Inside Japan’s Unique Wooden Shingle Roofing Technique - Part 1

Hinoki, Japanese cypress.

Hinoki, a specialty of our country, has long been used in many shrine-related constructions as high-quality building timber.

However, hinoki is important not only for its wood.

The bark of the hinoki tree is another essential element.

since ancient times the roofs of old texts shrines and temples have been thatched with hinoki bark known as hiwada hiwada roofing this method fully utilizes nature's blessings and highlights the beauty of the bark

The technique of thatching roofs with hiwada and kokera, thin wooden shingles, is unique to Japan, refined over many years and passed down by our ancestors.

Now, let us introduce some representative buildings that use Hiwada and Kōkera roofing.

One example is Miyajima, part of the Japanese archipelago.

The Itsukushima Shrine, designated a World Heritage Site, harmonizes beautifully with nature.

Facing the sea, its roofs are thatched with Hiwada.

The Hiwada roofs made from Hinoki bark blend seamlessly with the island's greenery.

The shrine contains many buildings designated as national treasures and important cultural properties.

Most of their roofs are covered with hiwada.

The shrine's development to its current scale was supported by the power of Taira no Kiyomori, and hiwada roofing suits it perfectly.

Semyoji Temple, located in the ancient land of Omikuni on Mount Kotoyama, is believed to have been reconstructed in the old century.

Its main hall and three-story pagoda are designated national treasures.

They exemplify traditional Japanese styles, and their roofs are thatched with hiwada.

However, the hiwada applied about 30 years ago began showing signs of deterioration.

Re-thatching work began in 2001, Heisei 13.

Over 800 years, these two buildings have been re-thatched multiple times.

This superior technique has never faded and has been continuously inherited to this day.

Kongabui Temple on Mount Koya, founded by Kabo Daishi Kuke.

Its center, the Kondo, main hall, has the Fudodo, Hall of Fudomu, to its east, designated as a national treasure.

Fudodo, enshrining Fudomu, is built in the Irimoya-Zukuri style and has a complex, intricate roof.

Its Hiwada roof was rethatched during dismantling and repair work in 1999, Heisei 11.

Hiwada, which provides a soft appearance, is ideal for such subtly curved roofs.

Slightly north of central Hiroshima lies Anrakuji Fudoin Temple,

The Kondo of Fudoin, built in the Irimoya-zukuri style with a makoshi, pent roof, is a national treasure and the largest surviving Zen-style Buddhist hall from the medieval period.

Its roof is thatched with kokera shingles, well suited to the strongly curved Zen-style architecture.

Kokera roofing uses thinly split boards of cedar or cypress.

Though the technique and finish are similar to Hiwada, Kokera appears somewhat lighter.

In Sendai, the city of trees, stands Osaki Hachimangu Shrine, built by Date Masamune.

Its main and worship halls are connected by a stone corridor and designated as a national treasure.

The intricately designed roof is covered with kokera, which is more suitable than tiles for such shapes.

Many distinguished Japanese buildings use hiwada and kokera roofing.

These techniques are unique to Japan and embody a culture that lives in harmony with nature.

In autumn, when the forests turn color, Hinoki bark is stripped.

This bark becomes the raw material for Hiwada roofing.

The people who strip the bark have long been called Motokawashi.

Using spatulas made from flexible wood, they carefully peel the bark.

A key technique is leaving a single pink inner layer of bark intact.

This preserves the tree's vital cambium layer.

Burinawa, swing rope.

Hinoki trees are tall, sometimes reaching 20 to 30 meters.

Motokawashi use swing ropes to climb and work on the trees.

These are about 20 meter ropes with sticks tied at both ends.

The ends are thicker than the center to prevent slipping.

These are called buribo or tegi.

The stick is wrapped around the tree to secure the rope.

The climber steps on the stick and secures their body with a safety belt.

This allows both hands to be free to strip the bark.

The bark is carefully peeled upward using the spatula.

When the strip reaches five or six meters, it is cut and dropped.

The key is to let the bark land softly to avoid damage.

