The oft-postponed battle over preserving turn-of-the-century buildings north of Dupont Circle on Connecticut Avenue is scheduled to come before the D.C. Zoning Commission Oct. 16.

For almost seven years, civic groups and Dupont Circle residents have urged the commission to rezone three blocks of the avenue, between the circle and Florida Avenue, to prevent the construction of more of the 90-foot office buildings permitted under present zoning.

Last year the commission held hearings and voted to downzone 66 acres in the Dupont Circle neighborhood, dropping maximum building heights from 90 to 60-65 feet in much of the area. But a divided commission declined to rezone Connecticut Avenue itself.

"We're concerned not just about height but density," said Ward Bucher, president of Don't Tear It Down, a local preservation group, and a member of the coalition of Dupont Circle civic groups.

"Most of the buildings here were built between 1880 and 1920, are under 50 feet tall and they all have a resonance with each other, like a piece of avant garde music," Bucher said.

"They are part of an historic district, a registered national landmark, and we don't want to see them replaced with rows of office buildings like that south of the circle . . . which has the same C-3-C zoning."

The 18,000 residents in the Dupont Circle area are overwhelmingly in favor of downzoning, says Advisory Neighborhood Commission chairman William Middleton. "We'd like to preserve what's there and keep the height down, preferably to 50 feet.

Middleton accused the zoning commission of "dragging this on for more than four years now, through two administrations . . . during which time two large buildings have been built" on Connecticut Avenue north of Dupont Circle. One is 90 feet, the other 70-80 feet high.

However, zoning lawyer Norman Glasgow, who represents several businesses with property on the avenue, said this week he feels there are few buildings worthy of preservation along Connecticut and that the new Metro subway station there requires intensive development.

"That station will have one of the largest boarding and reboarding capabilities in the entire Metro system. Why build a great big station if nobody's going to use it?"

Glasgow favors keeping the present zoning because "it also offers the greatest tax benefits . . . for historic preservation, if that's what they (the zoning commissioners) want to accomplish there."

Developers get tax write-offs for the amount of space they give up by preserving as building and not developing a lot to its maximum zoning potential.

Whether the commission keeps the existing zone or rezones, its actions will be reviewed by both the National Capitol Planning Commission and the Joint Committee on Landmarks. The federal agencies were established to protect the historic character of the nation's capital, and both were influential last year in urging the City Zoning Commission to downzone most of the Dupont Circle area. They are expected to favor some downzoning along what civic groups call "the heart of the Dupont Circle historic district."

Six zones to be considered at the commission hearing Oct. 16 at 1:30 p.m. in Room 11A of the District Building will range from the existing C-3-C zone, which permits the highest buildings and most massive buildings, down to C-2-A, the zone favored by civic groups.

The C-3-C zone allows 90-foot buildings with a floor area ratio (FAR) of 6.5, while the C-2-A zone permits only 50-foot buildings with a maximum FAR of 2.5 for residential use and 1.5 for office buildings.

FAR is the relationship between a lot's size and the size of a building permitted on it. A 20,000 square foot lot with a FAR of 3 means a 30,000 square foot building can be constructed.