Joining wood, building in wood: Japanese timber today

From traditional joinery that locks wood to wood without nails, to thick cross-laminated panels. Japanese timber construction was once shut out of large buildings for fear of fire, then returned as the laws were rewritten. We read the shapes of joints, the differences between systems, and the timber lodgings Tadao Ando chose on Naoshima.

Many ways to build in timber

Timber construction covers very different ways of building. There is the “traditional method” that survives in temples and old farmhouses; the “post-and-beam method” used for most Japanese houses today; the North American “platform frame”, known in Japan as two-by-four; and CLT, made of thick laminated panels. All are wood, but the way each resists earthquakes and loads is entirely different.

• Traditional method: joints are made by joinery alone, without metal reinforcement. Clay walls, through-ties (nuki) and deep head-beams resist earthquakes. Many temples and houses also stand on ishibadate foundations, with posts simply set on foundation stones.
• Post and beam: the method defined in the Building Standards Act. Joints between posts and beams are reinforced with metal fittings, and braces or sheathed walls resist earthquakes.
• Platform frame (2×4): floors and walls of timber frames sheathed in structural plywood, built up like a box. Technical standards were set by a Ministry of Construction notice in 1974, opening it to general use.
• CLT (cross-laminated timber): thick panels of sawn boards glued with their grain at right angles. Since a 2016 notice, CLT buildings no longer need individual ministerial approval.

Joining wood to wood: splices and connections

The heart of the traditional method is how pieces of wood meet. Joints that lengthen a member are called tsugite (splices); joints that meet at an angle are called shiguchi. Two classic splices are the sickle splice and the dovetail splice.

The sickle splice (kama-tsugi) fits a tenon shaped like a sickle’s head into a matching socket, and is said to have been used since the 7th century. Used mainly for beams, it resists being pulled apart. The dovetail splice (ari-tsugi) joins the ends of members with a flared, dove-tail shape. Other splices, such as the kanawa-tsugi, bring together angled faces and lock them with a wooden peg.

Another defining element of the traditional method is the nuki, a horizontal member passed through the posts. Depending on height it is called a hi-nuki, koshi-nuki or ji-nuki. Interlocked posts and nuki give the whole frame a supple strength against shaking.

Large timber buildings, once shut out

Wood burns. The Building Standards Act of 1950 set fire-prevention and fire-resistance standards and restricted the use of wood in large buildings. In 1959 the Architectural Institute of Japan is said to have called for a ban on timber construction, citing fire and typhoons. Large timber buildings disappeared from postwar cities.

The tide turned in 1987 with “charring-depth design”: the part of a member that will burn to charcoal in a fire is allowed for in advance, and the unburnt core carries the building. This made large timber buildings with heavy sections possible again. The layer of char on the surface slows the fire’s progress inward, turning a property of wood to its advantage.

The rules continued to loosen. With the 1998 amendment (in force from 2000), performance-based design allowed fireproof buildings in timber. In 2019, the size of timber building that need not be fireproof grew from “up to 13 m high and 9 m to the eaves” to “up to 16 m high and three storeys”.

A 2010 law encouraged the use of wood in public buildings, and in 2021 it was revised to cover private buildings as well. The share of public buildings built in timber rose from 8.3 percent in FY2010 to 13.9 percent in FY2020, and to 29.7 percent among low-rise buildings.

When an architect of concrete chooses wood

Tadao Ando, known for exposed concrete, has also built in wood. The Japan Pavilion at Expo ’92 in Seville was a five-storey timber structure with a clear span of 60 m; the Bureau International des Expositions describes it as one of the largest timber buildings in the world. At Nangakuzan Komyoji temple in Saijo, Ehime, completed in 2000, the main hall reveals timber members layered and supporting one another.

At Benesse House on Naoshima, Park and Beach, opened in 2006, are built with glued laminated timber. Official materials note that Park is unusual among Ando’s buildings in being built of timber. The museum on the hill is reinforced concrete; the lodgings by the shore are wood. The same architect chooses his material to suit the place.

Concrete on the hill, timber by the shore: the difference in material answers a difference in the land.

Timber landmarks you can stay in

Among classic timber hotels is the main building of the Nara Hotel. Opened in 1909 and designed by the office of Tatsuno and Kataoka, it is built of timber with some brick. In October 2026, the Council for Cultural Affairs recommended its designation as an Important Cultural Property; it would be the first building in Japan still operating solely as a hotel to receive the status.

Kasui-en in Kyoto is also a sukiya inn that combines timber with steel to achieve its thin, light roofs. Timber construction lives on in hotel architecture, combining traditional craft with new technology.

Look at the wood when you stay

When you stay in a timber building, look for the places where posts and beams meet. Are they fixed with metal, or locked wood into wood? At night, in a quiet room, a timber building sometimes ticks softly as temperature and humidity change. It is a moment to feel, with your body, that wood is a living material.

Where to see this technique

• Benesse House (Naoshima, Tadao Ando): Park and Beach, built with glued laminated timber
• Kasui-en (The Westin Miyako Kyoto) (Kyoto, Togo Murano): thin roofs of timber combined with steel

Sources

• National Research Institute for Earth Science and Disaster Resilience, press release, 20 December 2010
• JAANUS: nuki, kamatsugi, aritsugi; Kotobank: platform frame construction
• Forestry Agency, Annual Report on Forest and Forestry FY2021; Forestry Agency CLT notices; MLIT press release, 29 March 2018
• Building Research Institute lecture (history of fire rules for timber, FY2023)
• President Online (on the 1959 call by the Architectural Institute of Japan)
• Benesse Art Site Naoshima press release; Ehime Prefecture (Komyoji); Bureau International des Expositions
• JR West press release, 16 October 2026 (Nara Hotel main building)