DAYTON, OHIO -- DAP Inc., one of the nation's largest producers of caulking compounds and sealants for home construction and maintenance, has been sold to USG Industries Inc. of Chicago for $123 million.

It is the second time in four years that DAP, which has operations in Baltimore, has changed hands.

DAP, which has its headquarters in Tipp City, Ohio, was sold by Beecham Group PLC of Britain, which bought the business in 1983 from Schering-Plough Corp.

USG Corp., USG Industries' parent company, said acquisition of DAP is part of its strategic plan to expand into the repair and remodeling market. About 70 percent of DAP sales are in the repair market. USG formerly was known as U.S. Gypsum Corp.

Altogether, the company has 750 employes. In addition to Baltimore, DAP has operations in Dayton; Lithonia, Ga.; Dallas; and San Jose and Santa Fe Springs, Calif.

DAP had sales in 1986 of $131 million and a pretax profit of $12 million.

When the company was sold in 1983, the price was $75 million. Since then, DAP acquired Roberts Consolidated, a maker of wood preservatives including Weldwood brand products, for $80 million. DAP also divested itself of its floor covering division.

USG Industries said DAP will be grouped with its Durabond Division, which makes adhesives and wall compound.