A second group of neighbors in Arlington's Courtlands area has reached an agreement with a developer to sell their houses as one package for prices that are at least twice what county officials estimate the properties would bring if they were sold individually.

The owners of 13 properties near the Court House Metro station signed sales contracts this month with the Dittmar Co., which plans to tear down the houses and build apartments, said Clive R. Richmond, a spokesman for the homeowners. The deal is expected to go to settlement in the fall.

Dittmar, based in Vienna, is proposing to pay about $9.5 million for 15 properties, said Richmond. The owners of two properties have not reached an agreement with the developer, he said.

Most of the properties are in the south end of a large block bordered by North 14th Street, North Wayne Street, North Veitch Street and Fairfax Drive. Four other houses in the package are on the other side of Veitch Street. The area contains mostly modest, half-century old, single-family brick or wood frame houses.

Richmond declined to reveal the precise sales price but said homeowners would receive more than the $60 a square foot recently paid to another group of Courtlands residents, who concluded a deal last month in which the Moyarta Corp. of Virginia paid almost $20 million to 30 property owners.

Dittmar gave the Courtlands neighbors $360,000 in earnest money this week to demonstrate its good faith. The money was distributed according to lot size, and the homeowners can keep the money if the deal falls through, said Richmond.

Christopher A. Brigham, a spokesman for Sidney E. Albrittain, one of the owners of Dittmar, confirmed that the company is buying the Courtlands properties but declined futher comment. Albrittain's "position is extremely low-key," said Brigham.

In choosing Dittmar, the homeowners turned down other major developers such as Trammell Crow, said Richmond.

Dittmar offered the best price but also has a track record in Arlington, he said. The firm has built an apartment complex on North Barton Street in the Courtlands neighborhood. "He's a builder, a definite builder," Richmond said of Albrittain.

Richmond and his neighbors had previously negotiated a deal with Alexandria developer Robert M. Stein and Associates but it fell through in December 1986. Several lawsuits concerning the Stein deal are pending in Arlington Circuit Court.

"We were all very embarrassed by what happened the first time," said Richmond. "We felt a responsibility to sell to someone who would come in . . . and build."