Signature Theatre, the award-winning showcase famed for its productions of musicals by Stephen Sondheim, is planning to move into a new theater in Shirlington that is nearly four times the size of its current location.

The plans, which are to be unveiled at a news conference and groundbreaking this morning, call for Signature to relocate less than a quarter-mile from its main home in a former automobile bumper-plating factory to a glistening four-story structure at the Village at Shirlington. The current theater has 136 seats in 12,000 square feet of space; the new building will have two theaters with a total of 349 seats and 45,000 square feet.

The project, which is a partnership with Arlington County as part of its innovative Arts Incubator program, will cost $12.5 million and is scheduled to be completed by January 2006.

In its 15-year history, Signature has carved out a niche in the crowded Washington theater scene by doing the unexpected in musical theater, a genre that can be rigidly formulaic. Its funkiness, the catalyst for its engaging and surprising interpretations, definitely extends to the company's building. The staff wants to keep what some consider its charm.

"We wanted to embrace our character and take it with us," says Eric Schaeffer, the artistic director who has led Arlington's first professional theater to 37 Helen Hayes Awards and 176 Hayes nominations since the 1991-92 season. "In designing the building, we didn't want it to be pretentious."

The plan is by VOA Associates Inc., which created the well-received Chicago Shakespeare Theater on the landmark Navy Pier. The new location contrasts sharply with the run-down industrial-strip neighborhood that is now home to the theater. The move will put Signature in an area targeted for round-the-clock vitality that, if all the pieces fall into place, could become as bustling and trendy as Bethesda Row.

The Village at Shirlington, off Interstate 395, is home to public TV and radio stations WETA, a collection of restaurants, a movie complex and another arts enterprise, Classika Theatre. The Animal Welfare League -- the local pound -- is also part of the neighborhood.

In its agreement with the county, Signature is responsible for the interior of the building, and it is almost halfway through a $7 million capital campaign. The county is building the structure and will receive 10 percent of ticket sales for the next 30 years.

Arlington officials predict Signature will be a catalytic anchor for the area.

"We are hoping we can have an entertainment center and make the village function as a 24/7 center," said Barbara Favola, chairman of the Arlington County Board. The county is investing $5.5 million in the building.

Hecht Co. President Frank Guzetta, co-chairman of the campaign, says the theater is working to broaden its base in expectation of increased financial needs. The current budget is $2.6 million, and Signature officials are predicting a $2.8 million budget for 2006. Over the years, season-ticket subscribers have increased from an initial 136 to 4,300. "We are a relatively small theater with a small audience. We have used this building project as a jumping-off point to get more people involved," says Guzetta.

Signature's capital campaign has gone smoothly, raising $3 million so far -- including $1 million each from two philanthropic couples: James A. Johnson, former chairman of Fannie Mae and past chairman of the Kennedy Center board, and his wife, Maxine Isaacs, an adjunct lecturer in public policy at Harvard, who have contributed substantially to the Kennedy Center; and Robert Kogod, a real estate developer, and his wife, Arlene, prime supporters of Woolly Mammoth Theatre and the Clarice Smith Center for the Performing Arts at Maryland. Isaacs, co-chairman of the Signature campaign, says Schaeffer is the selling point. "He is the most gifted young director of musical theater in the country," she says. "I am a firm believer that if you find someone that talented, you should help them."

Right now the Washington fundraising scene is crowded with capital campaigns by local theaters. Arena has set a goal of $100 million; Shakespeare, $77 million; Studio, $12 million; and Woolly Mammoth, $7.5 million. And the Kennedy Center is slated to launch a $250 million campaign.

All these fund drives, Guzetta says, "speak to the growth of the arts. It means there are more people out there with a hunger for it. It is like retailing. You do better when there are more people out there at the mall keeping people excited. But it doesn't make our job any easier."

Managing Director Sam Sweet says that everyone approached for contributions has the same question: Will Eric Schaeffer stay?

Schaeffer, 42, has been the public face and backstage heartbeat of the theater since it was founded in 1989. Signature started as part of Arlington's Arts Incubator project, which gives space and other support to arts groups. After a brief flirtation with moving to downtown Washington, Signature decided that a loyal base of patrons was more important than the incentives developers offered. The company stayed modest, mounting five productions a year and, after its initial year of only serious plays, moved into a mix of offerings. Musicals eventually became its signature, so to speak. Sondheim has agreed to be the honorary chairman for the new building drive, and the new theater will open with a revival of his "Into the Woods."

In addition to his work at Signature, Schaeffer has taken on other highly visible projects, working on Broadway and London's West End. He was the artistic director for the Sondheim Celebration at the Kennedy Center, one of the most successful ventures in the center's history. "There are still things I want to do that we haven't done. There is nothing more challenging than doing a $6 million production somewhere and coming back and doing a $300,000 musical. It takes different brain cells," says Schaeffer.

In the new space, Schaeffer pledges to reach for untested works. At the same time, he acknowledges, "we will do the warhorses. We will invent and we will reinvent." This season the theater has three world premieres: "One Red Flower," a musical about the Vietnam War, has opened, to be followed by "The Highest Yellow," a musical from Tony-nominated composer Michael John LaChiusa, and "Fallen From Proust," a comedy by Norman Allen.

Signature will anchor a building at the end of South 28th Street and will share its space with a county library branch. The box office will be at street level, as will the library. Then theater patrons and staff will ascend to the lobby level on a grand staircase that uses an industrial metal aesthetic to evoke Signature's roots.

It is "a Signature Theatre version with a chandelier that has a brushed aluminum dome and is painted orange inside," says Sweet. "We want to continue creating that sense of surprise and discovery."

Both theaters are black boxes, a performance space with black walls, a flat floor and movable seats. A versatile room, it can accommodate different stages to fit the performance.

Adjacent to the building will be a 750-space parking garage. It's going to be free, something neither the Shakespeare Theatre nor the Kennedy Center can boast. Out front will be a 9,500-square-foot plaza that will connect the new building with the rest of the Shirlington development.

Unfortunately, when Signature moves, its operators will no longer be able to offer their hilarious and singular directions. For years they have told patrons to turn onto Four Mile Run Drive -- and the Weenie Beenie will be on your left.

A rendering of the building that will house Signature's new two-theater complex in the Village at Shirlington.The complex, scheduled to open in January 2006, will give Signature nearly four times the space it has now.