CALHOUN, GA — Mohawk Industries Inc. has agreed to buy four manufacturing plants for wood flooring from Columbia Forest products. The deal includes two pre-finished solid flooring plants and one engineered wood plant in the United States; the fourth plant purchased is an engineered wood plant in Malaysia. The four plants currently represent $180 million in annual sales. Mohawk said the deal is expected to close in the third quarter and will add to earnings after the first of the year.