An Old Extension on a Japanese House: Build a Record of What Changed
The kitchen projects beyond the original wall, or a covered terrace now looks like a room. A change in shape is a reason to ask for a history, not enough information to declare the house compliant or defective. This guide proposes an evidence log for a buyer to share with the agent and appropriate professionals. The header is a schematic illustration, not a real property.
Describe the difference without diagnosing it
Save the advertisement and the plan you received, with their dates. Mark the area that appears different and ask whether it was added, enclosed or otherwise altered. Request the construction period and the name of any contractor the owner can identify. Write “owner says” beside an oral account; do not silently turn it into a verified construction record.
For a fictional example, a buyer notices that a rear room appears in photographs but not on an older plan. The next question is which drawing describes the current building and what records explain the difference. The photographs alone do not answer either question.
Ask for a coherent document packet
- Plans before and after the work, with dates and their stated purpose.
- Available applications, approvals, inspection documents and registration information relevant to the change.
- Contractor invoices, specifications, warranties and maintenance records, if retained.
- An explanation of missing records and who has already looked for them.
This is a request list, not a claim that every item is required or available for every alteration. Ask a local professional which documents matter for this building and intended transaction. Do not send the seller's personal information to unrelated third parties when sharing copies.
Keep three questions separate
First, what physically changed? Second, what records describe that work? Third, what does the change mean for your intended use or future work? A builder may help with physical conditions, while other records require the relevant specialist or authority. One reassuring answer should not close all three questions.
MLIT's consumer transaction guidance is a starting point for understanding the transaction and intermediary's role. Ask the agent to identify who will resolve each outstanding issue before you commit.
Make the inspection question specific
Ask the inspector whether the altered area is within scope, which junctions and accessible spaces can be examined, and what remains outside the inspection. MLIT's existing-home inspection framework describes qualified investigators; it is not a blanket certification of an individual extension.
Do not arrange destructive checks without permission. Record inaccessible areas explicitly. If you intend another alteration, request a separate feasibility review rather than assuming an existing extension makes yours possible.
Use a decision log
For each unresolved point, record the question, evidence received, reviewer, next action and decision deadline. “No document found” is a result, but not an automatic legal conclusion. Ask what uncertainty remains and whether it prevents your planned purchase or use.
Read the inspection-scope guide, then add this log to your house-viewing checklist. When you browse houses, keep a promising altered property pending until the relevant questions have an answer you understand.
Sources checked September 20, 2026. The log and fictional example are editorial tools, not legal or structural assessments.