Kendo-jo Flooring Experts

Wood species used

The following comments are just my personal opinion as both a practitioner of kendo and as a wooden flooring specialist.
There are other, different viewpoints and opinions of merit. This information should be used for reference only.

Photo Type Shape Color Section Hardness Irregularity
in the aging
Foot touching the surface Service life Cost Subjective evaluation Determination
Sugi Solid red No Just Medium Just High Medium Even among sugi, compared to “genpei”... AA
Sugi Solid red Yes Just Large Possible Medium Low Even among sugi, compared to “genpei”... B
Sugi Solid red
white
No Soft Rough Just Low Low In the early days after a solid wood ... D
Sugi Solid red
white
Yes Soft Rough Possible Lowest Lowest As the floor becomes used over time,... E
Sugi Laminated red
white
No Soft Large Possible Low Medium There is a large difference when ... E
Hinoki Solid red
white
No Just Small Slip High High Along with sugi, Japan’s ... B
Hinoki Solid red
white
Yes Just Medium Slip Medium Low Along with sugi, Japan’s ... B
Hinoki Laminated red
white
No Just Large Slip Low Medium Just like red pine, the difference .. D
PIne Solid red
white
No Little hard Small Just High Highest Red pine is widely regarded... A
PIne Solid red
white
Yes Little hard Medium Possible Medium Medium Red pine is widely regarded... C
PIne Laminated red
white
No hard Large Possible Low Medium There is a very big difference ... E

Solid wood sugi heartwood, knotless or limited small knots

Even among sugi, compared to “genpei” sugi (alternating red heartwood/white sapwood), solid sugi heartwood will have less friction on the surface; it will wear more evenly giving it a longer useful life; and it will have a more comfortable feel as the feet step and slide on the floor’s surface.

Just using sugi will not necessarily give you a soft, elastic kendo-jo floor with a good feel to it. In many cases, the structure beneath the flooring is just as important.

Comparing red heartwood and white sapwood, it is often said that the red heartwood is stronger due to having a higher density or having more “oil” to it. Although it may well express the overall gist of the issue, the actual basis behind this is probably different. The heartwood’s slightly higher density would be expected to give a slightly better resistance to friction wear, but a large difference in density between the heartwood and sapwood is not all that often seen. What about the “oil” in the wood? This has been said from long ago, but oil is most easily taken from the sapwood.

The reddish heartwood has various chemicals and minerals naturally incorporated into the wood. This is usually generically called extractives. Although which extractives do what is not well known, it is believed that the extractives are one reason for the greater resistance to wear from friction.

Heartwood and sapwood also differ in the angles of the microfibrils within the wood. This may also impact the resistance to friction wear of the wood. They white colored wood is almost entirely found in the sapwood part of the tree. The growing tree needs to pull water up through the sapwood, whose cells (and a greater proportion of the microfibrils) are pretty much straight up and down and whose pores between cells are wide open.

Red heartwood near the core material where the microfibrils are angled and all the heartwood has closed pores. The cells with closed pores can be likened to a balloon, and like a balloon, could be imagined to have better bounce or elasticity. However, I don’t mean elasticity in the Young’s Modulus of Elasticity (a measure for predicting deflection) sense for the word.

Most materials become hard when they become old. For the heartwood of sugi, this would apply to the oldest juvenile wood within the core, and this portion of the tree is often the hardest. We also want to be careful when drying the wood. If the wood is dried too much or on too hard of a schedule, the resistance to wear may be affected. The wood should be dried naturally with a little bit of kiln drying at the end for material to make a long lasting kendo-jo flooring.

For maintenance, just wiping the floor with a damp cloth upon every use will suffice.
Wood which is knot free or has only small tight knots will have little unevenness, and will give a floor a long life with little maintenance.

Wiping down the floor is an important part of kendo, and should always be done. A heartwood sugi floor which has been heavily polished through use will become as hard as pine. Hakudo Nakayama-sensei stated, “The best wood for kendo floors is the oldest possible sugi you can get.”

