“Authentic” Japanese Cedar Does Not Mean Better

Some suppliers may argue that their knotty timber is the more “authentic” choice for a charred timber finish because traditional Japanese Yakisugi was often made from Sugi, or Japanese cedar, and commonly included knots. But this is not the right way to use the word authentic.

Authentic does not automatically mean best performing. It often means historically typical.

Unpruned Sugi Forest

Why was Knoty timber used:

Knotty timber was used historically in Japan because it was available, familiar, local, and abundant. Clears grade timber was simply not available. Sugi is deeply embedded in Japanese timber culture and has long been used for construction and cladding, including Yakisugi. Some modern suppliers still describe Sugi as the benchmark species for traditional Yakisugi, but that does not mean Sugi performance is the best option when charred. If fact today it is commonly considered the minimum threshold for charred timber finishes.

The important distinction is this: traditional material choice and modern quality control are not the same thing.

Left shows Clear grade timber VS right Knotty grade timber

Modern Timber options have improved charred timber finishes:

Historically, builders used the timber grades that were practically available to them. Today, we have better grading, pruned forests giving clear grade boards, improved timber species through selective breeding. That means we can produce a clean, more stable, more predictable charred cladding finish than was possible when timber selection was limited by local availability.

12 months after installation knots have lost their char

Why Char falls off knots

This is where the “authentic” argument starts to fall apart. If knotty timber produces a less consistent char, more visible weathering around knots, and a higher risk of pale spotting across the façade, then it should not be defended simply because it feels traditional.

Knots are known to be denser than the surrounding timber, and research has found knot density can be significantly higher than clear wood; one study on white spruce found knots averaged 2.4 times the density of clear wood. (Wagner Meters) This higher density makes a knot harder to char than the surrrounding wood, and this char will fall off in 12 months.

A useful comparison is sailing. Historic wooden sailing ships were authentic, beautiful, and culturally important. But modern yacht design has moved on. Composite materials, engineered hull shapes, carbon fibre, stainless fittings, and modern sail systems outperform historical construction in strength, control, speed, and reliability. Nobody would seriously argue that an old timber sailing ship is automatically the best technical solution simply because it is more authentic.

The same logic applies to charred cladding.

Clears grade timber with no knots

Modern timbers produce better charred finishes.

Knotty grade timber may be historically familiar, but clear grade timber is a superior substrate for a premium charred finish. It chars more evenly, weathers more predictably, and produces a more controlled architectural surface. In that sense, clear grade timber is not less authentic; it is a modern improvement on the traditional process.

The real aim should not be to copy every limitation of historical timber supply. The aim should be to preserve the strength of the Yakisugi idea — a beautiful, carbonised, durable-looking timber surface — while using the best available timber grade to achieve a better architectural result.