The District Zoning Commission today may approve construction of a 10-story office building on Washington's Judiciary Square, three stories higher than existing buildings around the square and in apparent disregard of the city's own 90-foot height limit for buildings in the area.

The National Capital Planning Commission last week opposed any increase in the height or massiveness of buildings around the historic square, as did the Joint Committee on Landmarks last month. The Planning Commission has urged the Zoning Commission to delay its decision for at least 60 days.

At least two other lots around the square also will be affected by the decision City officials have said they will apply for zoning to allow 120-foot buildings on those plats if they win it on this one. One is the proposed site of a new municipal office building, where present city officials are considering putting the mayor's office and a new City Council chamber. The other is now vacant.

Washington has had a maximum 130-foot building height limit since 1910, primarily to prevent "skyscrapers" from dwarfing historic federal buildings. However, both the zoning and planning commissions this year approved a 160-foot or 16-story height limit along the north side of Pennsylvania Avenue between 10th and 15th streets NW.

The Zoning Commission, which can ignore the opinions of both the Planning Commission and the Landmarks Committee, gave preliminary approval Oct. 30 to the zoning change that would permit the 10-story building on Judiciary Square, plus an 18-foot utilities "penthouse" on top.

The site, bounded by 4th, 5th, D and E streets NW, just north of Pennsylvannia Avenue, is on the west side of Judiciary Square. It is owned by Georgetown University, which maintained its law school there from 1898 until 1973, when the old building was demolished. The law school moved into a new building a block away, at 600 New Jersey Ave. The site is now a parking lot.

City and university officials, and an attorney for the developer, who was not identified, all told the Planning Commission last week that it would not be economical to build a 90-foot building of the size allowed under present zoning.

The present master plan not only limits building heights around the historic square to 90 feet, but requires a 40-foot setback from 5th Street along the square and a maximum floor area ratio of 6. The Zoning Commission proposes to approve a floor area ratio of 7, which means a more massive building could be built on the site.

Judiciary Sauare, one of the original squares in the 1791 L'Enfant plan for the federal city, is itself a federal historic landmark, as are two buildings at its north and south ends:

The old City Hall, built about 1820 and considered one of the finest Greek Revival buildings in the Nation's Capital;

And the 1885 Pension Building, built to honor and provide pensions for Union Civil War veterans and considered to have Washington's most magnificent interior space.

A proposal to renovate the Pension Building and turn it into a national museum of the building arts, "The Building Building," was given tentative approval by Congress in October and is now being studied by federal agencies.

The 158-foot Pension Buildings is the tallest building around the square. The old City Hall and District courthouse buildings inside the square range from 40-50 feet. And buildings recently constructed around the square-Metro headquarters, the new Labor Department building and the new city courthouse-all are 90 feet, in accordance with the city's 1971 master plan for the area.

The staff of the Planning Commission, the federal planning agency for the Washington area, has said a 120-foot building not only would violate the master plan and the city's own downtown urban renewal plan-which also has a 90-foot height limit-but would be inconsistent with the "planned unit development" (PUD) zone the city is proposing for the law school site.

A PUD zone allows for greater flexibility in design, including building height increases, but such changes are prohibited if "they do not enhance the neighborhood," according to its regulations.

Ben Gilbert, director of the city's Municipal Planning Office and Mayor Walter Washington's alternate on the Planning Commission, acknowledged that a 120-foot building would violate the master plan and urban renewal plan.

But last week he dismissed the 1971 master plan as "hopelessly out of date. . . and obsolete" and called the city's urban renewal plan "not binding" upon the city, "just a general guide of where we want to go."

No one spoke against raising the height limit at Zoning Commission hearings last spring, according to Steven Sher, executive director of the commission. Only one citizen spoke at the Planning Commission meeting last week. Harriet B. Hubbard, a member of the Dupont Circle Citizens Association, called the proposed building a "hideous" desecration of a "beautiful square" for which no one is speaking up because "no one lives down there."