After a long, bleak summer for the housing industry, the recent modest decline in interest rates has builders and real estate brokers crossing their fingers, hoping for a long-awaited turn of colors from red to black this fall.

So far, 1982 has been the worst year for home sales and home starts since World War II, and recovery whenever it starts is expected to be a long, slow process. The latest rate reductions have not yet resulted in a sales boost, or even an overall increase in traffic, as potential buyers apparently are waiting and assessing the situation, according to real estate brokers and builders.

But economists and industry experts now are making some cautious predilctions about the stirring of a turnaround, provided interest rates take no unexpected jump.

Predictions for where conventional mortgage interest rates will be by the end of the year generally range from about 14 1/2 to 15 1/2 percent, certainly no bargain compared with years past but an improvement from the 17 to 18 percent rates of earlier this year.

The FHA/VA rate now is 14 percent, having been lowered from 15 1/2 percent a month ago, and Housing and Urban Development Secretary Samuel R. Pierce said this week that he expects to see it dropped by another one-half or 1 percentage point in the near future.

If the rates stabilize, 1983 could be a somewhat better year, though still not adding up to a full recovery, and July 1982 could mark the bottom of this housing industry depression, some of the experts are saying.

But most also caution that it will take some time for buyer confidence to be restored and note that unemployment and insecurity over the economy generally will continue to keep many out of the market. In addition, while perhaps providing a psychological boost, the drop in conventional rates has not been so great that it has put home buying within reach for most people.

At an interest rate of 15 percent, for example, it still takes a $50,000 salary to be able to afford an $82,381 mortgage, according to rough estimates cited by real estate sellers. Of course, there are a variety of "creative financing" techniques being used to reduce effective interest rates and monthly payments, mainly sellers holding below-market-rate mortgages, but many of these have met with resistence on the part of consumers.

Adjustable-rate mortgages, which the savings and loan industry wanted to promote widely, in particular have not been accepted by the consumer, who still fears the volatility of interest rates, industry experts report.

Builders have been buying down rates for some time, and the rate to consumers at these projects are likely to stay the same despite the reduction in market rates, local builders say.

Thus far, even traffic of potential buyers has not picked up, according to a poll of members taken this week by the National Association of Realtors, a finding that surprised NAR officials. They speculate that people are taking a "wait-and-see attitude," hoping that rates will go down still further, said NAR spokesman Bill Ellingsworth.

People are even waiting to close on homes they have contracted to buy, hoping the rates will decline farther, he said. Some industry experts say this is natural when rates are on the decline and that if they stabilize or blip up people will take that as a sign they should get into the market now before the rates go back up.

Philip Abrams, Deputy Federal Housing Commissioner, said that a recent poll of FHA area offices found a substantial increase in people calling and asking for FHA forms since the rates were dropped, "the flurry of activity that usually precedes applications for commitments."

"We think it will be a busy September and an even busier October," Abrams said.

The rejuvenation of hope on the part of builders may be the most dramatic turnaround so far resulting from the rate declines. Just last month, the National Association of Home Builders' chief economist, Michael Sumichrast, was saying there would be no upturn this year and that next year could be just as bad.

A monthly survey of builders' sales and projections, which the group has been taking for 25 years, showed that in July builders were about as pessimistic as they had ever been in the past quarter decade on what the next six months would bring. By the end of August, however, there was a major change in that attitude, with close to half of the builders saying they would see "fair" sales in the next six months. In July, 77 percent had said they expected "poor" sales, with less than 20 percent projecting "fair" sales and only a handful looking to "excellent" sales.

This led Sumichrast to predict that sales bottomed out in July and that 1983 will be a "reasonably good" year. He still expects 1982 to edge out 1981 as the worst year for housing starts in the postwar period, however, predicting a total of 1.07 million starts, about half what the industry was producing four years ago.

Even with a turnaround, it would take some time for builders to gear up again, particularly since they have large amounts of unsold inventory to get rid of before they start much rebuildiing. It would take about a year at current sales rates to deplete the country's inventory of 300,000 single-family homes, Census Bureau figures showed.

Even with a gradual increase in sales, however, Sumichrast said home prices would stay down. In real terms, including the value of seller financing, house prices probably have dropped by 10 percent in real terms in the past year, he said. It will take at least two years for prices to really start increasing again, and even then appreciation is unlikely to go back to the double digit rates of the past, he added.

Resales of homes fell to a record low annual rate of 1.86 million in July, less than half the peak rate of 4 million reached in 1978, but National Association of Realtors Chief Economist Jack Carlson also predicted that that would prove to be the bottom of the depression.

Locally, builders and industry specialists have varying reports on traffic of buyers in the past few weeks, but almost all say that the rate declines have not yet resulted in increased sales. Some say it is too early, while others say that August vacations and back-to-school concerns kept people from coming back to the market. And some say the rates simply haven't gotten affordable yet to most buyers.

"Rates haven't gone down far enough to where people would find it attractive to buy," said one real estate expert who asked not to be named. "The rate might as well go from 28 to 26 (percent) as from 18 to 16."

Debbie Rosenstein, a local housing specialist with Housing Data Reports, said that September will be the crucial month for determining whether increased traffic will result in sales.

In the meantime, there have been some bright spots this summer in an otherwise dismal market. Rosenstein said the lower-price town house projects have sold steadily, even before the rate drops.

And Pulte Home Corp.'s line of Victorian-style homes in the Loudoun County community of Country Side has done tremendously well Rosenstein said, saying this is a result of its being as "exciting product" in a moderate price range, though relatively small for single family homes. The project also is between 45 minutes and an hour from downtown, and about onehalf hour from Tysons Corner, according to Pulte.

Pulte Vice President Rodger Kamuf said his company has sold 45 of the Victorian homes so far this year and that 485 couples showed up at a weekend "grand opening" in August, held after sales had begun. The homes are priced from $85,000 to $90,000 with square footage of between 1,200 and 1,500 but he said there is more volume to the homes than that would indicate because the design includes open spaces such as a loft over the living room.

So far, the buyers have tended to be young couples with no children or one child, Kamuf said.

Bob Mitchell, president of C-I Mitchell & Best and president of the Suburban Maryland Home Builders Association, said his company just finished its best three-month period in three years. At the same time, June 1981 to May 1982 were the worst months his firm had experienced, and there is no way they can finish this year without a loss, he added.

Most builders he knows are hanging on, he said, though they would not have been able to do so much longer if they had had to buy rates down from higher levels to what buyers would accept.