When climbing higher,

The lower rope is detached and re-secured.

Then, the climber secures the belt again.

Some motokawashi do not use safety belts, instead securing their bodies with extra rope.

Though the work looks dangerous, they always maintain three-point contact until they're fully secured.

They peel up to where the branches become dense and the bark is unusable.

It takes about one to two hours to peel a single tree.

Since World War II, hiwada production has declined.

Chronic shortages have been a problem.

One cause is the aging of mota kawashi.

But recently, efforts to train successors have borne fruit, and young people have entered the trade.

Peeled bark is sorted by width and thickness, then bundled with bark scraps.

Motokawashi and other craftsmen avoid waste and make full use of what's on hand.

The peeled Hiwada is transported.

Along with training successors, growing Hinoki trees is also crucial for Hiwada production.

Once the bark is stripped, the tree protects itself by producing new bark through accelerated growth.

After about 10 years, the bark can be harvested again.

Trees that are regularly stripped have their branches pruned and are protected from pests entering the bark, resulting in increasingly beautiful hiwada.

After carrying the hiwada to where vehicles can access, the motokawashi cuts the bark to length.

Using a traditional ruler, the sakubo, the bark is measured and then cut with a large specialized knife.

The standard sakubo length is 2 shaku 5 sun, about 75 cm, but there are also 3 shaku or 1 shaku 5 sun variants, and the bark is cut to different lengths depending on its intended use.

Hiwada is never harvested during spring to summer, when hinoki trees grow most actively.

The peeled bark is bundled into 30 kilogram units called hito maru.

It takes six to seven such bundles to cover one subo, about 3.3 square meters of roof.

The harvested hiwada is then passed to the fukushi, roofing craftsman, who shapes it for roofing.

This preparation process is called koshirae,

The koshiraya is performed on a workbench made from cross-sections of fine-grained wood such as hinoki or pine.

Using a specially shaped blade known as the hiwada knife, knots, resin, and other imperfections are shaved off, and the thickness is evened out.

This rough trimming is referred to as araikawa, rough skinning.

Thick pieces of bark are sometimes split into two or three thinner pieces.

Some thicker pieces are sorted out for special uses, such as uamakawa, top layer bark.

While not flashy, this work is essential for Hiwada roofing.

After washing, the bark proceeds to the tsutsurikawa process.

The hiwada is finally shaped into its roofing form.

The most common form made is hirakawa, flat bark.

A standard hirakawa is two shaku five sun long, five sun wide at the mouth, bottom edge.

Three soon wide at the tail, top edge, and five to six ream, approximately 1.5 to 1.8 millimeters thick.

To make a five soon mouth, narrower pieces of bark are combined and joined by tapping.

The pointed back of the Hiwada knife along shallow joints, though it looks simple, this joining requires refined skill.

Two or three pieces are combined, and the mouth and tail are trimmed to set lengths.

The edge of the mouth is trimmed straight.

This completes the Hirakawa.

30 of these are bundled together, and four such bundles make one ashi foot.

A craftsman had to make three bundle of Hirakawa per day to be considered fully qualified.

Next is the special purpose dogokawa, shaped for curved parts of the roof.

These are generally called namakawa raw bark.

High quality bark, cut in half, is used to make namakawa.

First, both ends are trimmed to adjust the tail width to 2sun5bu, approximately 7.5cm.

The trimmed pieces are saved for Nokizuke, Eve's tiling.

No piece of Hiwada is ever wasted.

The mouth is trimmed to length.

The edge of the mouth is shaped into a gentle curve for use on curved roof sections.

Accordingly, a pre-curved knife is used for trimming.

In this way, the various types of hiwada for roofing are prepared.

Stacking eaves tiling.

During the tsutsuri process, small pieces are used for eaves tiling.

Careful stacking makes site work more efficient.

These are finished hiwada pieces.

Those used on flat parts of the roof are called hirakawa.

The special use ones are called dagukawa.

With koshirai complete, preparations for hiwada roofing are ready.

Logs of sawara, Japanese cypress, are piled up.

