WASHINGTON » Average U.S. mortgage rates rose this week but remained near historic lows. Cheaper mortgages have encouraged more home buying and refinancing.

Mortgage buyer Freddie Mac said today that the average rate for the 30-year fixed mortgage edged up to 3.42 percent from 3.35 percent last week. That’s still near the average of 3.31 percent reached in November, the lowest on records dating to 1971.

The average on the 15-year fixed-rate loan rose to 2.61 percent from 2.56 percent last week, which was the lowest on records going back to 1991.

Low mortgage rates have buttressed the housing recovery that began last year. Home sales and construction are up from a year ago, and prices are rising in most U.S. markets.

A survey released Tuesday showed that U.S. home prices rose 10.5 percent in March compared with a year earlier, the biggest year-over-year gain since March 2006.

The survey from Core Logic, a real estate data provider, showed that year-over-year prices have risen for 13 straight months. Prices are rising in part because more buyers are bidding on a limited supply of homes for sale.

Prices rose in 46 states over the past year. Eleven states posted double-digit gains.

And excluding distressed sales, which comprise foreclosures and short sales, prices rose in every state. A short sale is when a home sells for less than what’s owed on the mortgage.

Sales are rising in some markets hit hardest by the housing bust in part because investors are scooping up homes in hopes of turning a profit.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country on Monday through Wednesday 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 mortgages was 0.7 point, unchanged from last week. The fee for 15-year loans also held steady at 0.7 point.

The average rate on a one-year adjustable-rate mortgage fell to 2.53 percent from 2.56 percent last week. The fee for one-year adjustable-rate loans rose to 0.4 point from 0.3 point.

The average rate on a five-year adjustable-rate mortgage increased to 2.58 percent from 2.56 percent. The fee was unchanged at 0.5 point.