Interest Reserve

A construction loan does not hand over the full amount at once. The CFPB explains that the money is released "in a series of advances as the construction progresses," and the borrower owes interest only on the portion drawn so far. An interest reserve is the built-in cushion of money that covers those monthly interest charges, so the borrower is not writing an interest check every month on a home they cannot yet live in.

The mechanics are simple. The lender sets aside a calculated amount inside the loan, and each month it draws that period's interest from the reserve rather than billing you directly. As the build progresses and more of the loan is drawn down on the draw schedule, the interest grows, and the reserve absorbs it. This keeps your cash flow clean during construction, which matters if you are also paying rent or a mortgage on your current home.

The reserve is sized up front from estimates: the loan amount, the expected draw pace, the interest rate, and the construction timeline. Because it is an estimate, two things can go wrong. If construction runs long or rates are variable and climb, the reserve can run dry before the home is finished, and you start paying interest out of pocket. Lenders use methods like those in Regulation Z, Appendix D to estimate and disclose interest on these multiple-advance loans.

For example, an Apache Junction borrower with a 12-month build budgets an interest reserve sized to cover roughly a year of interest on a rising balance. If the build slips to 15 months, the reserve may be exhausted, and the last few months of interest come from the borrower's pocket.

When you compare construction loans, ask whether the interest reserve is funded inside the loan, how it was sized, and what happens if the build runs past schedule. A realistic reserve, tied to an honest timeline, keeps a surprise interest bill from hitting at the worst moment.