District of Columbia mortgage lenders plan to begin making housing loans as soon as Mayor Marion Barry signs the bill raising the city's usury ceiling to 15 percent.

The D. C. City Council unanimously approved the temporary hike last week and the new law is expected to go into effect within 10 days.

As of last week, according to Peeke & Associates, a mortgage survey firm, fewer than half (47 percent) of 43 banks, savings associations and mortgage bankers were making loans on District property. Some had ceased making funds available as much as a month ago when the deadline for expiration of emergency legislation passed in July began to approach.

The interest rate ceiling stood at 11 percent until mid-summer when it was removed for a 90-day period. The new 15 percent ceiling will also be in force for only 90 days. Legislation creating a permanent 15 percent ceiling for mortgage and consumer loans will have a first reading by the council Oct. 23.

Nine of the 13 institutions that were out of the market altogether reported yesterday they plan to reopen their lending windows. The other four said the current lack of funds will prevent them from doing so. Richard Williams, vice president of Eastern Liberty Federal Savings and Loan, remarked, "We don't like to make loans at these rates. With the cost of (borrowed) money, we must charge 12 1/2 percent plus two points just to break even."

According to the Metropolitan Washington Savings and Loan League, its 21 members reported a net outflow of $16.1 million from savings accounts in August, compared with a $3.3 million loss a year earlier. Depositors are removing their funds and putting them into higher yielding investments. The area's record is considerably worse than for the country as a whole. Federal Home Loan Bank Board statistics show an increase of $729 million in August deposits, versus a $2,069 million rise a year earlier. Although September figures are not yet in, economists predict they will be bad news for Washington.

Of those lenders who were making mortgage funds available only to good customers, and often only with a 25 percent or more down payment, most plan to continue such restricted lending. Only the National Bank of Washington said its loan window is now open to all comers. Moreover it will be charging only 11 percent plus a point each to the buyer and seller.