On a rainy day in late March, a group of people were making material to apply to the walls of a two-story concrete house going up in the city of Musashino in Tokyo.
They mixed earth with sand, quicklime, water and chopped straw.
With a trowel in one hand and a small wooden board for the earthen plaster in the other, they applied the material 10 to 15 mm thick on a wide living room wall.
Meanwhile, other walls were coated with quicklime mixed with water.
Called Nurikabetai (the Team to Plaster Walls), the workers are not professionals, but rather ordinary men, women and children who simply enjoy plastering.
“I enjoy plastering. I love playing with mud,” said Miyako Otomo, a Web page designer who was taking part in a group project for the first time. “I usually work on PCs, (but) I like doing things with my hands.”
The Tokyo-based Nurikabetai is a group of amateur plasterers who use earth or quicklime — natural materials — on the interior and exterior walls of buildings ranging from old farmhouses and warehouses to shops and bars.
Architect Gyo Katayama set up the group in 2000 with several students from his workshops on earth plastering.
“At the time, I didn’t think there would be a high demand” for plastering with the materials, said Katayama, who taught himself the plastering techniques. “But I thought the natural materials for plastering could attract some people who are (ecologically) conscious.”
Thanks to the reach of the Internet, the group now has 500 members nationwide on its mailing list, including some 200 who take part in the plastering projects.
Plastering walls with earth or other materials by nonprofessionals has been gradually spreading in Japan in recent years. Some companies have begun selling such ready-made materials for plastering.
Earth or lime plastering — traditional wall-coating methods — are suited to a healthy and ecological lifestyle, said Hideki Ishida, a professor of nature technology at Tohoku University in Miyagi Prefecture.
In fact, walls made with these materials naturally create a comfortable living environment, he said.
Earthen walls, for instance, keep indoor humidity between a comfortable 40 percent and 70 percent, while a lime coating can prevent mold from growing on walls and has a water-shedding effect, Ishida said.
To achieve this, however, plasters must not contain artificial substances such as glues, he said.
Traditional plastering was supplanted by the prefabricated building methods that were introduced to Japan in the postwar period.
“The (traditional methods) have been re-evaluated in the past five to six years” thanks to public awareness of ecology, Ishida said.
The natural effect is exactly what the owner of the house in Musashino, Tatsuo Koishi, a TV broadcasting company employee, wanted when he asked the Nurikabetai members to give him earthen walls.
“I opted to build my house with concrete to make it quake-resistant. Earth plastering is one thing I can do to make the living space more comfortable and add a natural look and feel (to my house),” he said.
He said the plastering work done by the group, including his friends and acquaintances, also gives the interior a unique appearance. A total of 60 people took part in the project on his house over three days.
Though the finished surfaces by the Nurikabetai group may not be as smooth as those done by professional plasterers, the cost is lower because it basically reflects just the cost of the materials, according to Katayama.
Nurikabetai has worked on more than 60 plastering projects since its inception.
Asked to visit by locals, members went to India to plaster brick walls with local earth materials in 2002 and 2007.
Building owners like Koishi are required to take part in the plastering and organize people who can participate.
So a majority of participants in a Nurikabetai project are novices. Veteran members instruct the others how to mix plasters and apply them to walls.
Naturally the group has experienced some DIY disasters.
“Sometimes earth plaster falls off the walls,” Katayama said.
Getting the timing of the final pudding right is the hardest part, he said. If the timing is wrong the plaster will flake off or crack heavily.
“Our group doesn’t have (established) techniques,” Katayama said. “I have now come to vaguely figure out why we sometimes get flaking.”
The group does repair work when the flaking occurs.
For most people, plastering walls with earth or quicklime is physically demanding.
In addition, the participants come to a project site at their own expense and work for nothing but light meals and drinks served by the owners of the buildings. Despite these conditions, some 200 people have actually participated in the Nurikabetai projects.
“It’s fun to work with people who I met for the first time (on a project site),” said Reiko Murata, a company employee who has been a Nurikabetai member for three years and takes part in some 10 projects a year.
“Earth is a very interesting material. I’m motivated to brush up my skills to plaster (walls) better.”