When you get a standard purchase mortgage, rate lock management is simple: lock your rate for 30 or 45 days, close before it expires, done. The primary risk is a few thousand dollars if rates move before you close and you need to extend the lock.
A physician construction loan operates on a fundamentally different timeline. If your build takes 10 to 14 months — which is typical for a custom home — you're exposed to rate movement for the entire construction period, a year or more before you convert to permanent financing. In a market where rates have moved 100–150 basis points in either direction in a 12-month window, that exposure is meaningful.
This is the rate lock problem on construction loans. It's solvable, but the solution you choose involves a real cost tradeoff.
Understanding the Two-Phase Structure
Construction loans have two phases, and rate exposure applies differently to each.
Phase 1: The construction period. The loan is interest-only. You're drawing funds as the build progresses and paying interest on the outstanding balance (often from an interest reserve built into the loan). The rate during this phase is typically a variable rate — often prime plus a margin. Rate movements affect your monthly interest cost during construction, but this phase ends when construction is complete.
Phase 2: The permanent loan. When construction is complete, the loan "converts" (in a one-time-close program) or you take out a new mortgage (in a two-close program). This is the rate that determines your payment for the next 30 years. It's the one that matters most.
The rate lock problem is primarily about Phase 2 — what rate will you get when the build is done?
One-Time-Close (OTC) Programs: Lock Now, Build Later
The most common solution physician borrowers encounter is the one-time-close (OTC) construction-to-permanent loan, sometimes called a "C2P" or "construction perm." In this structure, you close once — before construction begins — and the loan automatically converts to permanent financing when the certificate of occupancy is issued.
Critically, some OTC programs allow you to lock your permanent interest rate at initial closing, before the build starts. This means that if rates rise 75 basis points while your house is being built, you pay the rate you locked — not the market rate at conversion.
The cost of this protection: Extended rate locks are not free. A 12-month rate lock on an OTC construction loan typically carries a premium of 0.25%–0.75% in rate above what a standard 30–45 day lock would price at, or an equivalent upfront fee (sometimes called lock extension fees). On a $750,000 loan, a 0.50% rate premium costs roughly $22,500 in additional interest over the first three years alone.
That premium isn't necessarily bad — it's the price of certainty. But it needs to be compared against the alternative, which is accepting rate risk.
The float-down option: Some OTC programs offer a float-down, which allows you to reset to a lower rate if market rates decline by a defined amount (typically 0.50% or more) before your build is complete. Float-downs usually cost extra, but they give you downside protection without completely giving up upside. Ask your lender explicitly whether a float-down is available on their OTC program.
Two-Close Programs: Cheaper During the Build, Exposed at Conversion
The alternative structure is a two-close construction loan. You take out a separate construction loan for the build period (often at a variable rate), and then at the end of construction, you pay it off by closing on a new permanent mortgage — a standard refinance-style transaction.
The advantage: you can shop and lock your permanent rate closer to conversion, when you have much better visibility on the timeline and the actual completion date. You're only locking for 30–60 days, which is cheap.
The disadvantage: you have no protection against rate movement during the build. If rates rise 100 basis points while your house is being framed, you'll pay market rates when you convert. You also pay two full sets of closing costs.
For physicians who have flexibility on timing — those who could delay conversion by a few months if rates were temporarily elevated, or who plan to refinance anyway — two-close programs can be the right choice. For physicians who need the certainty and are buying in a period of rate volatility, OTC with an extended lock is often worth the premium.
Float-Down Details: Reading the Fine Print
If you're using a long rate lock and your lender offers a float-down, understand exactly how it works before you count on it:
Trigger threshold. Float-downs typically require rates to have fallen by a minimum amount (often 0.50%) from your locked rate before they activate. A 0.40% drop doesn't trigger anything.
How far it resets. Some float-downs reset you to current market minus a small spread. Others reset you only halfway to the new market. The difference is significant.
Timing window. Float-downs usually must be exercised within a specific window before your expected conversion date — often 30 to 60 days out. If you're still in month 8 of a 14-month build, you may not be in the window yet even if rates have dropped significantly.
One-time exercise. Most float-downs can only be used once. If you use it and rates drop further, you won't get another reset.
Get all of this in writing before you lock.
What Rate Movement Looks Like in Practice
To make this concrete: in 2022 and 2023, 30-year mortgage rates moved from roughly 3.5% to over 7.0% in under 18 months. A physician who started a construction project in early 2022 and converted to permanent financing in early 2023 — without a rate lock — would have seen their payment on a $750,000 loan increase by roughly $2,000 per month.
That's an extreme scenario, but rates moved 50–75 basis points in each direction multiple times during 2024 and 2025. Even modest movements affect payments meaningfully at physician loan sizes.
The Comparison to Make Before You Choose
Before selecting an OTC with extended lock vs. a two-close program, run this comparison:
- What is the OTC program's all-in rate (including the lock premium) vs. what would a two-close permanent mortgage likely cost at projected completion? Get real quotes for both.
- How volatile is the current rate environment? If the 10-year Treasury yield has been range-bound for six months, the cost of locking is harder to justify. If there's significant macro uncertainty, the premium for certainty has more value.
- How firm is your timeline? OTC programs are most efficient when the build comes in on schedule. If your project runs 3 months long and pushes past the lock expiration, you'll pay extension fees — sometimes 0.125%–0.25% per additional 30 days.
- Do you have rate risk tolerance? Physician incomes are strong enough that most attendings can absorb modest payment increases. But if your housing budget is tight relative to your DTI, rate exposure is a bigger risk than for someone with more payment flexibility.
The Practical Ask
When you're comparing lenders for a physician construction loan, add these questions to your list:
- Is this program OTC or two-close?
- What is your rate lock period, and what does an extended lock cost?
- Do you offer a float-down, and what are the specific trigger terms?
- What are your extension fees if the build runs past the lock expiration?
- What has your average conversion timeline been in the last 12 months?
The answers will tell you more about how the lender actually manages rate risk than any marketing material will.
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MedPharmaConnect is an educational resource, not a lender or financial advisor. For guidance specific to your situation, consult a construction loan specialist or financial advisor with experience in medical professional borrowers.
MedPharmaConnect is an educational resource, not a lender. Always verify program details, current rates, and eligibility with licensed mortgage professionals.