In the village of Shuanghe, Yunnan, China, the curved gable roof topping the Pinch, a public library and community center, is a hybrid of forms and functions. The wood surface acts as a pedestrian ramp, playground, and seating for people-watching in the neighboring plaza below. It is also a symbol of the rural village’s rise over adversity.
In September 2012, a series of earthquakes struck the southwestern China province, killing more than 80 people and destroying thousands of buildings, including the school and nearly every residence in Shuanghe. As part of its recovery efforts, the government developed a plaza in the heart of the village. Olivier Ottevaere and John Lin, who are respectively an assistant and an associate professor of architecture at the University of Hong Kong (HKU), secured a grant from HKU to design and construct the 80-square-meter (861-square-foot) Pinch.
Located approximately 13 feet below than the village’s primary elevation, the plaza has a concrete retaining wall that Ottevaere and Lin repurpose as a bearing wall for the Pinch. The wall also lets the Pinch’s 123-square-meter (1,324-square-foot) roof become an accessible pedestrian bridge. The surface’s “gentle slope allows people to descend down into the plaza,” Ottevaere says.
The building’s roof, which echoes the shape of the nearby mountains, and three exterior walls are framed in timber as a nod to the traditional houses that once dotted the landscape, before the earthquakes. “We thought, ‘Instead of abandoning this material … why don’t we prove that we can use timber in a modern way?’ ” Ottevaere says.
The team specified birch that had been pressure-treated to resist the elements, fungus, and insect infestations. Trucks transported the wood approximately 250 miles north from Kunming Dianmuju Shangmao Co., a timber mill in Kunming, Yunnan’s capital, to the project site. Local construction crews hand drew the shapes of the Pinch’s 17 roof trusses on the plaza’s concrete floor. These templates were used to construct the trusses from 4.3-inches-wide-by-1.3-inches-thick boards, which are connected with 1-centimeter-diameter, stainless steel bolts. The trusses range in size from 4.9 feet wide by 9.8 feet tall to 19.6 feet square, and are spaced approximately 3 feet apart.
After assembling the trusses on the ground, the crews raised them upright by hand. One end of each truss bears on the concrete retaining wall, while the other rests on one of 17 timber columns. Steel brackets connect the trusses to the retaining wall and the columns, which anchor into the building’s concrete foundation.
Once the trusses were in place, crews nailed 64 3.3-foot-by-6.6-foot aluminum sheets over the trusses and injected silicone sealant in the lap seams. They then screwed 16.4-foot-long, 4.3-inch-by-1.3-inch wood decking, spaced 0.80 inch on center, over the aluminum panels. A 3.6-foot-tall railing traces the plaza-facing roof edge. The railing’s posts align with the columns below, while the rails match the roof decking.
The designers used the modeling software Rhinoceros and physical mock-ups to determine the roof’s three-dimensional geometry, which is created using the straight decking members. The modeling helped assess how much the roof decking could torque between trusses, Ottevaere says. The boards “are buckling in two directions: length and the width,” he says.
Twenty bands of 39-inch-wide polycarbonate corrugated sheets hang from the library’s exterior wood framing. Several sheets act as operable doors and open to the plaza.
Inside the building, the exposed wood structural system serves another essential purpose. Wood bookshelves hang from 13 of the 17 roof trusses, with space around them for circulation. Each bay contains three shelves, approximately 35 inches long and 8 inches deep, that hold approximately 200 books, for a total capacity of 2,400 books.
Fundraising for the project began in September 2012. The project was completed in April 2014 at a cost of 130,000 renminbi (approximately $20,000). Ottevaere says that the Shuanghe community and the children immediately embraced the Pinch. “Once they moved all of their books in, it was theirs,” he says. “[It’s] a monument to the earthquake and the rebuilding effort.”