*This article is based on publicly available data and legal information as of December 2025.

1. Building "ID" and "medical records": The cost of lost records

First, to understand the essence of the problem we are facing, we need to clarify what these two documents specifically mean in the professional fields of construction and real estate transactions. Many owners and prospective buyers have a fatal misconception that "it must be okay because there is a confirmation certificate."

The crucial difference between a "Confirmed Certificate" and an "Inspected Certificate"

The process of building a building involves strict checkpoints set up by the government and designated inspection agencies, and confusing these is like trying to leave a country without a passport.

First document: Building confirmation certificate (Kakuninzumisho)
This is a document issued before construction begins. It is a sort of "planning permit" that acknowledges that "the plans to be built comply with the laws and regulations on the drawings." However, this is merely a "plan." At this point, there is no guarantee that the building will actually be built exactly as planned.

Second document: Inspection certificate (Kensazumisho)
This is the most important document in this case. After the construction is completed, a final inspection is conducted and it is issued after on-site confirmation that the completed building has been built according to the plans and in accordance with the law. It is a "certificate of completion," so to speak. In real estate transactions, loans, and future extensions and renovations, the presence or absence of this document is the only legal basis for determining whether a building is "legal" or "illegal."

Third document: As-Built Drawings
Apart from legal documents, as-built drawings show the actual physical state of the building. Drawings at the design stage (final design drawings) are merely ideal images, and changes often occur on-site due to ground conditions and construction circumstances. As-built drawings are the "anatomy of the final building" that reflect all of these on-site changes.

The table below compares the difference in asset value between having and not having each document.

2. Historical Background: Why are there so many "houses without documents" in Japan?

First of all, why are so many buildings in modern Japan left without inspection certificates? To find the reason, we need to look back at the history of Japanese architecture after the war. This was not simply due to negligence, but was a structural problem born out of the demands of the times.

"Scrap and build" during the period of rapid economic growth

When the Building Standards Act was enacted in 1950, Japan was in the midst of a post-war reconstruction period. Providing a large number of homes to protect people from the elements, in other words, "quantity over quality," was the top priority of national policy.

Subsequently, with the introduction of new earthquake resistance standards in 1981, legal frameworks for building safety were put in place. However, in practice, the practice of "neglecting completion inspections" continued for a long time. Specifically, it is estimated that until the late 1990s, the national average completion inspection rate (the rate at which inspection certificates were issued) was only around 30% to 40%.

Behind this was a complex interplay of factors, including:

• ● Lending practices of financial institutions:
  In the past, banks accepted a "certificate of confirmation (permission before construction begins)" as a condition for granting a home loan, and did not require the submission of an "inspection certificate" after completion.
• ● Construction time reduction and site changes:
  Many builders chose not to undergo inspections because they did not want to be ordered to make corrections for minor changes made on site (such as misaligning windows or adding storage space).

The 2005 "Aneha Incident" Paradigm Shift

This sloppy management system underwent a dramatic change following the revelation in 2005 of the "Structural Calculation Document Falsification Problem (commonly known as the Aneha Incident)." This incident fundamentally shook the public's trust in architecture, and in response, the Building Standards Act was tightened in 2007. At the same time, financial institutions also strengthened their compliance, and changed course to a policy of not providing loans without an inspection certificate.

The graph below conceptually shows the trend in completion inspection rates. It shows that the situation changed dramatically after the turn of the millennium, but at the same time, it also highlights the fact that a large amount of "pre-date buildings" remain as stock.

3. Deviation from global standards: Comparison with Western "Home File" culture

Let's broaden our perspective and compare it with housing markets overseas. The reason why the used home market is so active in Europe and the US, especially in the US and the UK, is that information transparency is guaranteed.

The culture of "Home File" is deeply rooted in their society. This is a system in which documents such as new construction drawings, past repair records, equipment instruction manuals, and legal permits are managed as a single file or data, and handed over to the next owner when the property is sold.

Meanwhile, Japan's housing market has long been dominated by a "new construction supremacy" approach. The asset value of a wooden house is generally assessed as nearly zero (land value only) after 20 to 25 years of construction. This resignation that "the value will be zero anyway" is perhaps the biggest factor that has reduced the incentive to preserve documentation. As a result, vacant houses in Japan are treated like "used cars with unknown history," and are inevitably valued far below their true potential.

4. The reality of utilizing vacant houses: The turning point between benefits and risks

So, what practical impact does the presence or absence of documentation have when trying to utilize a vacant house? We will analyze this from the perspectives of both the "business promoting the project" and the "individual owner."

5. Regional Issues: "Records for Survival" in the Toyako Area of Hokkaido

The difficulty and risks of utilizing vacant homes vary greatly depending on the region. Hokkaido, which was the subject of this report, and particularly the area around Lake Toya, a famous tourist destination, are unique in that the presence or absence of documentation is directly linked not only to legal compliance but also to the physical viability and success or failure of the business.

1. "Invisible" insulation performance history

Hokkaido's housing technology has evolved in a unique way as it battles the harsh cold. Since the 1970s, construction methods such as block insulation and additional insulation have become widespread, but these cannot be seen from the outside.

Even for 40-year-old houses that look the same on the outside, the cost of heating oil in winter can vary by tens of thousands of yen per month depending on whether the insulation inside the walls is "50mm of glass wool, which was the standard at the time," or "100mm of high-performance urethane added at the owner's request." Furthermore, inadequate insulation construction directly leads to the risk of the structure rotting due to internal condensation.

If there are as-built drawings (plans and specifications), it is possible to estimate the performance (UA value) of the walls without removing them, and it becomes possible to accurately determine how much to spend on insulation renovations when planning a renovation. Without drawings, it becomes a gamble where you don't know until you open it up.

2. Roofs and solar panels in heavy snow areas

In recent years, with growing environmental awareness, there has been a movement to utilize vacant houses to install solar panels and turn them into ZEH (Net Zero Energy Houses).However, in areas with particularly heavy snowfall, including parts of Toyako Town, several tons of snow accumulate on the roofs.

In addition, detailed structural calculations are essential to support the weight of solar panels (approximately 15-20 kg/m²). If you have structural drawings, you can calculate whether the panels will support the roof without reinforcement based on the size and pitch of the rafters and the thickness of the beams. However, without drawings, you may need to take a safety factor into account and have to re-roof the entire roof or reinforce the beams, which can increase costs and cause the project to stall.

3. Tourism and Airbnb demand and fire safety issues

Lake Toya is an area with strong inbound tourism demand, and there is an extremely high demand for revitalizing vacant lakeside houses as "villas for rent" or "private lodgings." However, there are obstacles to overcome: the Inns and Hotels Act and the Fire Service Act.

In order to obtain a business license to operate as a lodging facility, the safety of the building must be proven. Particularly problematic are the presence of sunrooms or wooden decks that have been added on in the past without permission. If these are "illegal additions" that are not on the blueprints, or if there is no inspection certificate and legality cannot be proven, a business license will not be issued unless corrective work is carried out. The current situation is that there is no end to investors who purchase properties simply because they have a "good view," only to later realize this fact and be at a loss as to what to do.

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