Rates have inched down about 0.2 percentage points since the Federal Reserve announced plans in September to buy as much as $40 billion a month of mortgage-backed securities until the economic recovery started gaining momentum.
That may be happening already, according to Keith Gumbinger, of mortgage information company HSH.com.
"If the economy continues to show signs of improvement this fall, mortgage rates could firm a little more," he said. "For that to occur though, we'll need a lot more evidence that forward momentum is building."
Frank Nothaft, Freddie Mac's chief economist, said rates remained unchanged this week as "home construction builds up steam."
He noted that construction on single-family homes continues to rise, as does homebuilder confidence, both of which point to an improving housing market.