The three-month slide in home mortgage interest rates has ended at a little less than 12 percent and now some rates are bouncing back up a bit, the latest reports on what it costs to borrow money for a house revealed yesterday.

The end of the steady decline showed up clearly in the weekly mortgage auction of the Federal Home Loan Mortgage Corp. where the average rate increased a fraction for the second week in a row. From 11.59 percent on June 25, the Mortgage Corporation's average price climbed to 11.67 percent last week and went up again to 11.89 percent yesterday.

"If someone's thinking of buying a house, it's hardly worth waiting for rates to go lower," said Philip Brinkerhoff, president of FHLMC, which provides mortgage money to lenders.

The effect of the turn-around is expected to be reflected in surveys of the mortgage costs in the Washington area that will be out this weekend.

"I have the feeling that maybe we have bottomed out," Robert Smith, president of Maryland Federal Savings and Loan commented yesterday. "We're at the point where consumers can expect the rate of interest to be about 12 percent for the next couple of months."

Smith and other lenders said the settling of rates in the 11 1/2 to 12 1/2 percent range reflects both the cost of money to saving associations -- which is about the same across the nation -- and the local demand for funds.

Because demand for mortgages in the Washington area has been soft, Maryland Federal cut its rate from 12 percent to 11 1/2 percent yesterday, Smith said. But he said he does not expect the rate to go any lower and predicted it will again creep upward within a few days.

Maryland Federal's 11 1/2 percent rate is the lowest quoted by a Washington lender in months, but Maryland Federal charges a 2 percent loan Origination fee, while many others get only 1 "point" for making a loan.

Savings and loans are now paying about 10 percent interest on 2 1/2-year certificates of deposits -- the most popular form of savings. That means they have to charge more than 11 percent interest on a mortgage, if they are loaning their own funds to a home buyer.

Recently, however, most lenders have been getting their money through the secondary mortgage market by selling their mortgages to the Federal National Mortgage Assn., known as Fannie Mae; the Government National Mortgage Assn., or Ginnie Mae; or the Federal Home loan Mortgage Corp., Freddie Mac.

To sell a mortgage to Freddie Mac, a lender is required to charge at least 3/8 of a percent more than the FHLMC rate and most of them get a slightly wider spread. At yesterday's 11.829 Freddie Mac rate, a lender would have to get at least 12 1/4 percent. Brinkerhoff said he does not believe the increase in FHLMC rates for the second week in a row means mortgage costs are headed back up again, merely that they are bouncing after a dramatic drop.

Three months ago mortgage rates averaged 16 percent and some lenders were charging 17 percent or more.

"I can't say we're actually at the very bottom of the cycle," added Brinkerhoff. "They could possibly go down to 11 percent by the end of the year."

FHLMC, which is chartered by the Federal Home Loan Bank Board, gets money for mortgages by selling what are called "mortgage pass-through securities" on Wall Street. The rates FHLMC must pay for money reflect the interest paid on corporate bonds, which has gone up recently.

Where rates will go in the next few months will depend largely on how bad the recession gets and how soon the economy improves, Brinderhoff added. Bad news for the economy could be good news for borrowers, because interest rates will probably go down.

The recession also discourages families from buying houses. But the lenders expect home buyers to adjust to both the recession and to 12 percent mortgages, and that could increase the demand for funds and push rates back up a little.

The mortgage picture is confused, however, because some rates have not yet completed their slide and are still coming down. Reductions in the FHA and VA rates for mobile home and multi-family-dwelling loans are to go into effect in the next few days. Some private lenders are also expected to trim their rates by a fraction of a point as the market settles down.