Ne Tsugi 根継ぎ

Assembly insights

Ne Tsugi literally means "splicing the roots." Skilled miyadaiku cut out the deteriorated section of an old post and splice in new material using matching joinery—often Kanawa Tsugi or similar scarf joints with T-shaped stub tenons. The process demands temporary support of the structure, precise matching cuts on existing and replacement timber, and assembly without compromising the building. Commonly seen in temple and shrine restoration throughout Japan.

Historical context

Ne Tsugi has been essential to preserving Japan's wooden heritage for centuries. As timber posts in temples, shrines, and traditional houses succumb to moisture and rot at ground level, carpenters developed techniques to replace only the damaged portion rather than the entire column. This approach honors the original material while extending the life of structures by decades or centuries.

Construction steps

1. Support the structure safely using temporary beams, posts, and jacks before any cutting.
2. Cut out the rotted portion of the post, creating a clean square or angled face.
3. Fashion the replacement piece to match, creating identical joinery on both halves.
4. Use Kanawa Tsugi or a similar scarf with T-shaped stub tenons and optional wedges.
5. Assemble the joint and remove temporary supports once the splice is secure.

Where to see this joint in Japan

• Edo-Tokyo Open Air Museum — Tokyo — restored historic buildings
• Ise Grand Shrine — Mie — 20-year rebuilding cycle

Variations

The most common joint used in Ne Tsugi is Kanawa Tsugi, with identical joinery on each half that slides together and locks with a wedge. In refined applications, stub tenons can be hidden within the wood for a cleaner finished appearance. Some repairs use simpler scarf geometries when the post is not heavily loaded.