WASHINGTON (AP) — Average U.S. rates on fixed mortgages fell this week for a fourth straight week. The low rates could give a boost to the spring home-buying season, which has started slowly.

Mortgage buyer Freddie Mac says the average rate for a 30-year loan declined to 4.14 percent from 4.20 percent last week. The average for the 15-year mortgage eased to 3.25 percent from 3.29 percent.

Warmer weather has yet to boost home-buying as it normally does. Rising prices and higher rates have made affordability a problem for would-be buyers.

U.S home construction surged in April to its highest pace in five months, the government reported last Friday, but nearly all the increase came from the volatile apartment sector — a sign that Americans are still struggling to buy single-family homes.