Kuri: the chestnut that shares the pillar

Kuri is the wood that shows up in this file by mention before it gets a card of its own: the record on the kominka's anatomy names it, next to sugi, as a choice for the house's one indispensable post. Castanea crenata, the Japanese chestnut, is a hardwood with a reputation for outlasting the trees around it, and the reason sits in its chemistry as much as its grain.

What the wood is

Kuri is the Japanese member of the chestnut genus, Castanea, the same family that gave Europe its sweet chestnut. Japanese references describe its timber as hard, heavy and slow to rot; its European relative is a ring-porous hardwood whose grain runs from straight to spiral, with heartwood that moves from light brown towards a reddish-brown patina as it ages. European sweet chestnut, its closest documented relative, is rated durable to very durable against rot, a resistance that comes from a heavy load of tannins in the wood itself; the same tannins stain the wood on contact with iron. Japanese sources note the same heavy tannin load in kuri's bark and inner skin, and its timber has long been used for posts, house sills and railway sleepers, and carpenters who choose it do so for the same instinct: a hardwood that does not give up fast in damp conditions.

Where it is used

The clearest use on record in this file is the daikokubashira, the great central pillar of a kominka, where the anatomy card notes a single massive log of sugi or chestnut, chosen for its diameter rather than its straightness. A pillar carrying the crossing of a house's main beams for a century or more asks for exactly the property chestnut is known for: a wood that resists the slow rot a post can suffer at its base, where ground moisture and the open frame of an old house both reach it. In Japan the same reputation sent kuri into house sills (dodai) and railway sleepers, and archaeologists have found chestnut to be the main building timber of the Jōmon period, including the great posts at Sannai-Maruyama; in Europe the genus has long gone into fence posts, shingles and outdoor structures, on the same logic of durability bought by tannin rather than by density alone.

Working the wood

Chestnut dries evenly and holds its shape well once seasoned, which suits a post that is expected to stand still for generations. Its one well-documented weakness at the bench is a tendency to split under careless nailing or screwing, so pre-boring and patience at the fastener matter more with chestnut than with a gentler hardwood. The tannin that protects it against decay is the same compound that reacts with iron, so a fitting in brass, bronze or stainless steel keeps a chestnut member from staining itself from the inside.

Why it sits beside sugi, not against it

A kominka's central pillar is not a fixed recipe: sugi gives height, lightness and a fast, straight-grown log; chestnut gives a harder, heavier post with a longer memory for resisting rot at the base. The choice between them was a choice between two honest trade-offs, made by the carpenter against what was standing in the local forest and what the house needed most at its one irreplaceable post. A kominka with a chestnut pillar is not a lesser or a better house for it; it is a house whose carpenter weighed durability over ease of handling at the exact point where that trade mattered most.

The card, filed

Kuri earns its place in this index on a documented record of posts and sills and a family resemblance: it is one of the two woods this file has on record for a kominka's central pillar, and it belongs to a genus whose durability is well documented in its European relative. Where sugi offers a tall, light, fast-grown post, chestnut offers a harder, slower one that asks more of the carpenter's fasteners and gives back a longer resistance to rot at the base. The two are filed side by side here for that reason, not because either is the better wood in the abstract.