among these, “Niishike Valley”, presented in this paper, is of great value as a successful example of a wooden building renovation project in the city center. The site is located within walking distance of Ikebukuro station, which can be considered the center of Tokyo, and is surrounded by high-rise condominiums and a fast-changing, bustling downtown atmosphere. Given the location, it would be financially beneficial to build a high-rise condominium similar to the surrounding buildings. However, “Niishike Valley” provides a place of relaxation and interaction for local residents. By studying the current status of “Niishike Valley”, where common open spaces that are provided for the community are created by utilizing existing wooden buildings, we can identify the issues in the renovation of wooden buildings and the utilization of such building types.
The project is a small area development in its first phase in a neighborhood surrounded by one-story wooden houses, wooden apartments, and RC apartment buildings. The plan is to convert one of the wooden one-story houses into a café and event space for local residents to use, and to create a small plaza and walking path for the town (Figure 8).
The 70-year-old one-story wooden house, once occupied by the owner, was planned as the center of the community in this area within the first phase of the Niishike Valley project. The extension was planned as a cafe to create a visible relationship between the residents and the local community; the dirt floor (Doma) space was designed to be an extension of the eaves of the dwelling on the same level as the exterior. The Japanese-style room is a rental space that can be used by local residents for workshops, etc. The veranda, eaves, dirt floor, and pergola are arranged along a series of concentric circles around the Japanese-style room, creating a gradational connection from the interior to the garden, making the space accessible from the outside and allowing people to feel nature from the inside. It is also intended to be a place where people can feel nature in the city, connect with people in the city through the greenery, and experience nature as well as see it, with edible plants in the existing garden attracting butterflies and birds [40].
Above all, the architects imagined that this place, which the owner has preserved and nurtured since the Edo period, could be passed on as a richer place if they could provide opportunities for the local people to discover ways to use it themselves, instead of imposing on local people a specific way to use it.
The following are some of the design strategies that were incorporated to achieve this goal:
  • The dirt floor, which remains at the same level as the ground level outside, and the wooden sash, which can be opened wide, create a generous connection between inside and outside, allowing visitors to feel the rich greenery of Niishike Valley and the wind and nature in town (Figure 9).
  • A consistent view from the back of the house to the outside is formed by creating a series of layered spaces from the dirt floor to the Japanese-style room, from the Japanese-style room to the porch, from the porch to the garden, and from the garden to the passageway.
  • The boundary between the site and the pathway is also blurred by using sleepers extending from the site to the street, as well as a brick pavement, creating a place in the metropolis of Ikebukuro, where one might imagine having a picnic on the street in the city (Figure 10).
  • The use of materials such as sleepers, bricks, and other materials familiar to the earth nearby will be used on the ground, and the existing bricks and granite on the site will be re-used as flower beds. The use of material is also not bound to specific language.
  • The space between the buildings, which was originally a back space, has been redefined as a place where people can enjoy touring around the area by removing the fence, paving the space, and planting a greenery.
  • Thin steel frames were placed at the entrance to the cafe and the garden of the event space. These frames serve as pergolas for plants, posts for counters, gates to welcome customers, and areas to gently divide the garden from the eaves and paths.
  • Various devices were dispersed to discover small occurrences and the joy of touring around, such as identifying the blossoming trees or the lives of insects and animals.
Some examples are “the line of flow to the restrooms is painted silver to reflect light and make the back of the passageway slightly brighter”, “the fixed bench and movable bench are of the same design to blur the difference between inside and outside,” “unused electrical wires (such as Gaishi’s) hidden in the ceiling are left as they are”, and “the signage is designed to blend in with the town”, “The signage base is designed to blend in with the city by using a city block sign board, etc.”, “We hope that Niishike Valley will bring new richness to the life of this town through the joy of exploring and discovering little things” (interview with Sudoh and quoted from Tsudou Design Studio website [41]).

