Termites in Japan: two enemies of timber
The shiroari (shiroari/シロアリ, literally "white ant", termite) is not an ant but a wood-eating insect that digests the cellulose in timber. In a country where the frame, the dodai (土台, sill plate on the foundation) and the hashira (柱, posts) are wooden, the structural risk is real — especially for the older properties foreign investors love. Two native species cause most of the damage, plus one imported invader.
| Species | Japanese name | Range | Threat level |
|---|---|---|---|
| Japanese subterranean termite | yamato shiroari (ヤマトシロアリ) | All of Japan except northern Hokkaidō | Most widespread; rises from the soil, seeks moisture |
| Formosan subterranean termite | ie shiroari (イエシロアリ) | Warm coasts: Kyūshū, Shikoku, Pacific side, Okinawa | Most destructive; huge colonies, reaches upper floors |
| American drywood termite | amerika kanzai shiroari (アメリカカンザイシロアリ) | Scattered urban pockets (imported) | Needs no soil contact: nests in roof timbers and furniture |
The key point: the yamato shiroari lives in the soil and climbs up through the foundation, which makes moisture and the crawl space decisive. The ie shiroari, confined to warm regions, builds massive nests and can colonise an entire building. These geographic differences should steer your vigilance by region — cross-reference our analysis of natural hazards before buying in Japan.
Spotting an infestation: the unmistakable signs
Termites work away from the light: by the time damage shows, the infestation is well established. Five clues should raise a flag during a viewing — the naiken (naiken, property viewing), which you can even run remotely using our video-viewing checklist:
- Mud tubes — gidō (蟻道, earthen galleries): ochre tubes along the foundation, the kiso (kiso, base) or walls, through which termites travel under cover.
- Hollow-sounding wood: tap the dodai, the posts and the bottom of door frames; a dull, hollow sound betrays timber eaten from within.
- Discarded wings: after swarming, identical translucent wings litter window sills and floors.
- Blistered paint, springy floors, sticking doors: signs of moisture and weakened wood.
- Frass: small piles of powdery wood, typical of the drywood termite.
The swarming season (gunpi): when everything shows
The gunpi (群飛, swarming) is the nuptial flight of future queens and kings. Seeing "flying ants" inside or right next to a property is the strongest warning sign. Its seasonality helps date an infestation:
| Species | Swarming period | Time of day |
|---|---|---|
| yamato shiroari | April–May (around Golden Week) | Daytime, on warm days after rain |
| ie shiroari | June–early July | Evening; drawn to lights |
| amerika kanzai shiroari | Summer (June–September) | Daytime |
Telling a termite from a carpenter ant: the termite has a straight waist, straight antennae and four wings of equal length; the ant has a pinched waist, elbowed antennae and unequal wings.
Before you buy: the termite inspection (shiroari kensa)
On an older house, the termite inspection drives the whole negotiation. Two complementary levels:
The specialist termite survey
An approved company runs a shiroari kensa (シロアリ検査, termite inspection): it checks the crawl space — yukashita (床下, under-floor) —, the kiso, the dodai, the attic and moisture levels. Many firms offer a free or low-cost survey to win the treatment quote.
The whole-house home inspection
The kizon jūtaku jōkyō chōsa (既存jūtaku状況調査, existing-home condition survey), Japan's version of the home inspection, covers structure, moisture and biological attack. Since the 2018 reform of the real-estate transaction law, the agency must inform you that such a survey is available — a right you should always exercise from abroad. Build it into your Japan property-buying checklist.
| Service | Indicative cost | What it covers |
|---|---|---|
| Simple termite survey | Free to ¥30,000 (€0–200) | Under-floor, foundation, active presence |
| Home inspection (kizon jūtaku jōkyō chōsa) | ¥50,000–80,000 (€330–530) | Structure, moisture, roof, termites |
| Add-on seismic assessment | From ~¥50,000 (€330) | Earthquake resistance of the frame |
For a long-empty akiya or a Kyoto machiya, always stack termite survey, moisture check and seismic assessment: those three items decide the real price. Cross them with our article on the 1981 seismic standard.
The legal framework: what the law requires on timber
Japan regulates the protection of new timber, but leaves older stock to the buyer's diligence.
- Mandatory treatment near the ground: the kenchiku kijun-hō shikō-rei (kenchiku kijun-hō施行令, enforcement order of the Building Standards Act) requires, for timber less than one metre from the ground (posts, sills, braces), anti-rot and anti-termite measures — the bōchō shori (防蟻処理, anti-termite treatment).
- Ten-year defect liability on new builds: the housing-quality law, hinkaku-hō (品確法), requires the builder to guarantee the structural parts of a new home for 10 years — but this does not apply to a second-hand purchase between individuals.
- Treatment lifespan: approved bōchō products lose their effect after about 5 years. Hence the golden rule: re-treat every 5 years, with a 5-year hoshō (保証, guarantee) issued by the company.
What the law does not cover — older homes sold privately — falls under the seller's liability for hidden defects (kashi tanpo) and the statutory jūyō jikō setsumei (jūyō jikō setsumei, explanation of important matters). Insist that the termite status and the date of the last treatment appear there in writing.
