Buyers of Canadian softwood lumber are not paying one tariff. They are paying two, and the two do not offset each other. A 10 percent duty imposed under Section 232 of the Trade Expansion Act of 1962 has applied to nearly all softwood lumber and timber imports since October 14, 2025, and it sits directly on top of the antidumping and countervailing duties Commerce has assessed on Canadian lumber for decades. Neither the White House proclamation that created the Section 232 duty nor the U.S. Customs and Border Protection (CBP) guidance implementing it treats the two regimes as interchangeable. They stack.
That stacking is no longer theoretical. Martin Wiegand, who runs a Washington, D.C. lumber wholesaler that has sold Canadian western red cedar since the 1800s, told CTV News this week that a 2×4 he bought for roughly $9.50 a year ago now costs him about $16. More than half his volume is Canadian cedar, and he says the combination of duties has made inventory planning close to impossible. His business is small, but the mechanism behind his invoice is the same one every framing lumber importer, distributor, and specifier is now working through.
Two tariff regimes, one invoice
The Section 232 duty and the antidumping and countervailing duty (AD/CVD) orders on Canadian softwood lumber come from entirely different legal authorities and were built for different purposes. The AD/CVD orders, in place in some form since 1982, address a finding that Canadian producers sell lumber in the United States below fair value and benefit from subsidized stumpage. Section 232, by contrast, rests on a Commerce Department finding that import volumes of timber, lumber, and derivative wood products threaten national security, the same statute used for steel and aluminum tariffs.
Because the two rest on separate statutory findings, U.S. trade law does not require CBP to pick one. Legal guidance from trade counsel following the September 2025 proclamation was explicit on this point: existing antidumping and countervailing duties “continue to apply in addition to the Section 232 duties,” a treatment the proclamation itself confirmed and CBP’s implementing guidance carried into the Chapter 99 tariff provisions importers now use to file entries. Softwood lumber entries fall under heading 9903.76.01, covering 14 subheadings within HTS chapters 4403 and 4407, and CBP has not published any offset or credit mechanism against AD/CVD cash deposits.
What the numbers actually show
The AD/CVD side of the ledger has moved this year, and the direction cuts against the stacking story only on paper. In preliminary results published April 14, 2026, covering the 2024 review period, Commerce calculated antidumping margins of 16.85 percent for Canfor Corporation, 13.25 percent for Resolute Forest Products, 4.77 percent for West Fraser Timber, and 10.66 percent for non-selected companies, down from the prior review. Commerce had originally set a 120-day clock for final results, which would have landed in mid-August, but the agency has since extended that deadline. Add the countervailing duty rate, which moves separately, and the combined AD/CVD burden for most Canadian shippers still lands in the mid-20s to low-30s percent range before the Section 232 duty is even applied.
That is the arithmetic Wiegand is living with. A 10 percent Section 232 duty added to an AD/CVD rate in that range pushes the effective combined burden on a given shipment toward, and in some cases past, 35 percent, a level the U.S. Lumber Coalition and Canadian producers have each cited independently this year, from opposite sides of the argument, as the real number buyers are transacting against.
Commerce is still finding new companies to add
The AD/CVD order is not static even at the margins. On August 6, 2026, Commerce published amended final countervailing duty results reinstating Les Produits Forestiers D&G Ltée and Les Produits Forestiers Portbec Ltée into the CVD order after the U.S. Court of International Trade, in a July 21, 2026 judgment, sustained a recalculated subsidy rate of 1.05 percent for the two companies, above the de minimis threshold that had excluded them since 2019. CBP began collecting cash deposits from the two Quebec-based companies at that rate for entries made on or after August 6. It is a small dollar figure next to the Section 232 duty, but it illustrates that the antidumping and countervailing duty order is a living document, subject to litigation and recalculation years after entries are made, at the same time an entirely separate tariff is layered on top of it.
Downstream pressure and a diversification response
The National Association of Home Builders (NAHB) has pressed the administration on the compounding effect since the Section 232 proclamation, noting that the United States imports roughly one-third of the softwood lumber it consumes, that Canada supplies close to 85 percent of those imports, and that domestic sawmills are running at only about 64 percent of capacity, not enough to absorb the gap on short notice. NAHB has asked Washington to pursue a negotiated resolution rather than additional restrictions, arguing the tariffs raise the cost of new construction at a time affordability is already strained.
Canadian producers are responding by diversifying away from the U.S. market rather than waiting for a settlement. Statistics compiled by Canadian trade authorities show the U.S. share of Canada’s softwood lumber exports has fallen to roughly 89 percent in the first half of 2026, down from historical norms in the mid-90s, as mills route more volume to Japan, China, and other Asia-Pacific buyers. That shift matters for U.S. specifiers and distributors because it changes who has pricing leverage in the next round of negotiations, and it is a trend line worth tracking independent of where the AD/CVD final results land.
What to watch
Three dates matter most through year-end. Commerce’s delayed final antidumping determination for the 2024 review period will reset cash deposit rates once it publishes, and importers should expect retroactive assessment adjustments tied to it. A January 2026 proclamation already pushed the scheduled increase in Section 232 rates on upholstered furniture and kitchen cabinets from January 1, 2026 to January 1, 2027, with an exemption path for countries that reach agreements addressing the underlying national security finding, a path Canada has not yet used for lumber itself. And CBP’s Chapter 99 filing codes are worth rechecking each quarter, since amendments to the September 2025 proclamation have already changed HTS classifications once. Buyers modeling landed cost for the fourth quarter should treat the Section 232 duty and the AD/CVD rate as two separate, additive line items, not as alternative measures of the same trade dispute, because that is exactly how CBP is collecting them.