Three species, and one that breaks the rules

Japan has over twenty termite species. Three do serious damage to houses, and the third behaves unlike the other two in every respect that matters.

Every assumption in the left-hand column is reversed in the right-hand one. That is the whole problem.

Why the standard treatment does not reach it

Japanese termite control works in two ways. Chemical treatment of the soil and timber beneath the house creates a barrier against insects coming up from the ground. Bait systems placed around the perimeter draw termites in and eliminate the colony through them.

Both are defensive lines drawn between the earth and the building. Both assume the termites come from below.

The drywood termite goes over the top. Winged adults fly and enter through eaves, vents, roof details and gaps around window frames. Nothing about that route passes near the treated soil. And because the insect survives on the small amount of moisture held in dry timber, it is at home on an upper floor or in a roof space where the native species could not live.

Its breeding habits finish the job. Rather than one large colony, it establishes many small ones dispersed through the timber. Eliminating one does nothing about the others in a different post, a different door frame, a different piece of furniture. There is no single nest to destroy, so the usual strategy has nothing to aim at.

The only sign is sand on the floor

This species eats the inside of timber and leaves the surface almost intact. Tapping produces a hollow note, but the wood can look entirely normal.

What gives it away is the droppings. Because the diet is dry timber, the droppings are dry too: hard grains resembling coarse sand, pushed out of small holes and landing directly beneath the damage.

• The same grains reappearing somewhere you have already cleaned
• On the sill of a traditional room, on tatami, inside a cupboard, under a window frame, beneath furniture
• Coloured close to the timber, from yellowish brown to near black

In a house where somebody lives, this gets noticed. It is odd enough to prompt a question.

In an empty house, nobody sweeps. The grains accumulate, and then somebody tidies once a year and clears them away without knowing what they were. Years later, at the point of selling or renovating, the structural timber turns out to be hollow. That is the typical way this is discovered, and by then the damage is done.

What the warranty actually says

Here is the part that costs people money.

A five-year termite warranty is commonly handed over with a secondhand house or after treatment. Standard treatment is built around soil-borne species, so the warranty is written around them too. Since the method does not structurally address the drywood termite, damage by that species is normally excluded.

That is not an inference. It is written in the documents.

Two ways of writing the same exclusion

Across the warranties we have examined, the exclusion appears in two forms. They are logically identical and they work on the reader completely differently.

The first names the species. One warranty stated, in red at the foot of the page, that cover applied to the two established species and did not extend to the drywood termite. It is named. It is in red. Anyone who reads the page understands the position.

The second lists what is covered and excludes the rest. Another set it out among the exclusions as damage caused by termites other than the two named species.

The meaning is the same. The effect is not, because the words "drywood termite" never appear anywhere on the document. A reader who does not already know that a third species exists passes straight over the line. They learn what it meant later, when an inspector stands in the room and identifies the insect.

Disputes come almost entirely from the second form.

For a buyer who cannot read Japanese, whether somebody translates that one sentence is the difference between an informed purchase and a very expensive surprise. Five things are worth establishing about any termite warranty:

1. Which species are covered, named explicitly
2. What the exclusions say
3. How long is left to run, and from what date
4. Whether it transfers to you as the new owner
5. Whether it covers re-treatment only, or repair of the damage as well

The other ways a warranty stops working

Species is not the only exclusion. Conditions of this kind commonly appear, though the wording varies between companies:

• Water ingress from a roof leak or plumbing failure
• Flooding beneath the floor from an earthquake, flood or tsunami
• Alteration or extension where the new work was not treated
• Damage to the foundation concrete, or timber and waste left in contact with the ground
• Treated soil that has been substantially moved or washed away
• Damage to furniture and other movable property
• Repairs carried out before the treatment company has inspected

Now apply that list to a house standing empty overseas. A roof leak develops, nobody sees it, and the subfloor gets wet. At that point the warranty may already have failed, before any termite has arrived. Neglect does not only degrade the building. It quietly cancels rights that exist on paper.

The final item deserves separate attention, because it is the one an overseas owner is most likely to trip over. Word arrives that there is a problem. You are thousands of kilometres away, so you ask a local builder to sort it out. That instruction alone can end the cover. The first call is to the company that did the treatment, not to a contractor. Knowing the order changes the outcome.

Where it is found

This risk is not uniform across Japan, and the location of the property changes it substantially.

The species was first confirmed in Japan in 1976, in a two-storey timber building in Edogawa, Tokyo, having arrived in imported timber and furniture. It has since been reported across a large number of prefectures, from the north of Honshu down to Okinawa. It is not established in Hokkaido, although rising insulation standards in Japanese houses have been noted as a reason that could change.

The important characteristic is that the distribution is patchy rather than general. Because the insect has spread mainly by being carried in timber and furniture rather than by flying, it turns up in concentrated pockets. Neighbouring towns can have completely different histories, and within a single municipality it can be confined to particular districts.

So "it is rare in Japan" and "it is all over Japan" are both wrong. The only useful question is what has been reported in the municipality where your property sits. The national association concerned with termite control publishes information on species and distribution, and that is the place to start.

One further point about timing. Colonies are typically established for several years before damage is discovered, because each nest holds relatively few individuals and progress is slow. A house you are looking at now can already have this underway with nobody yet aware of it.

Old houses and akiya are the higher risk

The properties that appeal most to overseas buyers are, unhelpfully, the ones most exposed.

• Exposed timber. Visible beams and posts are the attraction of a traditional house and also a large surface available to be eaten.
• Long vacancy. A long period during which nobody was there to notice grains on the floor.
• Furniture left behind. A chest or set of doors left in the house can hold a colony that survives treatment of the building and starts it again.
• No access. Some houses cannot be inspected below the floor or in the roof space at all.

Treatment, if it becomes necessary, is a different exercise from the usual. It involves injection into the timber and sometimes fumigation of the whole building. Fumigation clears what is present at that moment but leaves nothing behind that prevents reinfestation. Winged adults that arrive afterwards enter as before. The comfortable idea that you treat a house once and the problem is closed does not apply here either.

Old property is cheap for reasons, and this is one of the reasons that does not appear in the price discussion. It belongs with everything else in what a cheap Japanese house actually costs.

Before you buy, and while you own

The second row says record, and the word is deliberate. On a single visit, grains on a floor look like dirt. The fact that they have returned to a place already cleaned can only be established across several visits, and only if somebody photographed it the first time. Without a record there is nothing to compare.

What is worth checking on a purchase, and which of it can be answered from records rather than in person, is set out in what you must verify yourself before buying.