Representatives of the nation's severely depressed housing industry were told this week to expect no help while the Federal Reserve and the Reagan administration work to control inflation.

Stressing that the next 90 to 120 days are "most crucial" in giving the nation a "real chance to decrease inflation by the end of the year," Fed Vice Chairman Frederick Schulz told a residential construction forecast conference here that "there will be pain" for some segments of the economy, including housing and home finance. He added that the Fed will stick with its deflationary progray because there is "no choice."

Schultz and other speakers at the conference, sponsored by the National Association of Home Builders, expressed confidence that long-term mortgage rates would decline when the federal deficit is trimmed and inflation is brought under control. Several economists speaking at the conference predicted that mortgage rates would ease later this year and in 1982, and that housing starts would increase next year and in 1983.

Although long-range predictions were optimistic, a Michigan builder asked how he and others can be expected to survive in overbuilt, undersold areas. He got no answer.

James Burnham of the President's Counsel of Economic Advisers said that the Reagan anti-inflation policy must first "save the economy." He promised no rapid improvement but suggested that monetary restraint and budget cuts will rekindle strong economic growth by 1983.

Economists Lawrence Chimerine predicted that mortgage rates would not drop below 14 percent this year, but said that housing starts would rebound to 1.7 million in 1982 and to 2 million in 1983.

David Jones, another economists, predicted that the rate of inflation would decline to the 7 to 8 percent level by the end of this year and that mortgage rates would drop to the 13 percent range in 1982, triggering an increase in the number of housing starts. He also foresees a decline in the recent rate of housing price appreciation.

Economists Leonard Santow said that the problem of "housing affordability will not go away." He predicted that mortgage rates will remain high and that there would be no special aid for housing, except possibly a tax inducement for savers. But he did predict a drop in the rate of inflation to 9 percent by the end of this year.

At least one Washington-area builder-developer didn't blanch on hearing that homebuilders can expect no special federal favors. Otis Coston Jr., an executive with the Burke Centre partnership in Northern Virginia, suggested that builders will have to "try harder" and maintain a survival pattern until inflation is controlled and money rates decline. He also said that "bail-out programs are not the answer."

Coston and several other area builders pointed out that varied smaller detached houses, town houses and condominiums priced from $60,000 to $100,000 are selling reasonably well, despite high mortgage rates. They also agreed that a latent demand for homeownership has been dammed up recently by conventional mortgage rates over 15 percent and an FHA-VA rate ceiling that recently was raised to a record 14 1/2 percent.