Plywood, metal, and glue go back a long way in the building industry. But they can always be pushed further, as demonstrated by the project that debuted in March 2011: the new Metropol Parasol in Seville, Spain, designed by Berlin-based Jürgen Mayer H. and engineered by Arup. Discard assumptions about how laminated wood pieces fit together, how they are shaped, how they are coated, and how large a structure they can create—and the possibilities open up.
Structural and material engineering did not drive the Parasol until later in its development. Most important to the 2004 competition-winning entry was the spatial configuration and sectional layering that makes the Metropol Parasol at once a shading canopy and elevated plaza, but also a farmers market, restaurant, shopping arcade, roof promenade, and archaeological museum—all while breaking ground in only six spots so as not to disturb ancient Roman ruins below. This is a machine for revitalizing public space in the heart of the old city.
But how to actually construct this exuberant civic monument? Steel was considered as a building material, as was fiber-reinforced concrete, and wood both with and without a weatherproof coating. Cost, fire performance, and the effects of expansion and contraction under the fierce Mediterranean sun were all parameters for the design. Ultimately, the Parasol structure was designed as a square waffle-grid system of interlocking, CNC-milled timber fastened with steel connectors and high-strength glue. The wood itself is laminated Kerto-Q LVL, manufactured by Finnforest in Aichach, Germany, in sheets measuring approximately 131 by 7 feet. It has a clear polyurethane coating that is fully weatherproof, yet elastic and breathable, just like the sculpted columns of a college canteen that Mayer designed in Karlsruhe, Germany.
The Metropol Parasol is the world’s largest building to be held together primarily by glue. This long-spanning structure measures up to 492 feet long, 246 feet wide, and 92 feet high. The glue—a new formula developed by the Fraunhofer Institute, according to Mayer—hardens inside the custom-engineered joints where steel connectors penetrate the wood. The 3,000 or so conjoined segments (with about 40,000 connection points) were preassembled off site, then tempered to increase the glue’s heat-resistance to about 176 degrees.
The Parasol’s free-sculpted form may evoke Joan Miró (the Catalan painter), or perhaps the undulating vaulting of Seville’s cathedral. Yet any number of such references pale in comparison to the forceful presence of this building in itself, which spreads its aqueous geometries over the Plaza de la EncarnaciÓn like a hovering pond in the middle of Spain’s hottest city.
The overall typology of the Parasol is matched by the constant differentiation of individual wood shapes and ply thicknesses, the latter optimized via digital modeling for lightness and strength. (More glue equals stronger.) “When you’re up there you can see how the material jumps from one thickness to another,” Mayer says. That is, if you’re not too busy taking in the sweeping views of Seville.