Despite adjustments for the Labor Day holiday the previous week, mortgage applications surged last week, even amid rising rates.
Total application volume rose 7.9 percent week-to-week, according to the Mortgage Bankers Association (MBA), driven mostly by refinances, which doesn't jibe with the rise in rates.
Applications to refinance rose 10 percent from the previous week, but are still down 22.5 percent on year. Mortgage applications to purchase a home rose 5 percent from the previous week but are down 10 percent on year.
"Given the volatility in activity around the long weekend, it can be helpful to look at the change over a two week span: refinance applications are down 1.4 percent while purchase applications are up 2.1 percent," said Mike Fratantoni, MBA's Chief Economist.
The average contract interest rate for 30-year fixed-rate mortgages with conforming loan balances ($417,000 or less) increased to 4.36 percent, the highest level since June, from 4.27 percent.
"Regardless of the seasonal volatility in the applications numbers, the bigger issues remain. Rates had been stagnant at their lowest levels of the year until moving higher fairly quickly in September, in part based on speculation that today's Federal Reserve announcement would accelerate the rate hike timeline," said Matthew Graham of Mortgage News Daily. "While the Fed's policy rate doesn't directly affect mortgage rates, the indirect effect of such a shift could mean that rates continue moving higher, and that would only be bad for refinance demand."
The refinance share of mortgage activity increased to 57 percent of total applications, the highest level since February, while the adjustable-rate mortgage (ARM) share of activity increased to 7.6 percent.
Read MoreStaging your mansion for $45,000
A snapshot of mortgage volume by Guaranteed Rate, a retail mortgage lender, found that ARMs took off dramatically in the second quarter compared with a year ago, rising from 9 to 16 percent of total loan volume.
"ARMs' rapid rise in the share of the total volume indicates that home buyers are feeling more comfortable with this type of loan product after shying away from it in the wake of the financial crisis," according to the report.