6 ideas
Kohara's tests on old temple timbers found that hinoki does not begin decaying once cut: its strength and stiffness rise for roughly two centuries after felling, then decline so slowly that 1,300-year-old members perform about as well as fresh wood. A cut tree therefore has a second life as timber roughly as long as its growing life, and a thousand-year tree can yield a thousand-year building.
Each tree carries a kuse, a built-in tendency to twist, bend or pull that it got from its growing conditions, and that tendency persists after the tree is sawn. Instead of cutting timbers to erase this, the master carpenter pairs members whose tendencies oppose each other so their stresses lock the frame tighter over time. Assembling the structure is really assembling the trees' characters, and combining people with different temperaments on a crew follows the same logic.
A tree from a mountain's south face should go on the building's south side, and wood from the north side of the slope should face north. Timber keeps the orientation and exposure it grew under, so placing it the same way lets it resist sun, wind and moisture the way it already adapted to. The carpenter's instruction is to buy the whole mountain rather than individual logs, so that he knows each tree's origin before deciding where it goes.
He calculated that the wood members would compress and settle over centuries, and that the two pagodas would come level only after hundreds of years. The design targets the building's shape at a time scale beyond anyone now alive, not its appearance at completion.
Dismantling Hōryū-ji during the Shōwa restoration showed that the original Asuka-period work was the soundest, and later repairs got progressively worse as newer tools and shortcuts came in. The yariganna spear plane leaves a surface that sheds water and resists rot better than the smoother modern plane. When a technique is judged by efficiency, the knowledge that made the old work last is lost.
Nishioka argued against engineers who wanted steel reinforcement in the pagoda reconstruction. Iron rusts and concrete lasts perhaps a century, so a rigid modern material inside a flexible wooden frame becomes the point of failure. When judged over a thousand years rather than decades, the apparently strong modern choice is the fragile one, and compatibility with wood's movement matters more than raw strength.