For Madeline Vines, a Silver Spring receptionist with two teen-aged children, the rent bill looms large each month, a monstrous necessity consuming about two dollars out of every five that she and her husband earn.

"We're constantly robbing Peter to pay Paul," Vines said. "We really can't afford to vacation or to see a nice play. But occasionally we do it anyway, and then it throws us behind. We just can't make ends meet. It's causing family problems, family pressures. I don't know what to do. I need help so we can breathe."

The Vineses are among an estimated 110,000 families in the Washington metropolitan area who pay more than 35 percent of their income for housing -- a steep increase from the traditional pattern in which housing costs normally consumed one-quarter of a household's income.

Their growing ranks make up more than one out of every five tenant households in the area. They include working people, young singles, the elderly, the unemployed, and those on fixed incomes. Some are poor and pay disproportionate amounts of their incomes for housing simply because they have no choice. Government-subsidized housing, which could lower their housing costs based on income, is limited.

Others who have more money willingly pay the high costs to live in a neighborhood they like.

The trend toward higher housing costs includes not only tenants but homeowners as well.

In a national study of home buyers, the U.S. League of Savings Associations found that more than 45 percent of the people who bought homes last year paid more than 25 percent of their household income for housing expenses, which included the mortgage payment, real estate taxes, utilities, and hazard insurance. In 1977, only 38.1 percent were in that situation.

Locally, the numbers were even more dramatic. Last year, more than half -- 51.2 percent -- of the area's home buyers who bought their homes through savings and loans associations paid more than a quarter of their household income for housing. In 1977, only about 36 percent had done so.

As housing costs have risen, so has the willingness of the homebuying population to pay larger portions of their income for housing. For many of these people, the traditional American dream of owning their own home has outweighed all other considerations. Their optimism remains strong that their salaries will rise steadily and eventually ease the burden of high monthly mortgage payment.

For years, the rule of thumb was that housing costs shouldn't exceed one-fourth of household income. Although it was a rule that often was broken depending on individual situations, it governed many decisions by both homeowners and lending institutions about how high a price people could pay for housing. But in recent years, that tradition has been abandoned by more and more people as rental housing has become scarce and homeownership has become more costly.

One Springfield couple pays about 35 percent of their gross income -- and nearly half their take-home pay -- to rent a house for $400 a month.

The expense means the couple, who have four children, are on a "very strict budget," said the wife, who asked not to be identified.

"You don't go to the doctor every time you have an ache or a pain. You go only when the ache is so bad you can't stand it," she said. "We do without quite a bit. I guess I must know about 8,000 ways to cook a potato."

The family gets about $90 a month in food stamps. Their entertainment is an occasional cookout in the backyard. The last movie they saw was "Star Wars" two years ago. They have little money to pay for gasoline, and the wife said she goes to the hairdresser maybe once a year.

Some months, utility costs add as much as several hundred dollars to the couple's already steep housing costs.

So why do they sacrifice, instead of renting a cheaper apartment or house? Because when she lived in a ramshackle apartment complex in Alexandria years ago, she dreamed of having her own rambler in Springfield, the woman said. Even though her house is rented, she considers it her own and doesn't want to give up its advantages.

"It's our first house, and the first yard for our children," she said. "I'm not about to go backward now."

Some tenants who are better off find Washington apartments a bargain, a rent-controlled bonus that enables them to pay low portions of their income for housing. For others, the situation is often bleak.

In one Northwest Washington apartment building where the Metropolitan Washington Planning and Housing Association is helping tenants buy the project and convert it to cooperatives, half of the 26 tenants who filled out forms said they pay more than 30 percent of their income for rent. In a Southeast Washington building, about 40 percent of the 96 tenants said they pay more than 30 percent, according to Larry Weston, director of cooperative housing services for the organization.

"The numbers tell me how serious it is out there," Weston said. "Sometimes I get the feeling that half the people in the city are paying more than 30 percent of their income for housing."

A payroll clerk who lives in Silver Spring estimated that 46 percent of her gross income goes for rent. She asked that her name not be published because she fears eviction if her landlord discovers that she doesn't earn her monthly rent in one week's salary -- the standard that many landlords use to determine of a tenant is qualified.

"We're broke most of the time," the woman said. "Every dime has to count. The rent comes first. Then we sit down and decide on the rest." Her three children got no new school clothes this year.

The rent on Cathy Osborne's two-bedroom Falls Church apartment was $240 a month when she moved in last August. It now is $300 -- only $45 less than her monthly income.

"I'm roughing it," Osborne said. "I'm looking for a babysitting job now. I haven't gotten anywhere this summer." Osborne said she gets $112 a month in food stamps, and bought her children school clothes from her savings. She is separated from her husband.

Osborne is optimistic about her future, nevertheless. The Fairfax County housing authority is trying to buy the Falls Church apartment complex where she lives. If it does, Osborne said she has been told the rent she pays may be decreased to about $89 a month with the assistance of government subsidies.

Until the mid-1970s, there was no reason for homeowners to stretch their income much more than the traditional one-quarter rule for housing, according to Thomas J. Parliment, an economist with the U.S. League of Savings Associations.

"But by 1979, 25 percent was no longer the rule," she said. "It was overruled by the marketplace."

Parliment noted that the character of the home buying market has changed. More people can afford higher housing costs now because they have little debt and few family expenses -- more singles, young married couples without children, two-income couples, unmarried couples.

"There are really good reasons why people stretch," Parliment said. "There are the investment aspects of buying. It's a hedge against inflation, it's a tax subsidy, and there are capital gains. Those represent pretty heavy reasons.

"We have been asked if it's wise to allow people to stretch their budgets. You have to look at allowing a person to make a short-run sacrifice in their long-run interests."

James Caron, 32, stretched to buy his Capitol Hill row house last year. Caron went from sharing a house whose rent cost him about 10 to 15 percent of his monthly income to owning a home with a mortgage payment and property taxes eating up more than 35 percent of his salary -- and that doesn't include utilities.

Last year, he took a vacation to South America. This year, he couldn't afford to go anywhere.

"It's tough," said Caron, an economist. "I'm buying furniture very slowly. Many of the things I did before, I don't do now. My house is liveable, but it needs extensive renovation -- maybe $30,000 worth of work. But I'm willing to make the sacrifice."

Caron expects a salary increase later this month, which should drop his housing cost to about 30 percent of his income.

James Harris, president of Washington Federal Savings and Loan Association and of the Metropolitan Washington Savings and Loan League, said that many people buy homes with big mortgages because they expect salary increases.

"I always thought the 25 percent ratio was a little low, personally," Harris said. "It depends on the individual situation."

W. Bradley Griggs, senior vice president of National Permanent Federal Savings and Loan, noted that as interest rates climb -- and they're now at about 13 1/2 percent in the Washington area -- monthly payments in turn increase.

"More and more people are spending more than 25 percent for housing," Griggs said. "It's more like 30 percent now."

One reason for increasing lender flexibility is that the two congressionally-chartered companies which buy mortgage loans from lenders have relaxed their loan underwriting standards in recent years.

Lenders have been notified tha the old policy of a home buyer spending no more than 25 percent of monthly income to get a mortgage is only a benchmark, not a regulation cast in concrete.

Officials of the Federal Home Loan Mortgage Corp. said in a press release last year that the ratio is better stated "as a 25 to 28 percent range, and properly applied only as a general guideline."