Solid wood sugi heartwood with knots

The heartwood of knotty sugi will have greater wear resistance than sapwood or “genpei” mixed heartwood/sapwood grades. The surface will also wear more evenly.
Just using sugi will not necessarily give you a soft, elastic kendo-jo floor with a good feel to it. In many cases, the structure beneath the flooring just as important.

Comparing red heartwood and white sapwood, it is often said that the red heartwood is stronger due to having a higher density or having more “oil” to it. Although it may express the overall gist of the issue well, the actual basis behind this is probably different. The heartwood’s slightly higher density would be expected to give a slightly better resistance to friction wear, but a large difference in density between the heartwood and sapwood is not all that often seen. What about the “oil” in the wood? This has been said from long ago, but oil is most easily obtained from the sapwood.

The reddish heartwood has various chemicals and minerals naturally incorporated into the wood. This is usually generically called extractives. Although which extractives do what is not well known, it is believed that the extractives are one reason for the greater resistance to wear from friction.

Heartwood and sapwood also differ in the angles of the microfibrils within the wood. This may also impact the resistance to friction wear of the wood. They white colored wood is almost entirely found in the sapwood part of the tree. The growing tree needs to pull water up through the sapwood, whose cells (and a greater proportion of the microfibrils) are pretty much straight up and down and whose pores between cells are wide open.

Red heartwood near the core material where the microfibrils are angled and all the heartwood has closed pores. The cells with closed pores can be likened to a balloon, and like a balloon, could be imagined to have better bounce or elasticity. However, I don’t mean elasticity in the Young’s Modulus of Elasticity (a measure for predicting deflection) sense for the word.

Most materials become hard when they become old. For the heartwood of sugi, this would apply to the oldest juvenile wood within the core, and this portion of the tree is often the hardest.We also want to be careful when drying the wood. If the wood is dried too much or on too hard of a schedule, the resistance to wear may be affected. The wood should be dried naturally with a little bit of kiln drying at the end for material to make a long lasting kendo-jo flooring.

When using knotty material, unevenness will develop around the knots. Also, parts of the knots will crack and fall out, resulting in the need for repairs and maintenance.
For ordinary maintenance, just wiping the floor with a damp cloth upon every use will suffice.

Wood which is knot free or has only small tight knots will have little unevenness, and will give a floor a long life with little maintenance. Wiping down the floor is an important part of kendo, and should always be done.

A heartwood sugi floor which has been heavily polished through use will become as hard as pine. Hiromichi Nakayama-sensei stated, “The best wood for kendo floors is the oldest possible sugi you can get.”

Solid wood sugi “genpei” mixed heartwood / sapwood clear or with small tight knots

In the early days after a solid wood “genpei” heartwood/sapwood floor is installed, other than color, there is little noticeable difference compared to heartwood grades.

However, after years of use, there will be quite noticeable differences in the wear between the sapwood and heartwood. This becomes uncomfortable to the touch as the kendo-shi uses the floor.

When dried properly in a kiln, bound proteins in the springwood are lost or destroyed. As the protein is lost, it is surmised that the cellulose and lignin separate. As it is dried, a kind of scum, similar to dead skin on people, arises from the surface of the wood. This might be lignin or cellulose.

The wood should be dried naturally with a little bit of kiln drying at the end in order to make material for a long lasting kendo-jo flooring.

On kendo-jo floors which have been heavily used, you will see a difference in the amount of wear between the reddish heartwood and the white sapwood.

In order to control and help even out the wear on the flooring when using “genpei” mixed heartwood / sapwood, you would need to diligently apply an oil coating to the flooring.

Compared to solid sugi heartwood, the running cost of “genpei” flooring will be higher.

