Every time Joyce Rogers decides to move out of her parents' Arlington Home and into an apartment of her own, she runs into an obstacle she can't seem to overcome: her four children.

"They [landlords] always tell me either they don't want any children at all or else I have to many," she says in anguish. "I'm frustrated. I tired of looking."

Rogers' plight is not unusual in the Washington area. With rental housing shrinking under the pressure of condominium conversions and few new units coming on the market, all renters are facing difficulties finding affordable housing in the region.

But for young families with children, the pressures are becoming increasingly acute because more and more apartment owners are hanging "Adults Only" signs on their buildings. "It's aggravating an already existing housing shortage," complains Alfreda Jordan-Webb, director of Alexandria's Landlord-Tenant Office, which estimates that half of the city's 131 apartment complexes have restrictions on children.

Some apartment association officials estimate that one out of seven of the 350,000 apartment units in the area are off-limits to children.

With occupancy rates running at about 96 percent in the area, landlords counter that they can afford to be picky abut their tenants and many claim they are better off without children.

"A lot of people want to be able to live where they don't have the inconvenience or hassle, or noise of children," says Caroline Lewis, a lobbyist for the Metropolitan Washington Apartment and Office Building Association.

What's more, she says all-adult buildings are often more profitable.

"There are no fingerprints in the hallway, no litter, and the buildings are esthetically pleasing. You can't maintain properties at the same standard of elegence when you have children."

That reasoning has alarmed many in the Washington area, who say that landlords are breaking up families with their rules. "In terms of family stability, we think this terrible," argues Sandy Clay, a special assistant at the Childrens Defense Fund, a national organization that promotes the rights of minors.

Doris McMurray, a 34-year-old Washington secretary and mother of seven, says she is forced to chose between qualifying for a four-bedroom apartment in Alexandria or keeping her family intact. "It's either me staying at [my parents'] home where everybody's miserable, or splitting 'em up. I really don't have a choice," she says.

Thus for only one of the region's governments has done anything about the issue. The D.C. City Council, responding to pleas that young families were being forced out of Washington, last month enacted legislation that bans discrimination against families. The law, however, will not become effective until later this year.

Similar legislation died in the Maryland legislature this year and Virginia localities are powerless to act. "There is nothing we really can do about it," notes Jordan-Webb of the Alexandria landlord-tenant office.

Meanwhile, the future is likely to become bleaker for many families because of the lack of new rental properites. "In terms of the housing market here, nobody is building rental units for families with three children or more, except the government," warns D.C. Housing Director Robert L. Moore.

William A. Welch, executive director of the Prince George County Human Relations Commission, says that even though only about 10 percent of the county's apartments are formally registered as "For Adults Only," the situation is much worse. Families with children are forced into the least desirable, most run-down properites, he said. About one of every five complaints his office received in the last year had been from families with children in search of a place to live.

Landlords say that the childless apartments are a response to the housing demands of the swarm of more affluent single and married couples without children in the area.

Joseph Schuble, executive vice president of Dreyfuss Brothers Inc., which has 16,000 apartment units in the area, says it makes economic sense to reduce the number of persons in an apartment.

This is particularly the case if the building owner has to foot the bill for utilities. Few occupants mean less electricity and water.

"A landlord will say to himself, 'Hell, it's not going to hurt me not to rent to people with children, and it'll cost me less,'" Schuble said.

That's an option D.C. landlords soon will lose.

The new law that bans housing discrimination against families with children will require a landlord to allow at least two persons to share an efficiency apartment.

For larger apartments, a formula is established that would permit five people in a two-bedroom apartment or seven in a three-bedroom unit.

Legislation protecting families with children, introduction in the Maryland legislature this year, failed in committee. Prince George's Democratic Del. Thomas J. Mooney, who introduced the measure, says he intends to sponsor a modified version of the bill again next year.