Home Depot's push into the pro market began in earnest last year, when the company dropped $18.5 billion to buy SRS Distribution.

Home Depot has entered an agreement to buy GMS INC for about $4.3 billion, a leading specialty building products distributor on Monday.

Home Depot bought SRS Distribution — the subsidiary that’s acquiring GMS — last year for $18.25 billion, in the largest acquisition in its history. Texas-based SRS sells supplies to professionals in the landscaping, roofing and pool businesses and it has bought up many other smaller suppliers as it’s grown.