Raleighs Store Corp. said yesterday it sold its flagship store at 1133 Connecticut Ave. NW for $7.5 milion to a development group that plans to put up a 12-story building including a new, smaller Raleighs outlet.

Raleighs said it agreed on July 3 to sell the property, but would not identify the buyer of the 15-year-old building and 7,538-square-foot plot of land. No record of the transaction is on file with the District. There is no legal requirement for promptly filing transactions with the city, although most are filed within three days, according to industry sources.

Raleighs said it will move its downtown store to a new unoccupied office building across the street at 1130 Connecticut Ave. NW on Feb. 1. The building Raleighs now occupies will be razed.

When the new building is finished in late 1988, Raleighs will move into the first three floors. The current store has about 23,000 square feet of retail display space spread over six floors, but more efficient design will allow nearly the same selling area on three floors, said David Nellis, vice president of sales promotion.

President Neil J. Fox said the new store will have about the same amount of street frontage, with display windows on Connecticut Avenue and DeSales Street.

Raleighs' temporary location will have only 12,000 to 14,000 square feet of sales area and will "cause some sense of disruption for some customers," Fox said.

He said the temporary store would be "a bit more spartan than the Raleighs customer appreciates," but that service would be uninterrupted.

"We will be smaller without being diminished," Nellis said. "Where we'd normally have, say, 20 Hart, Schaffner & Marx brown suits, size 42-regular, we'll only have 10."

The downtown Raleighs underwent a $200,000 remodeling when the chain was purchased by Fox, a former Neiman-Marcus executive, and a group of investors in 1984.

Raleighs, which was founded in 1911, also has stores at Mazza Gallerie, White Flint mall, Wheaton Plaza, Lakeforest Mall, Prince George's Plaza, Landover Mall, Tyson's Corner, Fair Oaks mall, Springfield Mall and Montgomery Mall.