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Industrially precut timber framing has become the predominant house construction method throughout Japan. In our first short documentary, we explain the process from factory floor to building site. Like so much of its traditional culture, Japan has developed a highly efficient technological adaptation of an age-old building technique.

BAKOKO is a international design practice based in Tokyo, Japan, founded by architects Alastair Townsend and Kayoko Ohtsuki.


Japan's traditional architecture is famed for its intricately carved joinery.

Forgoing nails and screws, master builders used interlocking joints to construct robust wooden buildings that have remained intact for centuries despite frequent earthquakes.

Like other aspects of its culture, Japan has successfully applied technology to preserve and modernize this traditional building method.

The precut method uses robotic machinery to cut each interlocking joint in seconds.

Throughout the 1990's robotically manufacturing timber frame houses skyrocketed. Today it is the standard house construction throughout the country.

We are currently building a beach house for a private client in Chiba Prefecture, on the Pacific coast southeast of Tokyo.

Our blueprints were re-drawn by the precut timber supplier into a set of schematics.

The symbols at the junction of each post and beam denote what type of joint will be cut to fit them together.

To better understand the process, we decided to tour the factory while the timber for the home's structure was being cut.

In a former Hitachi factory about 30 kilometers from the site, five workers produce the timber structure for 800 - 1,000 homes each year (with the capacity to handle up to 4,000).

Purpose-built machinery, manufactured by the Heian Corporation, is completely automated, taking square-cut lumber and processing it into stack of pre-jointed and numbered posts and beams.

Each job is input into the machinery from specialized software. The operators' only task is feeding in the appropriate lumber for each job listed in the computer's queue.

There are separate machines for cutting the posts and beams.

First, the dimension of each timber is checked and cut to length by a large radial saw.

From there, it is whisked down a conveyor belt to a large wheel-like armature with five centrifugally-arranged drill attachments.

The spinning wheel allows the machine to mill a tenon (the protruding part of the joint) onto both ends of each post and beam.

A separate part of the machine mills the mortises (or sockets) at exact locations along length of each member.

Along the way, each piece is marked with a unique number so that it can be quickly identified and assembled in the correct place when it arrives on site.

Finally, the wood is stacked, wrapped, and ready for delivery.
It took only a day to erect the precut timber frame of the beach house.

Two skilled carpenters (or daikusan) are working on the job. But to erect the frame everyone from the electrician to the interior decorator is called upon to help.

The pre-numbered members are hoisted by crane and fitted together with the help of a large wooden mallet.

The workers obviously enjoy the process which is akin to piecing together a large wooden puzzle.

The joints are reinforced with steel bolts, providing an additional factor of safety in the event of a large earthquake.

Only some parts of the angled wooden truss reinforcing the southern facade could not be cut by the precut machinery. These had to be hand-cut by the daiku-san.

Despite a long-term recession and a shrinking population, Japan continues to rapidly build new homes.

But the workforce of skilled carpenters (or daiku-san) is also aging. It's unlikely homebuilding in Japan could continue without relying on automation.

With precut, the time and cost of cutting and shaping timber joints on-site, according to long-held building tradition, is greatly reduced.
Using automation, Japanese builders – renowned for their skill and obsessive attention to detail - can efficiently achieve millimeter accuracy quickly whilst eliminating nearly all on-site waste.

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