Solid wood, knotty “genpei” (mix of heartwood / softwood)

As the floor becomes used over time, areas around knots and between the growth rings will show unevenness. After years, the springwood will wear more than the summerwood resulting in raised summerwood which becomes uncomfortable to the kendo-shi.

When dried properly in a kiln, bound proteins in the springwood are lost or destroyed. As the protein is lost, it is surmised that the cellulose and lignin separate. As it is dried, a kind of scum, similar to dead skin on people, arises from the surface of the wood.

This might be lignin or cellulose.

On kendo-jo floors which have been heavily used, you will see a difference in the amount of wear between the reddish heartwood and the white sapwood.

In order to control and help even out the wear on the flooring when using “genpei” mixed heartwood/sapwood, you would need to diligently apply an oil coating to the flooring.

laminated sugi flooring

There is a large difference when comparing solid sugi to glue laminated sugi flooring. Glue laminated flooring has superior dimensional stability which makes it suitable for dojos which are equipped with air conditioning and heating.

As you can see in the image, glue laminated flooring is made by gluing together strips of wood. Many pieces of wood are glued together in order to impart uniformity and stability to the product. However, it is difficult to say that this is the ideal flooring.

Also, the appearance of the laminated flooring gives the appearance of an industrial product, which gives the flooring a very cheap image.

Although the laminar of the flooring is randomly oriented with both quartersawn and flatsawn faces, it tends to be mostly comprised of quartersawn faces. This creates a floor which is slippery.

When the laminar are oriented radially (quartersawn), the latewood is oriented vertically. This is believed to reduce the pace of wear on the floor surfaces. However, as the floor is used, unevenness develops between the growth rings.

This unevenness is easily felt by the bare feet upon the floor and is somewhat uncomfortable.

Glue laminated flooring is made from kiln dried raw materials. As the seasons change such as from the rainy season to summer, the flooring shrinks and swells. After one full season, you can begin to see the ups and downs on the floor surface.

The eroding of the floor surface through friction is quite fast, and requires applications of oil to be diligently applied as part of the maintenance program. This is true for both sugi and non-sugi laminated flooring.

The durability of the glue laminated sugi flooring will be quite a bit less than solid wood sugi flooring.

Solid wood hinoki, clear or few tight knots

Along with sugi, Japan’s mountains are rich in hinoki. When performing “keiko” during the winter, hinoki flooring tends to become more slippery, but not as much as the glue laminated flooring of other species.

Hinoki can be compared to sugi, but sugi has a slight edge on “warmth” and also cost. Because of the warmth and feel on the feet, higher grade sugi is more commonly chosen.

Hinoki is sometimes chosen for dojo flooring by people who want it because it is used for the floor on the stage where Noh is performed. Hinoki in Noh stage flooring is used with the inside of the tree facing up. This is said to be for acoustic reasons.

The bow of the boards will be opposite depending on whether the boards will be oriented inside up or indside down. In Noh stages, the inside up orientation is believed to give better sound.

The purpose and characteristics of Noh and kendo flooring are quite different. If the flooring were laid in the inside up orientation, this would cause that the wood would split or separate in the wood grain and become unsuitable for a kendo-jo floor.

Through its long useful life, hinoki will develop a beautiful color and luster. However, it will become a little bit slippery. In terms of cost, high grade hinoki with no or few knots will be higher than sugi of the same grade.

Like other solid woods, maintenance is simple: just wipe down with a damp cloth.

Knotty hinoki

Along with sugi, Japan’s mountains are rich in hinoki. When performing “keiko” during the winter, hinoki flooring tends to become more slippery, but not as much as the glue laminated flooring of other species. Hinoki can be compared to sugi, but sugi has more “warmth” and costs less.

In terms of cost, knotty hinoki is similar to that of “genpei” sugi of a grade with few or no knots.
Because of the warmth and feel on the feet, higher grade sugi is more commonly chosen.

