Willie Brown, 74, doesn't understand why the Hechinger Company has yet to install his new concrete porch with its white aluminum canopy, replacing the old wooden porch that collapsed last September.

The reason -- the Joint Committee on Landmarks for the Nation's Capital, a group Brown has never heard of, didn't like the awning.

Essie Davis, 67, is not happy with the white aluminum siding just installed on the exterior of her frame house on Sixth Street SE.

"I don't like the siding because it's not what we wanted," she said. "It was just their (the committee's) idea of what they like. Just their idea of what they would like for this house."

The joint committee -- which Davis too, had never heard of -- decided the simulated wood-grain siding she had originally chosen would be unsuitable.

Across town, the Embassy Row Hotel near Dupont Circle envisioned a blue awning outside the hotel to announce its remodeled French restaurant -- Le Consulat. No, said the committee, the awning must be brown.

These three owners' plans were frustrated because their buildings happened to be located in historic districts. The city, by law, cannot issue permits for exterior alterations to the 14,000 buildings in Washington's 14 designated historic districts without consulting the committee first.

The historic districts are Georgetown, the Washington Navy Yard, the U.S. Marine Barricks, Logan Circle, Capitol Hill, Pennsylvania Avenue, Lafayette Square, LeDroit Park, Dupont Circle, 16th Street from Scott Circle to Florida Avenue, Anacostia, the C&O Canal through Georgetown, Gallaudet College and Massachusetts Avenue from 17th Street NW to Observatory Circle NW.

"I felt since it was your house that you should be able to do with it what you want," said Davis, who has lived in her Sixth Street home for 37 years. "I don't know why they would not let you have what you want, but it seems they don't and you take what they give you."

Like Davis, others have discovered that the ninemember group's authority extends to such apparently inconsequential matters as porches, steps, windows and signs.

Last year the committee ruled on 425 cases, ranging from the color of paint on a new outside duct to plans to cover the 100-year-old brick facade of a Capitol Hill church with artificial stone.

"The man at Hechinger's said something about the commission, about having a meeting with them, but I didn't know what he was talking about," said Brown, who works in a laundromat about a block from his home.

"It's a hindrance there is no question about that," said William Satuffer of Hechinger's. "I can understand why they (the committee) do it, but Mr. Brown's porch was falling down and he had no choice but to replace the thing."

"We're trying to preserve a district the way it is or the way it was," said Committee Chairman Henry H. Brylawski, explaining the committee's mission as guardian of the historical and architectural integrity of the designated neighborhoods. "So the question is, does the alteration violate the character of the historic district?" said Brylawski, who practices law in addition to his parttime service with the committee.

According to supporters, historic districts protect the old and picturesque from demolition, and prevent the intrusion of high-rises and incompatible commercial and residential structures.

Opponents say the historic district concept restricts the property rights of owners and discourages development. In addition, some black leaders argue that historic district status leads to the displacement of the poor and black because of the real estate speculation that often follows an organized campaign to preserve a neighborhood's architecture.

Many historic districts, nationally and locally, were once concentrations of large homes for the rich; then the rich moved out, and through the years the houses were handed down to poorer and poorer owners and occupants. Now the middle class is rediscovering the tarnished charm of these big, old houses.

Life in a historic district is not all restrictions. Owners are also eligible for special federal loans and grants to help them pay the extra costs imposed by the historic designation. But there is a little money available under these programs -- only $353,000 was spent in the District this fiscal year -- and strict guidelines for rehabilitation and restoration must be followed.

A more powerful incentive may be the tax provision that allows owners of commercial properties that "contribute to the significance of a historic district" to write off all "certified" rehabilitation expenses over a five-year period.

The 14-year-old joint committee in the District is technically an advisory committee to the city's housing director. But it is extremely rate for the housing director to reverse a committee recommendation.

In December, the D.C. Council passed a tough new bill giving the committee, or a body like it, the authority to deny renovation and demolition permits outright, not simply delay them, unless an owner can show an economic hardship or a compelling public interest to the contrary.

The committee's jurisdiction under the terms of the bill, now awaiting congressional review, would be enlarged to include not only alterations and demolitions but also new construction.

The committee's performance to date has received mixed reviews from those who deal with it regularly.

"I think the concept is a good one," said Steve Cymrot, a Capitol Hill real estate investor. "It tries to maintain certain standards... What I object to, and I object to very strenuously, is that you have a body operating with no regulations. I've been to meetings where one member leans back and says I think it should be bigger,' and another says it should be smaller... I think the nature of the proceedings is an arbitrary one."

But he concluded, "I think they have done more good than bad and they have kept out a lot of junk probably, such as aluminum siding."

"We cannot have a historic district without some form of control over what goes in it," said Armistad Peter III, a Georgetown owner who is renovating a Victorian house on 31st Street NW.

But a three-week delay in approving his plans "drove us into cold weather and the Christmas holidays," he said, and that slowed the construction process.

Both the Landmarks Committee and the Fine Arts Commission, a federally created body of seven, had to review Peter's plans because alterations and demolitions in Georgetown need the approval of both bodies. Peter thinks the process should be speeded up.

Shelley Fisher, owner of the Yummy Yogurt stores, said committee objections to his plans for a new store in the 500 block of 10th Street NW, next to the house where Abraham Lincoln died, will cost him an extra $4,000 to $5,000.

Landmarks committee member Dr. Harold K. Skramstad, conceding that "there is judgment involved" in the committee's decisions, nevertheless argues that "we're doing these people a favor... In the long run their housing will be infinitely more valuable by retaining the historic ambience of the buildings."

"Some of the best architects in the country sit on this panel and people get to benefit from their knowledge," said Tanya Beauchamp, a member of the committee's staff.

Committee meetings resemble collegiate arcitectural seminars. Young architects, hired to redesign residential or commercial building, have their work assessed by the board members in the language of "roof elements," "roof lines," "cornice lines," "matching bricks," "pitched roofs," and "double-hung windows."

"You get the idea of a dog giving birth to a house," Skramstad told one young architect, while scrutinizing a cardboard model of a proposed office building on Capitol Hill's Stanton Park.

"I hate it!" was another board member's concise verdict. The architect was told to restudy the proposal.

"It's kind of scary" for ordinary homeowners, said Suzanne Ganschinietz of the committee staff, "because other people are here with models (and architects)."

"Traditionally, joint committees have been closed clubs," said Robert DeForest, head of the Afro-American Institute for Historic Preservation and Community Development. Historic districts have been "a sophisticated from of de facto segregation" and have "worked to the disadvantage of the disadvantaged," he said.

Architect Louis M. Fry Jr., one of two black members of the Landmarks Committee, disagrees. "We have bent to recognize hardship," he said, and "the economic burden we have caused has been minuscule."

"The movement back to the city of whites, that movement is an economic one," Fry added. "That tide is going to be inevitable whether there is an historic district or not."