Discussion-3: Creation of New Space through the Reduction in Size of Wooden Buildings

Niishike Valley succeeds in creating a single consistent spatial experience by connecting various pre-existing elements—such as vegetation concealed by a fence wall, gardens or alley—through a reduction (partial demolition) in size of the existing structure. Sudoh, the architect of the project, reports that “in the current building code and law, it is difficult to plan an addition compared to reduction”. As he states, “Reduction (Partial demolition)” is now a valid option in the context of a wooden renovation project.
Japan’s population will continue to decline, and the number of vacant houses will, therefore, increase. However, general contractors and housebuilders in Japan continue to build new buildings every day despite this projection. A system in which the economy can only circulate through new construction will eventually reach its limit. The crux of this issue lies not only in the continued construction of new buildings, but also in the current inability to the buildings already present. As Sudoh says, “We are demolishing as much as we are building. How can we reconnect what we have while building something new”? This is an important issue in a city saturated with buildings. Thus, the “design methodology of demolition”, a paradoxical problem, is highly significant and further questions are warranted.
The challenge is to persuade the client financing the project. As they purchase a renovation by an architect, they expect to see a new space with new qualities. From the client’s perspective, it is hard to speculate about the image of the project when being informed that, “We are going to tear down some walls and fences and create a new, comfortable space”. In the case of Niishike Valley, where many buildings are partially demolished, Sudoh states that “When we first took down the fence walls, the owner’s perspective changed. We were able to share the experience of knowing how much the environment could change by just simply reducing the fence wall”. One of the benefits of a renovation project is that the architect can enhance the client’s understanding introducing them to the newly created space and processing the design in tandem. In addition, wooden structures are by far the easiest to tear down both partially and fully. The customizability of removing obsolete components and inserting new ones is difficult to achieve with RC or steel structures. The Japanese people of today rarely have the skills of the Edo period, such as the ability to draw plans and understand the dimensional system of a space, nor do the general public have the knowledge to handle wooden structures easily—furthermore, the number of the local carpenters and master builders is declining. Therefore, the simplicity of handling and the flexibility of wooden construction is being lost. However, there is no time to be pessimistic about the loss of the great Japanese culture. Times are changing, and, unlike the past, there is a huge surplus of housing available today. In other words, there is a large amount of excess floor area. In order to make use of this surplus stock, we should only keep the minimum necessary area of vacant wooden houses and demolish non-essential parts of it. The small, remaining structures should be reinforced, and the newly created exterior space should be used as a garden—or, if that is too much to handle for the owner, it should be offered as an open space for the town that can be used by the local community. This way, gardens created in each house would be connected point by point, in the future creating an urban network several times larger than Niishike Valley. By looking at the design of Niishike Valley, we may have discovered another possibility for wooden architecture.

