Home Depot on Tuesday cautioned it was difficult to predict how its business would be impacted by a potential change in shopping habits in the coming months as the reopening of the U.S. economy threatens to slow a pandemic-fueled sales boom. The lack of a solid forecast from the top U.S. home improvement retailer, which benefited in the last year from a strengthening housing market, came as data showed homebuilding fell more than expected in April, likely pulled down by soaring prices for lumber and other materials. Supply shortages and surging demand have caused lumber prices to more than triple in the past year, helping buoy sales at Home Depot but hitting its margins. The company’s same-store sales jumped 31 percent in the first quarter, while higher lumber prices alone hit gross margins by about 35 basis points. A fresh round of government stimulus checks in March also added to …