President Donald Trump has made housing affordability a defining commitment of his second term by moving aggressively to build more housing: faster permitting, federal land for development, and sustained pressure on state and local governments to dismantle the zoning restrictions that have throttled supply for a generation. If these efforts succeed — and there is real reason to believe they will — America could see its fastest expansion in homebuilding in decades.

But a significant blind spot remains, and it deserves more attention. For decades, the United States has imposed import tariffs on Canadian softwood lumber, constraining supply, and raising prices, in the U.S. As the Trump housing boom begins, there is a real concern that there may not be enough affordable building materials — particularly lumber — to build.