For five years, John J. Bell has lived in the red-brick apartment complex on Alexandria's north side, watching while the occupants became more heavily low-income and the buildings more and more frayed.

Elsewhere in the city, meanwhile, real estate prices were soaring and developers scrambled for the increasingly scarce open land.

Now the land where Bell's apartment is located, on Bashford Lane near the George Washington Parkway, has become far more valuable than the buildings themselves, and that means something to Bell and his neighbors.

It means they are going to be forced to move.

Last night the Alexandria City Council was expected to give final approval to a development firm, Baker and Sanders, to tear down the 169 Bashford Lane apartments, where a one-bedroom rents for $200 a month. In their place will go 144 town houses, to be priced at more than $100,000 each.

The anticipated action is part of a major trend in Alexandria in which low and moderately priced rental units are being replaced in high-priced new town houses and condominimums.

Bell and many of his fellow occupants seem more resigned to the inevitable than angry.

"In 10 years Alexandria is going to be just for the upper class, with no people of moderate income here at all," said Bell, a civilian employe at the Pentagon. "There are very few places for people who can pay moderate rents to live in Alexandria."

Soon there will be even fewer. Within walking distance of the proposed Baker and Sanders development, another 120 apartments already are slated for demolition and 156 others may be converted to expansive condominiums.

Harold D. Baker, a partner in Baker and Sanders, said his firm's project, tentatively known as Virginia Villages, will start next spring if all goes smoothly.

"We probably will tear down the (two) buildings along Bashford Lane first, and then build our first homes there. The project is expected to take three or four years." The first town houses will be ready for occupancy in late summer, the developers said.

Current residents on the five-acre site - bounded by Bashford, Porter Road, Abingdon Drive and Second Street - will be assisted in finding new homes by the developer.

City officials cite the attractions of the Bashford Lane area and broader shifts in city statistics for the changing nature of the area, which was a segregated enclave for federal employes nearly 40 years ago.

"That area in the northern part of the city is picking up spillover from Old Town, where prices are similar to Georgetown's," said Engin Artemel, director of the city's department of planning and community development.

"It's close to Washington and Old Town, and within walking distance of the Braddock Road Metro station." The station is scheduled to open in 1981.

Citywide, the proportion of owner-occupied homes fell from 37 percent in 1960 to 24 percent by 1974, according to Artemel - a cause for alarm among planners because homeowners pay property taxes and renters do not.

"This year, the figure has climbed to nearly 29 percent and we think it will continue to climb," Artemel said.

But the good economic news for the city did not win praise from some of those scheduled to be displaced.

"Where do low-income people go?" said Clinton Hollins, a resident of the Bashford Lane complex. "There's just no place in Northern Virginia for people of moderate means."