The roofing-related materials appear in the annex to the motor-vehicle proclamation, which the administration issued in response to Canada’s treatment of U.S. automobile exports. Covered goods will face the additional duty even when they otherwise qualify for preferential treatment under the U.S.-Mexico-Canada Agreement. The tariffs apply to goods entered for consumption, or withdrawn from a warehouse for consumption, on or after 12:01 a.m. Eastern time Aug. 19.

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

Depending on their eight-digit Harmonized Tariff Schedule classifications, the affected goods could include some roof coatings and primers, flashing or seam tapes, membrane or underlayment materials, reinforcement fabrics and paper-faced gypsum cover boards. Certain wood panels potentially used for decking or sheathing also are listed, although the annex does not cover every type of structural panel.

The principal tariff classifications for asphalt roofing articles do not appear in the annex, meaning asphalt shingles and conventional asphalt roll roofing do not appear to be covered by the new duties. The motor-vehicle proclamation also excludes articles already subject to tariffs under Section 232 of the Trade Expansion Act. Section 232 is a separate national-security trade authority that has been used to impose tariffs on specified steel, aluminum, copper, timber, lumber and derivative products.

As a result, the additional Section 338 tariff would not be stacked onto an imported article already subject to Section 232 duties. That does not mean all metal roofing, flashing, fasteners or wood products are automatically exempt; coverage depends on the specific product and its tariff classification.

Construction attorney Trent Cotney, a partner with Adams and Reese, said Portland cement stood out among the construction-related products listed. He cautioned contractors not to assume every construction material imported from Canada will be affected.

For contractors preparing new 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 that permit 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 notify the owner or design professional if the tariffs could affect material pricing or availability, Cotney said. Whether contractors can recover the additional expense will depend on the terms of each agreement.

“The industry depends on stability,” Cotney said, particularly in commercial construction, where contractors may submit bids months before work begins and remain on projects for years.

Cotney expects additional negotiations, product carve-outs or a scaling back of the tariffs before the effective date. However, he advised contractors to prepare as though the duties will take effect.

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

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