A tight middle-class housing market and rising college enrollments in the District are teaching parents and students new lessons about the concept of room and board.

At Catholic University, 100 students this fall moved into a mini trailer park because of a record freshman class while the school builds a new dorm.

At American University, about 180 students will spend the semester, rather than a transitional week or so, in double dorm rooms turned into triples.

George Washington University this summer spent $19 million for a former hotel to help house a record number of freshmen. An 18th dorm, meanwhile, will open in two years.

And Georgetown University students have discovered that some vintage Georgetown row houses long rented out as group houses have been sold off to families, as longtime landlords take advantage of the attractive real estate market.

Real estate agents also report that the number of condominium and co-op sales to parents and students near George Washington and Georgetown are up, though the percentage of college-associated sales still is small when compared with total sales.

Resheda and Ralph Hagen of Oak Ridge, Tenn., for example, never expected to buy a $200,000 Foggy Bottom condo for their daughter to live in while she attends George Washington University.

The Hagens don't think of themselves as wealthy. But the small-business owners bought a two-bedroom unit for daughter Rachel in May after "a frantic, surreal search" for rental housing within walking distance of the campus. And Resheda Hagen said the family thought they were "outrageously lucky" even to have found a close-in condo.

Howard University, one of the nation's most prestigious black colleges, seems to be ducking this particular demographic bullet. A Howard official said only 3,274 of the 3,735 dorm rooms are filled.

Nonetheless, the situation at the other schools here--tight quarters on campus and tight quarters near campus--is not unusual. Colleges around the nation are dealing with housing issues as the "baby boom echo" reaches the campus. Nationally, more young people--14.9 million--are in college than ever, and more prospective students are applying to college than ever. The number is not supposed to peak until 2008, according to Education Department projections.

Boston, with more than 32 colleges and universities within the city limits and a vacancy rate for rental property of less than 2 percent, is experiencing some of the tightest problems. The District's vacancy rate for big, expensive rental buildings is considered to be near its historic low, at 0.3 percent in one survey, although the Census Bureau said the city overall has a 12.6 percent vacancy rate.

Large suburban campuses around Washington, like the University of Maryland, also are experiencing a housing crunch and building new dorms. But off-campus housing in those areas is considered more varied than the options near the more expensive schools in the District.

Finding housing around George Washington University, the city's largest school, has always been tricky. Students are not required to live on campus, and the large number of graduate and medical students often scoop up the better apartments. But this year's enrollment of 19,000, with its record freshman class--2,200, compared with 1,873 a year ago--is further testing students' ingenuity, and the university's.

To keep up with on-campus demand, George Washington this summer converted the former Howard Johnson's hotel across the street from the Watergate apartment building into housing for 366 freshmen. Another 400-bed dorm should open in two years.

The housing crunch around George Washington is mirrored on a much smaller scale around Georgetown University, its more exclusive sibling. The neighborhoods near Georgetown contain very few apartment buildings, so students depend on group houses, room rentals in private houses and apartment and condo rentals across the river. To students and agents, rentals near the school seem tighter than usual, and some long-standing group houses have disappeared in the recent selling frenzy.

So, although Georgetown has held enrollment steady at about 5,500 undergraduates, the options off campus seem to be even fewer than normal.

Georgetown University spokesman Daniel Wackerman said the school is responding to reports of a growing pinch and to perennial complaints from neighborhood associations about group houses by building a 780-bed dorm complex near McDonough Gym. The $120 million project--three residence halls, a dining facility, a new residence for the Jesuit community and underground parking--is to open in 2002.

The school already houses a bigger percentage of students than any school in the District except Gallaudet University for the deaf. With the new beds, on-campus capacity will jump from 78 percent to 92 percent of undergrads.

There always has been a small percentage of parents who bought near George Washington and Georgetown, in Foggy Bottom's pool of efficiencies and small bedrooms and in Rosslyn's larger apartment complexes. Thomas P. Murphy, a Pardoe Real Estate Inc. agent who claims the most District condo sales, said: "If you're going to have a child here for three years or four years, it is foolish not to buy."

And sales seem to be up a bit. Murphy said his total condo and co-op sales have steadily increased to "the hottest market" since he started in 1982. "And there will be a larger increase next year, because rents are on a trampoline now," he said, referring to an effect of the tight housing market.

Murphy credits higher sales to the $5,000 tax credit for first-time home buyers in the District. He said it is $125 a month cheaper to buy a Foggy Bottom efficiency than rent one, and $175 a month cheaper to buy a one-bedroom. Efficiencies run from $45,000 to $60,000, and one-bedrooms from $58,000 to $90,000 near George Washington, he said.

