Above all, the Owens didn't want to live in a box.

Their dream house in Fairfax County had to be exceptional, a one-of-a-kind distillation of their life style and taste; a personal signature. It would have a deep wraparound porch, cedar siding, Palladian windows, a spacious family room.

With that in mind, they bought a verdant five-acre tract near Clifton, hired local architects who came highly recommended, and -- $400,000 later -- made their dream come true. When they moved into the spacious Victorian house in November 1984, they could not have been more pleased.

A year later, their dream of achieving a measure of individuality amid the suburban stock of mass-produced housing was dashed.

Sonja C. Owen, 37, contends that she was driving two miles from her house Nov. 20 when she saw a house under construction that looked startlingly like hers. When she walked onto the five-acre lot and asked to see a copy of the blueprints for the house, she was shown the plans for her own one-of-a-kind dream house, according to a lawsuit the Owens filed recently.

Not quite literally, the Owens hit the roof.

"I think irate would be a light word to use," said Samuel J. Owen, 38. "He followed my plans closer than I did."

Their architects, belying the axiom that imitation is the sincerest form of flattery, also were incensed. "How would you feel if you bought a work of art and you were driving down the street and saw another work of art just like your Michelangelo?" said Wayne N. Topping, one of the architects. In Sonja Owen's worst fears, Topping said, "She was seeing Levittown."

Last month, the Owens filed a lawsuit in federal court in Alexandria, complaining, among other things, that the owner of the second house and several of his associates had violated copyright, civil fraud and misappropriation laws. The Owens, who were joined in the suit by their architects, seek $700,000 in punitive and compensatory damages. What they really want, they say, is for the similar house to be significantly altered or torn down.

Before that happens, though, they seem sure to face a tough legal fight in a case that may be clouded by conflicting laws and their opponent's argument that uniqueness is in short supply when it comes to suburban houses, even in the affluent outskirts of Washington.

The owner of the similar house, which is about half completed, is John Rentz, the president of a small Northern Virginia building company, who had planned to use the house as his own.

Rentz will not say who gave him the Owens' plans. "It came to us simply from a subcontractor in the trade," he said.

He concedes that photocopies of the Owens' plans were "erroneously" submitted by his assistant to Fairfax County's building permit division last May, but he contends that his house is not being built from those plans, despite the apparent similarities.

The plans, he said, were filed and forgotten after they were approved by Fairfax County, and his house is being built from "substantially different" plans drawn up last spring by First Colony Homes, a firm based in Calverton, Va., that is also a defendant in the lawsuit. Earl Collins, a representative of First Colony, refused to comment on the case.

Rentz also denies the Owens' assertion that their blueprints were ever at the construction site of his house.

Rentz maintains that there was nothing unique about the Owens' house in the first place. In an interview last week, the 41-year-old builder took five color photos from a briefcase and fanned them out on a table. One of the photos was of the Owens' house, and each of the others showed a similar Victorian style house in Northern Virginia with a wraparound porch and a connected two-car garage. To a layman's eye, they appeared to be variations on an architectural theme.

"Gee whiz," he said, "no one can claim uniqueness of architectural style . . . . The Owens' home is a subdivision home whose architectural style has been built all over Fairfax County and suburban Maryland.

"This is something that happens all the time. Builders look at other builders' plans. It's a frequent thing."

Each house, Rentz maintains, was inspired by a model popularized in this area by Fairfield Homes, a Northern Virginia company that is one of the largest house builders in the metropolitan area.

The Fairfield model, called the "Bayport 7," was designed by the president of Fairfield Homes, John V. Neill, and his company has been building them since 1981. The model, which is smaller than the Owens' house, sells for $170,000 to $230,000, depending on its location, Neill said.

Neill said that although the house has been widely copied, he decided on the advice of his lawyer not to take legal action against the imitators. "There's not too much in architecture that's sacred," Neill said. "Our houses are so widely copied that it's absolutely unbelievable, and it's very disconcerting. But I finally just closed it."

The Owens charge that Rentz, who has submitted the new First Colony plans to Fairfax County's building permit office, is trying to cover up what they consider to be his theft of their blueprints. They say Rentz is altering his house in midconstruction. Rentz says any changes are unrelated to the Owens' allegations.

Topping, the Owens' architect, and his former partner, Donald F. Crigler, contend that they have been jeopardized financially by Rentz's house because they are liable for their architectural plans.

Rentz said he has decided that he will not live in the Clifton house when it is finished, no matter how the lawsuit comes out. The house is listed for sale at $365,000.

"This is something that's been discussed far and wide in Clifton," he said. "The reason you build something on a five-acre lot is for privacy . . . . Under the circumstances, that might be difficult."