Clear Grade Sugi

Choosing a Wood Grade for Shou Sugi Ban

Catch up on our product selection walkthrough series here!

Part 1: Choosing a Shou Sugi Ban Surface for your Project

Part 2: How to Select an Oil Prefinish for Shou Sugi Ban Siding

If you’ve read through the first two posts in this series (linked above), you should be comfortable with all 4 of our different shou sugi ban surface options; sugi, Suyaki®, Gendai®, and Pika-Pika®. You should also have an idea of which oil prefinish color option you would like for your project. At this point in the process, it’s time to select a wood grade!

What is a Wood Grade?

Grade generally refers to the quantity and size of knots present in each board. We use Japan Agriculture Standards (JAS) for grading since it has been developed for and is the golden standard for grading the sugi species that we specialize in.

There are two JAS grades developed for sugi and shou sugi ban. Ko-fushi, small knot, which we call select, and Joko, high-grade no-knot, which we call Premium Clear grade in English. Select grade shou sugi ban has visible knots present and depending on the surface + color combination you’ve selected may stand out more or less. Premium clear grade wood (Joko grade) has very few if any small knots visible.

Select Grade Suyaki
Suyaki is only available in select grade

What Are Common Wood Grade Considerations?

In terms or strength and durability for siding applications, the two grades are equivalent. Joko premium clear grade comes from the older outside of logs felled from limbed forests, so the higher grade comes from larger, older trees with tighter growth rings. This means select grade has more heartwood and premium clear grade has more sapwood. Heartwood has higher mineral content but wider growth rings. These factors balance themselves out in terms of durability, so grade is purely a cosmetic decision.

Premium clear grade wood cost is about double select grade wood cost. This is a deciding factor for many projects.

Suyaki only comes in one grade (select) since knots blend in to the utilitarian, textured surface. With darker oil finish colors on Gendai and Pika-Pika, the knots blend in well. Lighter oil finish colors will accentuate the knots for more character.

Select grade wood adds character and is very affordable. Premium clear grade wood is less busy and if often specified for modern, minimalist, and high-budget projects.

Does Wood Grade Matter?

Structure and durability, NO. Aesthetics and budget, YES.


  • MixedBeans says:

    Great information. I’ve been told knots to stay away from knots because as the wood expands and contracts that may introduce water in the gaps betwen then knots and the rest of the board and that water may get trapped..

  • Thomas Casten says:

    I have been a climate change warrior for over 45 years. Sugi Ban life keeps the carbon from degrading for much longer than conventional cedar siding. Kudos. The key insight from these many years is to work with nature. Trees evolved with branches and branches create knots in the wood grown after the year the branch sprouted. I will use the knotted wood as part of my passion to work with nature.

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