BofA warns earnings in this corner of the stock market could be headed for a 20% drop because of tariffs

Workers are seen as new construction takes place at the Umbria a Lennar Corp. project on September 19, 2011 in Miami, Florida.

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• Homebuilder materials firms face a 20% hit to EPS from tariffs, BofA says
• Tariffs are bound to lift product prices, adding to housing costs.
• The sector dropped 12% since Trump's unveiled the latest duties on imports last week.

A double-digit earnings hit to American building product companies is on the horizon as tariffs stir up industry headwinds.