From the exterior, Ligne Roset’s complex in Briord, France, is little to look at, just workaday cement- and-metal factories near the base of the Alps. But once you step inside, the operation bursts into colorful life, with dozens of workers hefting gigantic bolts of fabric, manning robotic sewing machines, and operating cartoonish foam cutters and glue sprayers.

The family-owned company has been making furniture in this location for 38 years. On a recent fall afternoon, the cavernous Briord 1 factory was running full throttle, all the workers focused on turning out French designer Inga Sempé’s Ruché sofa, introduced in 2010 and already iconic. The sofa’s simple form—a slim beech frame draped with a cushiony quilt—belies the effort it takes to produce one: ten-and-a-half hours of labor and up to 11 different craftspeople’s hands.

“When you see a finished object, you can rarely imagine all the work that went in to it,” muses Sempé. “All the sleepless nights for the designer, who stays up thinking about just one curve, all the people who built it.” We tour Ligne Roset’s factory to learn just what it takes to make a Ruché.

1. The Frame

Each Ruché is made on demand, and with 35 fabric and leather choices, hundreds of color options, and four frame variations (natural beech or stained red, blue, or gray), the piece is almost endlessly customizable. The frame starts as raw timber housed underneath a corrugated-metal canopy on Ligne Roset’s 15-acre Briord campus. When an order comes in, workers feed the wood into a high-tech preprogrammed machine that mills it into ten square-sided posts and drills holes where the pieces will connect (above, bottom right). A craftsman then assembles the ends of the frame, connecting the pieces using wooden pegs and glue. Next, it’s passed along to a technician in a ventilator mask who sprays the wood with a transparent stain or varnish (above top). Once dry, the frame components, seat, and steel- springed backrest are joined with glue and pegs (above, bottom left), and Velcro and strips of zippers are stapled to the places where the quilted cover will eventually attach.

2. The Foam

In one corner of the 382,000-square-foot factory, stacks of colorful, spongy foam await their fates, each hue indicating a different density and use (top and bottom right). After quick work on the computerized foam cutter, the three pieces of foam that will eventually comprise the backrest travel on a wheeled trolley to the glue booth, a white-walled space resembling a walk-in industrial fridge. A technician sprays a sheet of pliable purple memory foam with a water-based adhesive and then carefully folds it over the other two foam layers and a steel spring grill to complete the backrest (bottom left). All these cushiony layers will be invisible beneath the quilted cover but will immensely improve the sofa’s comfort.

3. The Cover

Ligne Roset is fanatic about fabric quality. Before a bolt is used, workers unroll it completely and inspect it carefully for color variation, nubs and pulls, and other defects. If the quality is suitable, an automated 17-foot-long Gerber Cutter cuts the fabric according to the pattern (above top). The colorful cutouts are piled one stack per sofa and labeled with the future owners’ names and hometowns before they are wheeled to the sewing area, where they meet up with thin sheets of precut batting. Seamstresses layer the fabric and batting and attach them to a frame that temporarily holds the pieces together (above, bottom left). The frame is then inserted into a gigantic preprogrammed sewing machine that quilts the surface with the “broken grid” of lines that Sempé devised to create the cover’s signature texture. It takes an hour and a half for the machine to make its 2,008 stitches, with cold air constantly blowing on the needle to prevent broken threads caused by friction and overheating. Once the quilting is complete, the women remove the cover from the frame, speedily snip off loose threads with scissors, and use an electric cutter to trim it to its final shape. Other sewers then stitch zippers on to the cover’s edges to enable it to attach securely to the wooden sofa frame (above, bottom right).

4. The Final Assembly

“I love to see the different parts from the factory all united at the end,” says Laurence, a small, muscular, ponytailed woman who has the glory job of transforming the various pieces into a finished Ruché, all in about 15 minutes. She starts by carefully arranging a final sheet of foam inside the cover, ensuring it lies flat. Then she drapes the piece over the frame, aligns the seams, attaches the corners and edges with the zippers and Velcro, and then firmly and deliberately places well-calibrated karate chops to the corners. If she needs to, she can consult her quality-control photo, a glamour shot of one single perfect Ruché. After a few additional adjustments, which include hitting the cover with both hands outstretched to “fluff” it, this particular Ruché is ready to ship to Germany. “It’s not an easy model to make,” Laurence says proudly, “but it’s such an interesting one.”

Click here for an extended look at designer Inga Sempe's creative process.

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Ruché Sofa