6. Conclusions

This paper first discussed wooden architecture as a system of buildings that can be easily modified for reuse, and summarized the existing research in terms of an overview, the history, and the potential uses of wooden architecture. Furthermore, specific small wooden buildings built in Japan were presented as referential cases to identify the issues that have emerged from the practical experiences of their design, particularly the architect’s role beyond design.
Next, we conducted a literature survey and interviews with designers and researchers of wooden building renovation cases to understand their responses to the “variability of wooden buildings” and the “vacant house problem”, which have been questioned in previous studies, and to the “involvement of architects after completion” and “innovations for sustainable use” that emerged in the referential study. Regarding the literature review and the interviews, first, “Renovation Town Planning in Nagaoka City, Niigata Prefecture” by Yasunori Tsumura clarified the challenges and prospects for utilizing vacant houses. Next, “Space Management of ‘Sentsuku’ in Kita-Senju, Tokyo” by Kimitaka Aoki clarified the challenges and prospects of urban area management utilizing vacant houses. Finally, “Wooden Renovation ‘Niishike Valley’ in Nishi-Ikebukuro, Tokyo” by Tsuyoshi Sudoh clarified the challenges and prospects of renovating wooden-frame-structure buildings. From these findings, we summarized the challenges and prospects of the renovation of wooden buildings in the future, including an ever-increasing number of vacant houses.
The challenge that Tsumura faces in urban development renovation in regional areas is that, although there are users and under-used real estate, there is an overwhelming lack of players to connect the two. It is difficult to bring in players from outside the region while fulfilling the necessity of having people rooted in the region, and it is similarly challenging to adopt the methods of successful examples from other places. In any case, the only way to find a solution is to nurture players rooted in the area.
In contrast, Aoki is aware of the problems that Nagaoka city and other governments are facing and has attempted to systematize the use of vacant houses based on his own experience in Toride. Aoki himself is a player who connects under-used real estate and users, purchasing the under-used real estate and becoming the user of these properties himself. By having Aoki acting in all three roles, a prototype of a successful project was created; this model was then rooted in the local community through the establishment of a community development fund in cooperation with the local government. One of the issues here is whether the system can function in other regions. In order to confirm whether this system is transferable, the case requires more time to progress under close observation; this will, therefore, require continued research in the future.
Finally, we have summarized the issues and prospects for the hardware to support the completed software, namely, the renovation of, and care for, wooden buildings necessary for the wider vacant house usage. When we create a new space, we tend to imagine a space that will be created by adding something new. However, in Niishike Valley, Sudoh created a spatial experience by connecting elements that were already in place (plants hidden behind walls, gardens, alleys, etc.) by reducing the size of the building. In Sudoh ‘s words, “demolishing as much as building” was exactly the way to design a rich garden, path, and shared space for the local residents.
The three cases in this paper suggest the following. First, Nagaoka city, a regional city, is facing a problem—a significant lack of operators rooted in the local community. In Senju, a peripheral area of Tokyo, the sustainable area management system has been established with local architects acting as operators to solve the problem. In Nishi-Ikebukuro, a central Tokyo area, local architects were taking advantage of the wood-frame construction to demolish non-essential parts, thereby reducing the cost and increasing the value of the property. In summary, the local architects, acting as operators rooted in the local community, and in cooperation with the local government, have established an area management system to increase the value of the building and its area while reducing the surplus floor space of vacant houses. As Tsumura pointed out, what is done in big cities, including their peripheral areas, may not be directly applicable to regional cities, but Sudoh’s method of reducing surplus floor space has the potential to be implemented in regional cities as well. This is because the utilization of vacant houses has been focused on filling them with tenants. In other words, they may have thought that the only option was to renovate vacant houses to make them more attractive so that they could find tenants to fill them. However, if the value of vacant houses could be increased by reducing the surplus floor space, this would be a viable option. Reducing floor space in central Tokyo, where land prices are extremely high, is surprising, but it has been done successfully. Sudoh’s practice in Nishi-Ikebukuro shows that reducing floor space can create value that more than makes up for the lost floor space and that this is easily possible because of the characteristics of wooden frame construction used in most of vacant houses.
As Japan’s birthrate falls and the number of vacant houses rises, the concept of “de-signing for demolition” will gain prominence there. It may be confirmed when the time comes that wooden-framed buildings are the simplest to shrink in size. The potential of timber building becomes apparent when both “reduction” and “addition” are given equal weight.

Author Contributions

Conceptualization, S.S. and D.B.; methodology, S.S. and N.S.; writing—original draft preparation, N.S.; writing—review and editing, S.S.; supervision-editing, D.B.; project administration, S.S. and N.S. All authors have read and agreed to the published version of the manuscript.


KLL (Keio Leading-edge Laboratory of Science and Technology) Designated Research Projects; Keio University Academic Development Funds.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Informed consent was obtained from all the subjects involved in the study.

Data Availability Statement

Not applicable.


We would like to express gratitude to the interviewees, Yasunori Tsumura, Kimitaka Aoki and Tsuyoshi Sudoh (see Appendix A for an overview of interviewees). Our gratitude also goes to Takuomi Samejima, who helped us with English proofreading.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