Hinoki is sometimes chosen for dojo flooring by people who want it because it is used for the floor on the stage where Noh is performed. Hinoki in Noh stage flooring is used with the inside of the tree facing up. This is said to be for acoustic reasons.

The bow of the boards will be opposite depending on whether the boards will be oriented inside up or indside down. In Noh stages, the inside up orientation is believed to give better sound.

The purpose and characteristics of Noh and kendo flooring are quite different. If the flooring were laid in the inside up orientation, this would cause that the wood would split or separate in the wood grain and become unsuitable for a kendo-jo floor.

Through its long useful life, hinoki will develop a beautiful color and luster. However, it will become a little bit slippery. After extensive use, there will be unevenness around the knots which will be noticeable. Like other solid woods, maintenance of knotty hinoki is simple: just wipe down with a damp cloth.

Glue laminated hinoki

Just like red pine, the difference between hinoki glue laminated flooring and solid wood flooring is like heaven and earth.

Glue laminated flooring has superior dimensional stability which makes it suitable for dojos which are equipped with air conditioning and heating. As you can see in the image, glue laminated flooring is made by gluing together strips of wood.

Many pieces of wood are glued together in order to impart uniformity and stability to the product. However, it is difficult to say that this is the ideal flooring. Also, the appearance of the laminated flooring gives the appearance of an industrial product, which gives the flooring a very cheap image.

Although the laminar of the flooring are randomly oriented with both quartersawn and flatsawn faces, it tends to be mostly comprised of quartersawn faces. This creates a floor which is slippery. When the laminar are oriented radially (quartersawn), the latewood is oriented vertically. This is believed to reduce the pace of wear on the floor surfaces. However, as the floor is used, unevenness develops between the growth rings.

This unevenness is easily felt by the bare feet upon the floor and is somewhat uncomfortable.

Glue laminated flooring is made from kiln dried raw materials. As the seasons change such as from the rainy season to summer, the flooring shrinks and swells. After one full season, you can begin to see the ups and downs on the floor surface. The eroding of the floor surface through friction is quite fast, and requires applications of oil to be applied at some time as part of the maintenance program.

Like other glue laminated flooring, the wear will be most pronounced in the radial (quartersawn) direction. Since most glue laminated flooring is manufactured this way, the surface will be worn down relatively quickly.

In areas where the lamina are oriented in a flatsawn manner, the wear on the surface compared to that of its surrounding laminar will become quite noticeable to the touch.

Similar to glue laminated floors of other species, the durability of the glue laminated hinoki flooring will not be high by any means when compared to solid wood.

In terms of total cost, the glue laminated hinoki floor will be about the same as a solid heartwood sugi floor with no or few knots, but may be higher depending on construction techniques used.

Solid wood, red pine, clear or small tight knots

Red pine is widely regarded throughout Japan as a good kendo-jo flooring material. Red pine has been widely used for dojo flooring. One reason for this is believed to be that many years ago, only red pine was available in large sizes or long lengths from old trees.

Normally, pine boards experience pitch seeping to the surface. In kendo, where the foot slides across the floor surface, it is easy to see why the presence of pitch makes the material unsuitable for dojo flooring. Another issue is that very little red pine is straight and true. This means the material is more prone to movement such as twisting and warping in various directions even after installation.

An old custom still in existence has been to utilize the red pine which grew on the grounds of the premises as dojo flooring. Also, getting one piece with length sufficient to reach end to end of the dojo often meant using red pine. It is safe to say that all the red pine dojo flooring in use today was not selected purely because it was thought to be the best material, but one of convenience and custom.

Nowadays, there are plantation forests with alternative species to red pine, so it can be expected that the use of red pine will steadily decrease as a dojo flooring material.

Extensive use of red pine will result in a floor with a beautiful reddish color and a wonderful shine. The surface will become easier to glide across and will become harder. If the grade of the red pine has few small tight knots or no knots at all, the unevenness between the growth rings due to wear will not be very noticeable when performing “keiko” practice.

