Lock the payment you can live with, not the headline you hope for

A rate lock is a temporary contract. The lender agrees to honor a rate, a point structure, and a lock length if you close inside that window. Floating means you have not signed that contract. You still have the chance of a cheaper payment and the chance of a payment that no longer works. The useful decision is not "where will rates be on Thursday." It is whether this house still gets bought if the quote is a quarter to a half point worse.

Nobody reliably forecasts two weeks of mortgage pricing. The 10-year Treasury and the mortgage-Treasury spread both move, and your file still sits on top of that. Treat market commentary as context. Write the lock rules before inspection week, when you still have the patience to do arithmetic.

Lock length is the first number, not the rate

Common lock windows are 15, 30, 45, and 60 days. Start with the close date in the contract, then add the delays that actually happen: a late appraisal, a title defect, a repair that has to be re-inspected. A 15-day lock on a 30-day close is optimism. Extensions usually cost money or a worse rate. Ask for that cost in writing before you pick the shorter, cheaper-looking lock.

Some lenders will not lock until there is a property address. Others sell an extended lock for a fee or a slightly higher rate while you still shop. That fee belongs on a Loan Estimate, not in a phone quote. Compare two locks only if they share the same number of days, the same points or credits, and the same loan amount. A 15-day lock with two points is a different product from a 45-day lock at par.

There is no best weekday. Tuesday versus Thursday is noise for most borrowers. If rates have been falling for a few days, that helps until it reverses. If a 0.25 point drop would not change whether you buy this house, lock and spend the week on inspection. The common failures are locking too short and paying to extend, floating without a written payment ceiling, and ranking two quotes that do not share a lock length.

What a quarter point actually costs on this loan

On a $360,000 loan, a 0.25 percent rate move changes principal and interest by roughly $55 a month, about $660 a year. Over a full 30-year term that is tens of thousands in interest. Most owners do not keep the loan that long. Sell or refinance in five years and the cumulative payment difference is closer to $3,300, not the 30-year total. Decide which number would actually make you walk: the monthly figure, or the multi-year one.

Stress-test three payments on the mortgage calculator: today's quote, plus 0.25 percent, plus 0.50 percent. If the worst of those still fits a month you would recognize, floating is a risk you can take on purpose. If the middle one already forces you to renegotiate price or drop the house, lock. Hope is not a strategy. A pre-written rule is.

Float-downs, extensions, and the rule you write in advance

Ask the lender three things in writing. What does an extension cost, in dollars or rate. Is there a one-time float-down if rates fall after you lock, and what triggers it. What happens if closing slips through no fault of yours: title, repairs, a delayed appraisal. Policies vary widely. A verbal "we can usually help" is not a policy.

Lock when you are under contract, the lock covers the close with slack, a 0.25 to 0.50 point rise would make you renegotiate or walk, and you already have two Loan Estimates at a payment that fits. Keep floating only if you are still months from a contract and a long lock would cost more than it is worth, or you wrote a ceiling in advance and will lock the hour the quote hits it, or the lender offers a written float-down so a later dip is not lost if you lock today.

Pair the decision with what actually moves mortgage rates so a Fed headline does not become a lock panic, and with how to read a Loan Estimate so you are locking a real offer, not a phone number. Current backdrop is on the market page.

Write the ceiling before the inspection report arrives

The worst time to invent a lock rule is the evening a repair credit and a rate quote land in the same hour. Decide the ceiling while the contract is still new. If a quarter point would make you renegotiate price or walk, lock as soon as the lock length covers the close with a few days of slack. If a half point still leaves a payment you would recognize, you can float, but only with the ceiling written down and a person who will lock the hour the quote hits it. Hope that next Thursday is kinder is not that rule.

Ask three things in writing before you choose the cheaper-looking short lock. What an extension costs, in dollars or in rate. Whether a one-time float-down exists if rates fall after you lock, and what triggers it. What happens if title, a re-inspection, or the appraisal slips the close through no fault of yours. A 15-day lock on a 30-day close is optimism. Compare two locks only when the days, the points, and the loan amount match. There is no best weekday. Tuesday versus Thursday is noise next to a lock that expires before the county will record.

On a $360,000 loan, a quarter point is about $55 a month. Over five years that is roughly $3,300, not the thirty-year interest total. Use the horizon you will actually keep the loan. Then go back to inspection. The bond market context, if you want it, is in what actually affects mortgage rates. It will not pick the lock for you.

Sources: CFPB Loan Estimate, CFPB on rate locks. Educational only. Lock fees and float-down rules are lender-specific.