The construction-related materials appear in the annex to the motor-vehicle proclamation. Covered goods will face the additional tariff even when they otherwise qualify for preferential treatment under the United States-Mexico-Canada Agreement.

The annex includes Portland cement other than white cement; certain nonaqueous polymer-based paints and coatings; self-adhesive plastic sheets and films; nonwoven materials; coated or impregnated fabrics; paper-faced gypsum boards and panels; and selected particleboard, fiberboard and plywood classifications.

Depending on their eight-digit Harmonized Tariff Schedule classifications, affected products could include some cementitious materials, coatings and primers, flashing or transition tapes, air- and water-barrier components, reinforcement fabrics, paper-faced gypsum panels and wood substrates.

The listings do not mean every product within those broader categories will be subject to the tariff. Importers and contractors will need to confirm each product’s tariff classification and country of origin.

Paper-faced gypsum boards and panels are especially relevant to the wall and ceiling industry. However, the listed classification does not automatically cover every type of gypsum board, shaft liner, sheathing panel or specialty cover board imported from Canada.

Portland cement also could affect contractors performing plaster, stucco, masonry and other cementitious work. The proclamation specifies Portland cement other than white cement, meaning product coverage will depend on the material’s composition and classification.

The proclamation excludes articles already subject to tariffs under Section 232 of the Trade Expansion Act. Section 232 is a separate national-security trade authority covering specified steel, aluminum, copper, timber, lumber and derivative products.

As a result, the new 50% Section 338 tariff would not be added to an imported article already subject to Section 232 duties. That does not mean all steel framing, metal lath, accessories, fasteners or wood products are exempt; the treatment depends on the classification of the specific imported article.

Construction attorney Trent Cotney, a partner with Adams and Reese, said Portland cement stood out among the construction materials listed. He cautioned contractors not to assume that every Canadian construction product will be affected.

For contractors preparing bids, Cotney recommends including price-escalation provisions that allow contract adjustments when material costs increase beyond an established threshold. He also recommends material-substitution clauses permitting contractors to propose domestic or alternative products when specified Canadian materials become unavailable or prohibitively expensive.

Contractors working under existing agreements should review their contract language and promptly notify the owner, general contractor or design professional if tariffs could affect material prices or availability, Cotney said. Whether a contractor can recover the additional cost will depend on the terms of the agreement.

“The industry depends on stability,” Cotney said, noting that commercial contractors often submit bids months before materials are purchased and may remain on projects for years.

Cotney said negotiations, product carve-outs or other changes could narrow the tariffs before they take effect. However, he advised contractors to prepare as though the duties will be implemented.

“Be proactive, stay prepared, watch your contracts, and make sure you’re addressing it on bid docs,” he said.

Manufacturers, distributors and contractors should confirm the eight-digit HTS classifications of Canadian products with suppliers, customs brokers or trade advisers before determining whether a material is covered.