Maintenance is simple: just wipe down with a damp cloth. In terms of cost, red pine has become a little expensive because of a diminished supply of logs due to losses inflicted by an exotic pest, the pinewood nematode.

Japan has many plantation forests planted after WWII, so material from these forests is more economical.

Solid wood, knotty red pine

Red pine is widely regarded throughout Japan as a good kendo-jo flooring material. Red pine has been widely used for dojo flooring. One reason for this is believed to be that many years ago, only red pine was available in large sizes from old trees.

Normally, pine boards experience pitch seeping to the surface. In kendo, where the foot slides across the floor surface, it is easy to see why the presence of pitch makes the material unsuitable for dojo flooring. Another issue is that very little red pine is straight and true. This means the material is more prone to movement such as twisting and warping in various directions, even after installation.

An old custom still in existence has been to utilize the red pine which grew on the dojo grounds as dojo flooring. Also, getting one piece with length sufficient to reach end to end of the dojo often meant using red pine. It is safe to say that all the red pine dojo flooring in use today was not selected purely because it was thought to be the best material, but one of convenience and custom.

Nowadays, there are plantation forests with alternative species to red pine, so it can be expected that the use of red pine will steadily decrease as a dojo flooring material.

Extensive use of red pine will result in a floor with a beautiful reddish color and a wonderful shine. The surface will become easier to glide across and the surface will become harder.

After extensive use, a knotty red pine grade will have a noticeable unevenness in the areas around the knots.

The uneven wear of the earlywood and latewood will be relatively gentle and less noticeable. However, taken as a whole, the unevenness will be noticeable.

Maintenance is simple: just wipe down with a damp cloth.
In terms of cost, red pine has become a little expensive because ofthe diminished supply of logs due to losses inflicted by an exotic pest, the pinewood nematode. Japan has many plantation forests planted after WWII, so material from these forests is more economical.

Glue laminated red pine

There is a very big difference between using red pine lumber and red pine glue laminated flooring for the kendo-jo. Although the same kind of wood, the floor will be completely different. About the only thing the same is the name of the tree.

Glue laminated flooring has superior dimensional stability which makes it suitable for dojos equipped with air conditioning and heating. The thought that a hard pine material is well suited for kendo-jo flooring only applies to solid wood. Glue laminated wood is a different matter.

It is inconceivable that glue laminated red pine could be said to be an ideal material for a kendo-jo floor. Directors of the dojos will tell you that the real reason pine has been used for dojo flooring is due to the fact that when they were built, long length material of sugi and hinoki from plantation forests were not available at that time. Only pine was available in the long lengths at the time.

It is common for pitch to occur on the surface of pine boards. Pitch will interfere with the gliding of feet across the floor during “keiko”, so using pine for kendo-jo flooring is inconsistent with the intended use.

As you can see in the image, glue laminated flooring is made by gluing together strips of wood. Many pieces of wood are glued together in order to impart uniformity and stability to the product. However, it is difficult to say that this is the ideal flooring.

Also, the appearance of the laminated flooring gives the appearance of an industrial product, which gives the flooring a very cheap image.

When the laminar are oriented radially (quartersawn), the latewood is oriented vertically. This is believed to reduce the pace of wear on the floor surfaces. However, as the floor is used, unevenness develops between the growth rings. This unevenness is easily felt by the bare feet upon the floor and is somewhat uncomfortable.

Glue laminated flooring is made from kiln dried raw materials. As the seasons change, such as from the rainy season to summer, the flooring shrinks and swells. After one full season, you can begin to see the ups and downs on the floor surface. The eroding of the floor surface through friction is quite fast, and requires applications of oil to be applied at some time as part of the maintenance program.

The durability of the glue laminated pine flooring will not be high by any means. In terms of total cost, the glue laminated pine floor will be higher than a solid wood sugi heartwood grade with few or no knots depending on construction techniques.