Header: Header: Header:

In October, developers will break ground on Framework, a 12-story, 130-foot-tall mixed-use tower in Portland, Ore., designed by local firm Lever Architecture. Fast on its heels is SHoP Architects’ 475 West 18th Street, a 10-story, 120-foot residential tower in the Chelsea neighborhood of Manhattan, which is now awaiting final approval from the city of New York. Even though the two projects are set to become the tallest mass timber towers in the U.S., they represent something even more noteworthy: a break in a fundamental building paradigm.

Hardly any mass timber buildings of any height have been built in this country, despite a wide cross-section of the construction industry—including architects, developers, timber companies, and environmentalists—hailing cross-laminated timber (CLT, comprising several layers of wood planks glued together) as the building material of the future. Indeed, last fall, the two buildings split a $3 million grant from the U.S. Department of Agriculture (USDA) to support the projects’ research and planning phases.

But don’t expect steel and reinforced concrete to disappear from mid- and high-rise construction anytime soon. For all of CLT’s promise, a growing number of skeptics warn that it and other engineered wood products, such as glue-laminated timber, have a long way to go before they become mainstream in America.

“Just in the last four to five years, a global precedent for tall timber has emerged, but it’s only now getting to the U.S.,” says Hans-Erik Blomgren, a structural engineer in Arup’s Seattle office who is working on Framework. Austria has become the epicenter of CLT production, and Europe already has a half-dozen mass timber towers topping six floors, with several taller buildings on the way. Treet, in Bergen, Norway, currently holds the title as the tallest mass timber tower in the world, at 160 feet, and several buildings have recently sprung up in Canada, particularly in Vancouver and other parts of heavily forested British Columbia.

From Architect Magazine: http://www.architectmagazine.com/technology/building-codes-mass-timber-towers-become-a-reality-one-additional-floor-at-a-time_o