Wood construction has typically been used for purely residential products in the past few decades and especially after fire protection standards became more stringent. Besides fire rating, concrete and metal has several other benefits over wood, including overall strength, resistance to insects, and resistance to rot. Wood, however, does have some advantages over concrete and steel, like its relative light weight and it’s much less harmful to the environment.
In Hillsboro, Oregon, general contractor Swinerton Builders is a few months into the construction of the new First Tech Federal Credit Union, which is believed to be the largest mass timber building in the United States by building area.
Mass timber is not your standard wood stud and OSB sheathing structure. Rather, it’s structural components are comprised of much more substantial cross-laminated timber (CLT), nail laminated timber (NLT), dowel-laminated timber (DLT), or glue laminated timber (glulam).
The new building in Hillsboro is made up of glulam posts and beams, which are parallel lumber structures that have been joined together with moisture resistant glue. The flooring is made of CLT (pictured above in main image), which are stacks of lumber, with each layer running perpendicular to the layers above and below. CLT has a high compressive strength, which makes it a great option for flooring.
The new headquarters for the credit union will stand 5 stories high and cover 156,000 square feet in total. Below you’ll see a short video of the first CLT floor panel being hoisted by a crane:
Many building departments around the country have been wary of approving mass timber products, especially after other major wood projects have created 5 alarm fires in recent years. Proponents of mass timber projects hope to show that CLT, glulam, and the other laminated wood structures are much safer than lightweight wood construction.
When starting a bonfire, you would never start with a large, solid piece of wood, right? You’d reach for the small chips and other products easy to ignite.
More: Nation’s largest ‘mass timber’ building under construction in Oregon | Capital Press