The option definitely sold Sarah Reece, 21, a George Washington senior and pre-med student from Salem, Ore. She bought a two-bedroom co-op at 24th and H streets NW this summer, using money from her grandmother for the 25 percent down payment.

The $82,000 investment, including a $365 monthly co-op fee, will cost only $792 a month, Reece said. Housing at George Washington ranges from $5,500 to $7,000 for 10 months, or $550 to $700 a month.

"I just basically did it because it was a smart thing to do," she said. "The market was going up when we bought it, and we should be able to get back what we've invested if we sell it in five years."

Teresa Chen of Queens, N.Y., knows from crowded neighborhoods. But the 18-year-old was unprepared for freshman life this fall in a double dorm room turned into a triple at American University. Chen describes the corner room as "extremely tight" for the $1,697 it costs each student per semester. But the three roommates recently passed up the opportunity to "de-triple" rather than choose who would have to leave.

Lauren Davern, who shares with Erin Koch of Richmond and another American University freshman, said she has heard "about fights" caused by the tight quarters. But her roommates have not only learned to get along but to relish the $1,000 a semester each is saving by not being in a double. "Any problems we have, we talk about it," Davern said.

About 180 American University students are living in makeshift triples this semester because upperclassmen either couldn't or didn't move off campus. Though enrollment has stayed steady at 11,000 students, with 4,700 full-time undergraduates, the need to keep temporary triples indicates how tight the market is, said Julie Weber, director of residential life and housing services.

Another sign is the big jump in the number of people who consulted the school's housing site on the Internet. The site got about 114,000 "hits" from January to September, 60 percent more than a year ago.

Catholic University's answer to the housing pinch was trailers or, as the school prefers to call them, "modular units." Freshmen at Catholic are required to live on campus, but there was a record number of them--802--this fall. To make room, about 100 upperclassmen volunteered for life in "Curley Court."

Catholic paid $1.4 million to buy, ship and set up the units. The school reports few complaints since the initial settling-in phase, when air conditioners and toilets didn't work properly.

Far from complaining, junior Matt Quinn of Ridgewood, N.J., "loves" his comfortably trashed mobile home because of the spacious living room.

Meanwhile, Catholic spokeswoman Rosemary Harty speculates that tighter rental housing in Brookland is pushing students to other stops on the Metro line, like Silver Spring, that have a bigger array of apartments.

Catholic plans to open a 345-bed dorm for upperclassmen by fall 2001.

Not to be overlooked in any discussion of off-campus student housing are nearby homeowners who worry about property values, congestion, parking and noise. George Washington, for instance, has incensed Foggy Bottom activists with its Howard Johnson's purchase.

Local Advisory Neighborhood Commissioner Maria Tyler and others see the decision to buy outside the established campus boundaries and the rising enrollment as more threats to the neighborhood and the city tax base.

Other activists, meanwhile, are worried about expansion of the George Washington campus at the old Mount Vernon women's college at Foxhall Road and W Street NW. The university is planning to renovate several buildings on the 120-year-old campus and add dorm rooms. All 240 beds at the campus now are filled.

Georgetown also has encountered objections to plans to increase undergraduate enrollment by 500 over the next 10 years. Area homeowners have said the increase would negate the value of the 780 new beds.

For one Georgetown student and his family, though, the housing situation looks incredibly rosy. New Jersey trial lawyer James Supple and his wife bought a two-bedroom row house, with a finished basement, on P Street NW in January for more than $400,000. Although Supple, a Georgetown alum, bought because he and his family spend a lot of weekends and summers here, it also worked out that son Adam, 21, a junior at Georgetown, could move into the house this semester with three roommates. Next year, a second sibling in a dorm at Georgetown may move in.

And, there are two more Supples, one in high school and one in the sixth grade, who may find the house useful someday. And eventually, James Supple said, he may even retire there.

GWU Finds a Fund-Raiser in Its Housing Lottery

How much is a room on the George Washington University campus worth? This year's charity auction of the Top 10 room picks in the school's housing lottery offers a clue.

The first room auctioned off went to two students for $4,500. They chose a rare apartment for two people, rather than four, in a new building on campus. Their winning bid was above and beyond the $7,030 it will cost them to live there for 10 months. George Washington dorm space ranges in price from $5,500 to $7,030 per school year per student.

George Washington raffled off the first pick of all rooms, at $1 a chance. The Residence Hall Association got about $600 from raffle ticket buyers.

In all, the Resident Hall Association's "Martha's Marathon" (named for, you know, George W.'s wife) raised $35,000 for housing assistance from rooms and other donated items, including lunch with a congressman.

Meanwhile, Georgetown University's senior class at one time auctioned off a room as a fund-raiser, but no longer does.