The refinance share of conventional activity decreased to 83.8 percent from 84.1 the previous week while the refinance share of government activity increased from 48.6 percent to 49.4 percent this week.
Meanwhile, the refinance share of mortgage activity decreased to 77.1 percent of total applications from 77.3 percent the previous week, the fourth straight week of decline.
The adjustable-rate mortgage share of activity decreased to 5.8 percent from 5.9 percent of total applications from the previous week.
The Pacific region led the way in mortgage application activity, increasing by 7.5 percent in September, while the the Mid-Atlantic region had the largest drop, falling 1.9 percent.
Refinancing increased the most in the East North Central region, rising by 8.6 percent, while the Pacific region increased the least, rising by 0.5 percent.
Vermont had the largest increase in refinance applications in September but also the largest decrease in purchase applications. Conversely, Wyoming had the largest increase in purchase applications but the largest decrease in refinance applications.
The average contract interest rate for 30-year fixed-rate mortgages with conforming loan balances ($417,500 or less) decreased to 4.31 percent from 4.33.
Average 30-year fixed-rate mortgages with jumbo loan balances (greater than $417,500) increased to 4.69 percent from 4.68.
For 30-year fixed-rate mortgages backed by the Federal Housing Administration, rates decreased to 4.09 percent from 4.11 percent.
The average contract interest rate for 15-year fixed-rate mortgages increased to 3.63 percent from 3.62 percent.