Treating and preventing: methods and costs
Two logics: prevention (a barrier before any attack) and curative treatment of an active infestation. Prices vary with the treated area — often quoted in tsubo (tsubo, ≈ 3.3 m²) — and the type of work.
| Method | Principle | Indicative cost |
|---|---|---|
| Chemical barrier (bōchō shori) | Spraying the soil and under-floor timber | ~¥1,320/m² (5-year guarantee); ~¥1,980/m² (10 years) |
| Prevention, 30-tsubo house | Full under-floor treatment | ¥100,000–150,000 (€670–1,000) |
| Curative treatment (active infestation) | Eradication + barrier | ¥100,000–300,000 (€670–2,000) |
| Baiting stations | Bait stations around the building | Annual subscription, no chemicals under the house |
| Drywood termite (spot treatment) | Targeted injection or fumigation | By quote, depending on spread |
Repairing the structure: the real cost centre
The chemical treatment is modest; it is repairing the damaged timber that hurts. Replacing an eaten dodai, reinforcing a kiso or rebuilding a frame can cost from several hundred thousand to several million yen. Build it firmly into your machiya or kominka renovation budget, and entrust it to trusted craftsmen and architects.
Worked example: a 40-year-old wooden akiya
Take a 40-year-old timber-framed house, 90 m² of living space (~27 tsubo), bought for ¥6M (≈ €40,000) in a Pacific-side prefecture — ie shiroari territory. The listing mentions no recent treatment.
| Item | Amount (¥) | € equivalent |
|---|---|---|
| Purchase price | 6,000,000 | 40,000 |
| Purchase costs (≤ 6%) | ≤ 360,000 | ≤ 2,400 |
| Home inspection + termite survey | 70,000 | 470 |
| Preventive under-floor treatment | 120,000 | 800 |
| Replacing a section of eaten dodai | 600,000 | 4,000 |
| Total termites + survey | 790,000 | 5,270 |
The ¥70,000 survey avoided a ¥600,000 nasty surprise: that is exactly its job. Depending on the findings, two strategies — negotiate the price down by the cost of the works, or walk away if the frame is too far gone. Run your net-yield assumptions through our yield simulator before you commit.
Common mistakes to avoid (and scams)
Missteps are expensive, and an entire market lives off the fear of termites. Stay methodical.
- Buying without an under-floor survey: mistake number one. A listing with no photo of the yukashita and no mention of treatment should lower the price, not raise your enthusiasm.
- Trusting the exterior alone: a repainted façade can hide a hollowed-out dodai. Always sound the low timber.
- Ignoring moisture: a poorly ventilated crawl space, blocked gutters, water-retaining ground — termites follow the damp. Treat the cause, not just the insect.
- Believing in a "lifetime" treatment: efficacy falls to ~5 years. With no re-treatment and no written hoshō, you are back to square one.
- Falling for pushy door-to-door sellers: the tenken shōhō (点検商法, "free inspection" sales pitch) is regularly flagged by the National Consumer Affairs Center of Japan (国民生活センター). Beware an "expert" who rings the bell, waves a chunk of rotten wood and demands an immediate signature.
Expert tips
Always ask for a company that belongs to the Nihon shiroari taisaku kyōkai (日本しろあり対策協会, Japan Termite Control Association), a written 5-year guarantee and two independent quotes. Keep the hoshōsho (保証書, guarantee certificate): it transfers and reassures buyers at resale. Finally, mind your home insurance: termite damage is generally not covered, which makes prevention all the more worthwhile.
Conclusion: shiroari is managed, not ignored
Termites should not put you off buying in Japan: it is a known, measurable, treatable risk. The right method is three-fold — survey before you sign, treat and re-treat every 5 years, and fix moisture at the source. A survey costing a few hundred euros protects an investment worth tens of thousands, and turns an old wooden house into a serene asset. To secure inspection, negotiation and works from A to Z, browse our hand-picked Akiyas, frame your project on the Projects page, and lean on our personalised support to buy in Japan with peace of mind.
Frequently asked questions
Should I have termites inspected before buying a house in Japan?
Yes, always for any timber property, especially an akiya or an older machiya. A crawl-space survey costs ¥0–30,000 (€0–200) and a full home inspection ¥50,000–80,000 (€330–530) — trivial against the cost of rebuilding a frame. Do it before you sign, so you can negotiate or walk away with full knowledge.
How much does termite treatment cost in Japan?
Budget around ¥1,320/m² for a chemical barrier with a 5-year guarantee, i.e. ¥100,000–150,000 (€670–1,000) for a 30-tsubo house. Curative treatment of an active infestation runs ¥100,000–300,000 (€670–2,000). Repairing damaged timber, however, can reach several million yen.
What termite species are found in Japan?
Three mainly: the yamato shiroari (Japanese subterranean termite), present almost everywhere; the ie shiroari (Formosan termite), more destructive, on the warm south-western and Pacific coasts; and the amerika kanzai shiroari (American drywood termite), imported, which nests in roof timbers without any soil contact.
When do termites swarm in Japan?
The yamato shiroari swarms in April–May, in daytime on warm days after rain; the ie shiroari in June–early July, in the evening, drawn to lights. Seeing "flying ants" at these times, inside or near a property, is the most reliable early warning of an infestation.
Is a termite treatment permanent?
No. Approved products lose their effect after about 5 years. The rule is to re-treat every 5 years and require a written 5-year hoshō guarantee. A seller who claims a "lifetime" treatment should make you cautious: always keep the certificate and the date of the last intervention.
Does Japanese law require termite protection?
Yes for new builds: the enforcement order of the Building Standards Act requires anti-rot and anti-termite treatment for timber less than one metre from the ground, and the hinkaku-hō law provides a 10-year structural guarantee on a new home. A second-hand purchase between individuals, however, is not covered — hence the importance of the survey.
Does home insurance cover termite damage?
Generally no: termite damage is treated as a maintenance defect and excluded from standard fire/home policies. That is precisely what makes prevention pay — it is better to re-treat every 5 years than to self-fund an uninsured structural repair.
Official sources
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