Caught in a bruising preservation battle, members of the Third Church of Christ, Scientist and developers who want to add an office tower next door to the "Brutalist"-style church at 16th and I streets downtown are vowing to fight a decision to designate the structure as historic.

The nature of the appeal is uncertain, but lawyers for both the church and ICG Properties said they may ask the mayor's agent for historic preservation to allow demolition despite the landmark designation, if they can convince him their replacement project has the required "special merit." There is also talk of a court appeal on constitutional and religious-freedom grounds.

Members of the church, saddled with a dwindling congregation and what they consider a dysfunctional building, want to tear it down and build a smaller "purpose-built church" using funds from the proposed office development.

But the Historic Preservation Review Board, in one of the most hotly fought cases in recent memory, voted 7-0 Thursday to designate the octagonal church and adjoining Christian Science Monitor building as a local landmark. Board members agreed with their staff that the complex as a whole is an "outstanding" example of Brutalism, a mid-20th-century style that features angular or blocky walls and forms composed from roughly cast concrete.

"It's an outstanding work of modernist architecture and of ecclesiastical architecture," said board chair Tersh Boasberg, noting that dozens of prominent architects and architectural historians wrote in support of the nomination. "There was not a single piece of evidence to the contrary."

Boasberg also said there are "design solutions" that would allow the congregation to remain on the site, perhaps in part of a modified office building, even if the church itself is landmarked.

Designed by Araldo Cossutta of I.M. Pei's renowned architectural firm, the Christian Science complex and its plaza were constructed in 1971. A landmark application by the Committee of 100 on the Federal City and D.C. Preservation League has been pending since 1991, putting the church's goal of a new building on hold.

ICG's redevelopment plan, and pending demolition permit, finally forced a hearing this fall. The company, which now owns the entire site, wants to build a new office tower at 16th and K streets, retain

some of the open plaza, and build a "newly designed and environmentally sensitive" home for the church, an ICG official said.

Because of the prickly issues in the case, the preservation board held an initial hearing in November, then a site visit, and then a final hearing last week. An unusually large and tense crowd waited impatiently for Thursday's meeting, while board members trickled in because of a Metro snafu, and waited again while staff tried to fix a faulty sound system.

When the hearing finally got under way, chair Boasberg cautioned witnesses: "We're not here to discuss the First Amendment. ... The only issue is whether the building meets criteria" for landmark protection.

Richard Longstreth, a professor of architectural history who argued for the landmark application, said questions raised about whether Cossutta or Pei was the leading architect, or whether the building is Brutalist or just modern, are "largely beside the point."

"The design is what matters," said Longstreth, who testified that the design compares favorably with other modern churches around the country. "The Third Church is an outstanding example of modernism," he said.

Longstreth also argued that in Washington and other cities, churches with dwindling congregations have partnered with private firms to preserve their buildings and add other uses. "Working with the National Trust, the Third Church can keep its congregation intact and flourish."

Staff architectural historian Tim Dennée read from the church's own visitors guide, which describes a "small, jewel-like church" with "pleasing proportions" and an exterior carillon of 20 bells. Dennée quoted Cossutta himself explaining the design: " ... a unified visual image, an energetic affirmation of structure, stripped of all excuse."

Arguing for the developer, attorney Whayne Quin said the complex neither carries out Cossuta's original design nor meets the needs of the church. Noting that lower 16th Street was recently designated a historic district, Quin said, "If they sought to build it today, it would not be approved by this board."

"Its architectural deficiencies burden our practice," said Darrow Kirkpatrick, an engineer and longtime congregant. He described an "HVAC system beyond its usable life, the absence of windows, two ineffective skylights and moisture that penetrates through uninsulated walls."

"Even with unlimited finances, there's no feasible way to fix it," Kirkpatrick testified. Landmarking, he said, "would be considered `constructive eviction.'"

New member of the church Amy Meyers said the small downtown congregation now ranges from "senior government officials to homeless." But the hidden entrance is unwelcoming to visitors, and the chill and hum of fluorescent lighting make worship difficult, she said.

Meyers paused, fighting back tears. "Christians worship God, not edifices," she said, quoting Mary Baker Eddy, founder of the Church of Christ, Scientist. "The building should serve the church, not the other way around."

The Becket Fund for Religious Liberty has raised constitutional issues. The fund, in a letter, said landmarking might make the congregation unable to stay in the building, thus placing an "undue burden" on its religious exercise.

Ward 2 Council member Jack Evans, who had supported the original landmark application, wrote the board last week to express his strong opposition, noting that "the strength of this grand avenue is weakened by the existing bunker-like concrete structures" and that a landmark designation could "force the Church to move its congregation out of the District."

Board members said they did not see Evans' new letter, filed two days before the hearing, and some said they assumed the council member still supported landmarking.

After the vote, Dupont Circle advisory neighborhood commissioner Mike Silverstein vowed that the commission will "fight the landmarking until it is overturned. It's their church and their fight, but we will support them in every way we can," he stated in an e-mail to The Current, also warning that the "battle could have unpredictable consequence for historic preservation efforts in the city."

There are three possible avenues of appeal:

o ICG and the church could appeal the landmarking decision to D.C. Superior Court, but they would prevail only if they can prove the board's decision was arbitrary, capricious or unlawful.

o They could appeal to the mayor's agent, an administrative law judge, to allow demolition if they can prove their replacement project has "special merit" or that the landmark constitutes a "taking," leaving no economic use for the property.

o They could go to federal court and argue the decision puts an "undue burden" on the church, under the Constitution or under a 2000 law limiting government restrictions on "religious land use."

One observer noted the last two avenues of appeal are made more problematic because ICG is now the property owner, and the church only a tenant.