Mortgage rates hit new record lows last week, spurring growth in loan application filings.

The Mortgage Bankers Association says applications increased 2.8% for the week ending Sept. 21. The trade group attributes this uptick to a 3% jump in the refinancing index and 1% growth in the purchase index.

Refinance applications represented 81.2% of all filings during the survey period, the highest share since early August.  

Low mortgage rates encouraged the increase in applications with the 30-year, fixed-rate mortgage with a conforming loan limit falling to 3.63% from 3.72%.

In addition, the average contract rate for the 30-year, jumbo declined to 3.87% from 3.99% a week earlier, making it the lowest survey rate to date.

The 30-year, FHA-backed loan saw its interest rate also plummet from 3.50% to a new record low of 3.44%.  

The 15-year, FRM also set a historical record, falling to 2.98% from 3.03% a week earlier.

Meanwhile, the 5/1 ARM remained unchanged at 2.61%.