Sugi — Cryptomeria japonica
Japan's national tree and the country's largest plantation species. Light, dimensionally stable, easy to work — the workhorse of Japanese carpentry for more than a thousand years, and the traditional substrate for Yakisugi cladding. Class 2 — Durable heartwood with significant variation by source and cultivar.
Sugi products
Raw Sugi lining & cladding for interior use, plus the full Yakisugi family — Sumi (deep-charred bare), brushed-charred with coloured coatings, and PU-coated charred for high-traffic applications.
Technical ReferenceSummary
Sugi is the most widely planted timber species in Japan and the country's national tree, occupying the largest plantation area of any species. The Nihon Shoki, Japan's first authoritative history, records the instruction: "build a boat with Sugi or camphor tree, build a palace with Hinoki, and make a coffin with podocarpus." Sugi has shaped Japanese architecture, joinery, and craft tradition for more than a thousand years — from temple framing and shrine avenues to sake barrels, geta, and the cedar-lined avenues of Nikko.
Sugi heartwood is rated Class 2 — Durable for above-ground exterior use. Old-growth and red-heartwood Sugi performs at the higher end of the durability range; plantation second-growth performs at the lower end. The traditional Japanese answer to extending Sugi's exterior service life is Yakisugi — surface charring, which adds a durable carbonised layer and is the standard preparation for exterior cladding.
Class 2 of 4
Character & Appearance
Sugi heartwood ranges from pale pink through warm amber to deep reddish-brown; the sapwood is straw-coloured and clearly demarcated. The grain is straight and pronounced, with a medium even texture, and the timber carries a soft characteristic fragrance.
Sugi is light, dimensionally stable, and easy to work with hand or machine tools — one of the reasons it is the workhorse of Japanese carpentry. It takes finishes well and holds fixings reliably. Its tannin chemistry makes it the traditional substrate for Yakisugi (charred cladding); its low density and straight grain make it the standard species for sake barrels, where it imparts the signature aromatic profile of taru-zake.
Species & General Properties
Mechanical & Physical Properties
| Property | Unseasoned | Seasoned |
|---|---|---|
| Specific gravity (12% MC) | — | 0.36 |
| Specific gravity (basic) | — | 0.33 |
| Average dried weight | — | 360 kg/m³ |
| Shrinkage — radial (green to oven-dry) | — | 2.1 % |
| Shrinkage — tangential (green to oven-dry) | — | 6.8 % |
| Shrinkage — volumetric | — | 10.5 % |
| Modulus of rupture (bending strength) | — | 36.4 MPa |
| Modulus of elasticity in bending | — | 7.65 GPa |
| Crushing strength (parallel to grain) | — | 28.0 MPa |
| Janka hardness | — | 1,420 N |
Recommended Applications
Sugi's combination of low density, dimensional stability, ease of work, and warm tonal range makes it the most versatile of the Japanese softwoods. For exterior service, the traditional and recommended preparation is Yakisugi (surface charring), which substantially extends service life beyond untreated Sugi performance.
Specification Notes
- The Class 2 rating applies to heartwood only. Sugi sapwood is not naturally durable and should be excluded from exterior use, or confined to protected internal applications.
- Sugi is not listed by name in AS 5604, which covers timbers commercially harvested in Australia. Class 2 status is specified by equivalence to the international decay-resistance scale, citing Scheffer & Morrell (1998) and the underlying Matsuoka et al. (1970) field-test data.
- Recommended spec wording: "Sugi (Cryptomeria japonica) heartwood — AS 5604 Class 2 above-ground durability (by equivalence to Scheffer & Morrell, 1998)."
- Source matters. Old-growth, red-heartwood, and island-variant Sugi (Yakushima, Akita, Yoshino) perform at the upper end of the durability range. Plantation second-growth Sugi performs at the lower end and should typically be specified with surface treatment for exterior use.
- Yakisugi (charred Sugi) is the traditional Japanese preparation for exterior cladding and substantially extends weathering and decay resistance through a carbonised surface layer. Yakisugi is the recommended specification for most exterior cladding applications.
- Durability ratings address biological decay only. Bushfire performance (AS 3959, BAL ratings) is assessed independently and must be verified separately for applicable zones.
References
Speccing Sugi or Yakisugi for a project?Sugi for a project?
Authentic Yakisugi imported from Japan, plus raw Sugi for interior cladding and joinery. We hold stock in Brisbane and machine to your profile. Talk to us about sections, length and colour.