Construction-to-Perm Loan Rate Lock Calculator
Construction-to-perm loans roll your construction loan into a 30-year mortgage at closing — one set of fees, one rate lock. Extended locks (12-18 months) protect against rate rises while you build.
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A construction-to-permanent (single-close) loan combines your construction financing and your 30-year mortgage into one loan with one closing. The construction phase pays interest-only on draws; once construction completes, the loan converts to permanent amortization at the rate locked at the original closing. This protects you from rising rates during the build period.
Single-Close vs Two-Close Construction Loans
Single-close (construction-to-perm): One application, one set of closing costs (~$5,000 saved), one appraisal, rate locked upfront. Best when rates may rise during construction. Two-close: Separate construction loan (short-term, interest-only) then refinance into a permanent mortgage at completion. Best when rates may fall — you re-shop rates at conversion. Single-close requires the lender to underwrite as if construction is already complete, so qualifying ratios use the projected as-built value and final perm payment.
Extended Rate-Lock Options
Standard rate locks last 30-60 days — useless for a 12-month build. Extended locks: 6-month locks are typically free, 9-month locks cost about 0.25% of the loan, 12-month locks cost 0.5%, 18-month locks cost 1% or more. Many lenders offer a one-time float-down option (lower your locked rate once if market rates drop 0.25%+ during the lock period) for an additional 0.125-0.25% fee. The decision: if you expect rates to rise during your build, the lock fee is cheap insurance. If you expect rates to fall, consider a two-close structure or a shorter lock with float-down.
Last updated May 2026. Sources: CFPB Mortgage Guide.