Termite damage (蟻害, gigai) is one of the most common hidden problems in an old wooden Japanese house, and a vacant akiya (空き家) is a likely place for it. Two species do most of the harm: yamato-shiroari (ヤマトシロアリ) and ie-shiroari (イエシロアリ). The main defence is a dedicated termite and under-floor inspection before you sign, because the standard government-defined home inspection is described around structural parts and rain intrusion, and the pages we checked do not list termites. This guide explains the species, where damage shows up, what to ask for, how treatment warranties work, and how termite findings connect to seller liability. We could not confirm a price list on official pages, so no cost figures are quoted. All sources are listed at the end (checked 2026-10-19).
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Get the free 12-point checklist Get a $49 risk reportYamato-shiroari and ie-shiroari are the two subterranean termites that matter most for buildings in Japan. The Japan Termite Control Association (日本しろあり対策協会) FAQ says Japan has 22 termite species but only a few damage buildings. It lists yamato-shiroari as found throughout Japan except northern Hokkaido, and ie-shiroari as found in warm coastal areas from Kanagawa Prefecture westward, part of Chiba, the Nansei (Ryukyu) Islands and the Ogasawara Islands.
| Point | Yamato-shiroari (ヤマトシロアリ) | Ie-shiroari (イエシロアリ) |
|---|---|---|
| Range | Nearly nationwide, except northern Hokkaido | Warm coastal areas from Kanagawa west, part of Chiba, Nansei and Ogasawara Islands |
| Nest | No distinct lump-shaped nest; the damaged wood or area is the nest | Large lump-shaped nests in buildings or soil; colonies of hundreds of thousands, up to about one million |
| Moisture | Prefers damp wood and soil | Carries water to dry wood, so dry timber can be attacked |
| Where damage appears | Mainly lower parts of the building, often together with wood decay | Can spread through the whole building; fast and severe |
The practical point: in an ie-shiroari region (warm coastal areas from Kanagawa westward, per the table), damage is not limited to the damp base, so roof framing and upper floors deserve attention too. In yamato-shiroari areas, the damp zones are the first place to look.
In an old wooden house, termite damage most often sits at the sill (土台, dodai), columns near the ground, the bathroom and entrance area, and the under-floor space (床下, yukashita), because these are damp and rarely seen. Because yamato-shiroari damage usually occurs together with wood decay, a leak and a termite problem often arrive as a pair.
A real-estate portal, athome, lists the common signs: repeated winged ants (羽アリ) indoors, sagging floors or pillars, a hollow sound when tapping walls, mud tubes (蟻道, gido) on foundations or around pipes, and spongy tatami. It also says yamato-shiroari swarm in April to May in the daytime and ie-shiroari in June to July at night, but it cites no primary source for those dates, so treat them as a rough guide.
The Shiga Prefecture page on the building condition survey (建物状況調査) describes visual and measured checks of cracks in foundations and exterior walls and of leaks, and MLIT's materials as summarised in our home inspection guide limit it to structural parts and rain-intrusion parts. Termites are not mentioned on the pages we checked. MLIT also says the survey does not determine whether defects exist. If you want termites covered, ask the inspector in writing.
The Japan Termite Control Association runs a termite and decay inspection system (蟻害・腐朽検査制度) for existing homes, started in 2002. Certified inspectors (蟻害・腐朽検査士) check for termites, decay, mold and humidity or ventilation problems, mainly by non-destructive methods such as looking, tapping and probing, plus moisture and humidity readings. The stages cover document review and an owner interview, then primary inspection of the exterior, interior, attic and under-floor areas, then a written report. Secondary inspections that may remove finishes are optional. Seller consent is typically needed for any inspection, and an akiya owner who lives far away may be slow to answer.
A past treatment may have expired, covered only part of the house, or been done by a company that no longer exists. The Association's FAQ lists exactly these situations (partial treatment, a defunct contractor, a bathroom-only job where no warranty was issued) among consumer questions. Ask for the warranty certificate and treatment map, not just a verbal statement that it was treated.
Termite control for an existing building is usually soil treatment, wood treatment, or a bait system. The Association's page on termite control calls soil treatment around the foundation the most effective way to stop entry, describes wood treatment as spraying or brushing chemicals on wood or injecting them into drilled holes, and describes the bait method as a closed system using about one-thousandth of the chemical of conventional methods. It adds that the Association's standard specification calls for re-treatment around every five years, which is why five-year warranties are common.
Where termites are active, anti-termite and anti-decay work should be done together, per the Association. If the damaged wood is structural, the repair also interacts with the building's age and design; see our guide on pre-1981 buildings and the old seismic standard.
We could not find an official, citable price list for termite inspection, treatment or repair, so no figures are given here. Costs depend on the size and structure of the building, the method, and above all on how much wood has been eaten, since replacing a sill or columns is a renovation job, not a spray job. The practical route is to get at least two written quotes that separate inspection, treatment and wood repair. For the wider renovation picture, see akiya renovation cost estimates.
It depends on the contract and the facts, and this is where a lawyer or licensed agent should read the document. Under Japan's Civil Code, nonconformity liability (契約不適合責任) lets a buyer notify the seller of a non-conformity within one year of learning of it. The All Japan Real Estate Association (全日本不動産協会) site quotes the rule and the exception: the time bar does not apply if the seller knew of the problem at delivery or was grossly negligent in not knowing.
Many used-house sales, especially between private individuals, are agreed on an as-is basis (現状有姿, genjo yushi) with seller liability limited or excluded in the contract. We could not confirm from an official source how common this is or how courts treat it, so do not assume you can claim later. If the seller or agent knew of termite damage, it should appear in the Important Matters Explanation; see our guides on the Important Matters Explanation and disclosure items in listings.
More general questions are in our agent question list.
Not necessarily. The official building condition survey is built around the main structural parts and the parts that keep rain out, and the pages we checked do not list termites. Ask the inspector in writing whether 蟻害 is in scope, or book a separate termite and decay inspection.
A five-year warranty is commonly mentioned, and the Japan Termite Control Association says its standard specification aims at re-treatment around every five years. Coverage differs by contractor, so read the warranty document itself, including which areas are excluded.
It depends on the contract and the facts. The Civil Code lets a buyer notify the seller of a non-conformity within one year of learning of it, but used-house contracts often limit or exclude seller liability, and a seller who knew about a problem is treated differently. Have a licensed professional read your contract before signing.
Two species matter most: yamato-shiroari, found almost nationwide, and ie-shiroari, found in warm coastal areas from Kanagawa westward. Ie-shiroari colonies are larger and can damage dry wood higher in the building.
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Get a $49 risk report Free 12-point checklistThis guide is general information based on public sources cited above. It is not legal, tax, or real-estate brokerage advice. Confirm every item for a specific property with the agent, the municipality, and licensed professionals.
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