Sawara and sugi, Japanese cedar, are used as raw materials for kakera roofing.

In some regions, chestnut trees are also used.

After felling, sawara logs are left to season for six months to a year, then cut into one saku, approximately 30 centimeters, lengths.

This process is called tamagiri block cutting.

The white sapwood of the cut saguaro is then removed with a large knife and a mallet.

The red heartwood is used for coquera shingles.

The sawara logs, with sapwood removed, are then split in a process called mekanwari, orange sectioning.

Mekanwari divides the log into six or eight equal pieces, like orange slices.

Since conifers like sawara split cleanly, the logs can be neatly divided using only a large knife and a mallet.

As such, sawara and sugi, which have a straight grain and contain oils that repel water, are ideal and commonly used materials for kakera reefing,

The mecanwery split logs then proceed to kidori grain sorting.

Only the straight-grained parts are used for kokora.

These sections are trimmed with a kidori knife.

During this, exact dimensions are ensured.

The trimmed material is further split into eighths to make kokera shingles.

If the original Kidori thickness varies, the final shingles will also vary in thickness.

The edge of the Kidori prepared material is shaved with a tool called sen, a draw knife.

This edge is the only part visible once installed, so it is given a decorative finish.

After finishing the edges, the final step is kawari, fine splitting.

A small splitting knife is placed halfway through the board, hit with a mallet, then twisted to split.

Because of this twisting motion, it is sometimes called koyawari.

This process divides each piece into eight thin shingles, completing the kokera material.

The thickness is reduced to just under one bu, about three millimeters.

Splitting such thin material accurately in half with a knife requires true craftsmanship

The finished Kokkara materials are bundled into 12-13 kg units called Ichiwa.

Laying out one Iwa of Kokkora in a line spans up to 15 ken .

For shipment, two Iwa are bundled into one Ashi .

Whether using Kokkara or Hiwada, one Ashi is enough to cover a single roofing section.

Oyabe City, Toyama Prefecture.

Beside National Route 9 lies the Sakuramachi Archaeological Site.

This site spans the entire Yaman period, from the early phase 12,000 years ago to the late phase 2,300 years ago.

Excavations revealed processed materials with drilled holes, confirming that raised floor buildings already existed in the Yaman era.

Roofing beams were also discovered, and the bark of Japanese walnut was used as roofing material.

A raised floor structure has been reconstructed, faithfully replicating a building of the Yaman period.

Like the artifacts, the reconstructed roof uses walnut bark for the base layer, topped with reed thatch,

Thanks to this site, we now know that the practice of using bark as roofing material dates back to the Yaman period.

Roofing materials evolved with time, from reed and straw to the use of tree bark, eventually progressing to Itabuki, splitting wood into planks and thatching roofs with them.

The Sese-Amoto Shrine at Itsukushima Shrine still has a roof made with Itabuki.

With cultural exchanges between Japan and China during the time of Kentsuishi and Kentoshi envoys, many techniques were introduced, including roof tiles.

Tile roofing spread quickly, shrines and temples like Hōyu-ji from the Asuka and Tempio periods mostly had tiled roofs.

Later, Japan developed its own architectural styles, one such style was the Tahoto, multi-story pagoda.

The oldest surviving Tahato from the early Kamakura period does not have a tiled roof, but is thatched with Hiwada.

The master builder at the time likely thought Hiwada roofing best suited the elegance of native Japanese culture.

Later Zen Buddhism was introduced by monks and its architecture strictly followed Chinese styles.

However, the Jizo Hall at Shofuku-ji, a typical Zen complex, does not have tiles, but is thatched with uniquely Japanese kakera.

Thus, hiwada and kakera roofing techniques were likely established in the Kamakura period.

With improvements over time, the skills of thatchers have been passed down continuously.

the five-story pagoda of Myōjoji Temple in Hakui, Ishikawa Prefecture.

While most buildings in the temple complex use kōkera roofing, only this pagoda has a thick four-bu or more roof, thick plank roofing.

Japan still preserves many structures designated as cultural properties.

About half of them have roofs that are thatched with hiwoda or kōkera.