Building PDX’s wooden roof, from forest to frame

Published June 16, 2022

Sketch of the new roofline

When ZGF Architects presented us with a proposal to build a 9-acre wooden roof over PDX’s new main terminal, we responded with a question: Can we source all this wood in a way that is better for the land and better for our local communities?

Together, the team came up with a set of goals: 

  1. All the wood would come from sustainably managed forests in Oregon and Washington. 

  2. With equity in mind, we should source from small landowners, community forests, and tribal lands all over the region. 

  3. Just like “farm to table” cuisine, we should trace as much of the wood as possible all the way from forest to frame.

No one—in the United States, in fact!—had ever done this before at the same scale. It took two years and many, many phone calls to build a network of foresters, mill owners, brokers, truckers, and construction firms who could join our quest to supply forest-to-frame timber. Here’s how we did it:

Traditionally, timber mills contract with forest landowners to clear-cut timber from large tracts of land. (The landowners also plant saplings to replace the 30-to-80-year-old trees they harvest.) Mills get logs from dozens of forests, and all of that timber goes into massive piles before it’s cut into boards and dried in kilns. 

The system is efficient. There’s little waste. However, by the time the lumber leaves the mill, there's no way to tell which forest it came from.

forest scene being clearcut
close-up image of the lattice

For PDX’s roof, we forged new links in the supply chain so we could source all the wood from sustainably managed forests in Oregon and Washington.

The caretakers of these 13 forests thinned their trees with precision-cutting machines or cleared small (1- to 6-acre) plots. Both methods give the remaining trees better access to water and light, increase biodiversity, and make the forests more resistant to wildfire and drought.

precision loggers thinning a forest

mill with big pile of logs and one tiny (source-identified) plot

The mills that bought these logs agreed to store and cut the wood separately from the rest of their supply—no small effort for efficient, fast-moving operations. Truckers then brought the boards to PDX’s fabricator and construction partners, who carefully labeled and stored all the wood destined for PDX’s roof and made sure it never mingled with other materials.

When the ceiling lattice is installed later this year, we’ll be able to point to specific beams and tell you which forest they came from. We are grateful to the hundreds of people who cared for this wood every step of the way—from forest to frame.

mill with big pile of logs and one tiny (source-identified) plot

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