Yasunori Tsumura/Researcher and Area manager (Interview Date: 19 July 2022)
Yasunori Tsumura is a restoration architect and associate professor at Nagaoka Institute of Design, Department of Architecture and Environmental Design. He is currently engaged in the practice of utilizing idle real estate through research on vacant houses and historical buildings, and renovation town planning activities, mainly in Nagaoka City, Niigata Prefecture. He has served as a researcher for the Detailed Survey of Modern Monuments and as an observer for the Hokuriku Machinaka Habitat Promotion Council. He is a member of several committees.
Kimitaka Aoki/Architect and Area manager (Interview Date: 19 July 2022)
Kimitaka Aoki is an architect who designs buildings at ARCO architects and is also a community-based social entrepreneur and coordinator in a project utilizing vacant houses in the Senju area of Adachi-ku, Tokyo. Aoki provides consistent support for the overall management and planning of various initiatives. By providing this support, the project is effectively promoted through public–private collaboration. Aoki has received major awards, including the 4th JOYO Business Award Encouragement Prize (2016), the Adachi Ward Vacant House Utilization Promotion Project Coordination Public Proposal Grand Prize (2017), the Real Estate Institute of Japan President Award (2021), and the Urban Housing Institute of Japan President Award (2021).
Tsuyoshi Sudoh/Architect (Interview Date: 25 July 2022)
Tsuyoshi Sudoh is an architect who works at Tsudou Design Studio. He rethinks the framework of architecture while designing various buildings, such as residences, stores, accommodations, and complex facilities. In addition to his designing work, he also provides design and consulting services before and after architectural activities, such as programs, planning, business plans, and management plans and proposals. He is currently a part-time lecturer at Nihon University. His wooden renovation works have been published in Shinkenchiku (the oldest architectural magazine in Japan, first published in 1925) and are highly acclaimed in Japan.


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Figure 1. Kankyu-tei. Exterior view of the detached room. Visual connection is provided towards the back yard (source: Eureka, photo by Hideki Ookura).
Figure 1. Kankyu-tei. Exterior view of the detached room. Visual connection is provided towards the back yard (source: Eureka, photo by Hideki Ookura).
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Figure 2. Dragon court village. The wooden frames create an opportunity for residents to connect to the exterior space (source: Eureka, photo by Hideki Ookura).
Figure 2. Dragon court village. The wooden frames create an opportunity for residents to connect to the exterior space (source: Eureka, photo by Hideki Ookura).
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Figure 3. Workshop on wooden building renovation in Nagaoka city as part of the activation of under-utilized building in Nagaoka city, by Yasunori Tsumura (source: Yasunori Tsumura).
Figure 3. Workshop on wooden building renovation in Nagaoka city as part of the activation of under-utilized building in Nagaoka city, by Yasunori Tsumura (source: Yasunori Tsumura).
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Figure 4. A renovation of a wooden housing built more than 60 years ago. Complex facility composed of restaurants, grocery store, cooking class and workshop (source: ARCO architects & co+labo, photo by Hideki Ookura).
Figure 4. A renovation of a wooden housing built more than 60 years ago. Complex facility composed of restaurants, grocery store, cooking class and workshop (source: ARCO architects & co+labo, photo by Hideki Ookura).
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Figure 5. Floor plans (red shows the main information on the renovated parts) (source: Kimitaka Aoki, texts by authors).
Figure 5. Floor plans (red shows the main information on the renovated parts) (source: Kimitaka Aoki, texts by authors).
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Figure 6. Business model of “Sen-Tsuku” (source: Kimitaka Aoki, texts by authors).
Figure 6. Business model of “Sen-Tsuku” (source: Kimitaka Aoki, texts by authors).
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Figure 7. Many neighbors participate in the regularly scheduled events (source: ARCO architects & co+labo, photo by Hideki Ookura).
Figure 7. Many neighbors participate in the regularly scheduled events (source: ARCO architects & co+labo, photo by Hideki Ookura).
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Figure 8. Ground floor plan (source: Tsudou Design Studio, redrawn by authors).
Figure 8. Ground floor plan (source: Tsudou Design Studio, redrawn by authors).
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Figure 9. The dirt floor space is made to be on the same level as the garden by demolishing the floor which was originally at the height of the pre-existing foundation (source: authors).
Figure 9. The dirt floor space is made to be on the same level as the garden by demolishing the floor which was originally at the height of the pre-existing foundation (source: authors).
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Figure 10. East exterior view. The garden is opened to the facing street by demolishing the pre-existing fence wall (source: authors).
Figure 10. East exterior view. The garden is opened to the facing street by demolishing the pre-existing fence wall (source: authors).
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Sano S, Saito N, Boontharm D. The Potential of Small Wooden-Frame Building in Aging Japan. Sustainability. 2023; 15(4):3602.

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Sano, Satoshi, Naoki Saito, and Davisi Boontharm. 2023. "The Potential of Small Wooden-Frame Building in Aging Japan" Sustainability 15, no. 4: 3602.

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