WASHINGTON » The average U.S. rate on the 30-year fixed mortgage was unchanged for a second week, remaining near historic lows. The average rate on the 15-year mortgage also stayed the same. Low mortgage rates are helping to strengthen the housing recovery.

Mortgage buyer Freddie Mac said Thursday that the rate on the 30-year low stayed at 3.53 percent. That’s near the 3.31 percent reached in November, which was the lowest on record going back to 1971.

The rate on the 15-year fixed mortgage stayed at 2.77 percent for a second week. The record low is 2.63 percent.

The one-year adjustable mortgage was the only rate to change this week. It averaged 2.61 percent, up from 2.53 percent last week.

Cheap mortgages are giving a boost to the slowly improving housing market.

Increased sales have helped to push home prices up, which makes consumers feel wealthier and helps to boost consumer spending. In addition, the increased housing demand is boosting new home construction.

Still, housing has a long way to go to achieve a full recovery. And many people are unable to take advantage of the low rates, either because they can’t qualify under stricter lending rules or they lack the money to meet larger down payment requirements.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country on Monday through Wednesday of each week. The average doesn’t include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for 30-year loans was 0.8 point, the same as last week. The fee for 15-year mortgages was 0.8 point, up from 0.7 point last week. The fee for one-year adjustable rate mortgages was 0.3 point, down from 0.4 point last week.

Freddie Mac said that the average rate on five-year adjustable-rate mortgages edged up to 2.64 percent this week from 2.63 percent last week. The fee stayed the same at 0.6 point.