What a Rate Lock Actually Does

What a lock is

A rate lock is a commitment from the lender to honor the pricing on your file for a defined window, regardless of what the market does inside that window. In exchange, you commit to closing inside it.

That is the whole trade. You give up the upside if the market improves; you are protected if it does not.

I do not publish pricing on this site, so nothing here is a quote. This is about the mechanism.

What it does not protect

This is where people get surprised.

A lock protects the pricing on the file as it exists when you lock it. It does not protect you from changes to the file. If your credit score moves, your loan amount changes, the property type turns out to be different than described, the occupancy changes, or the program changes, the pricing is re-evaluated. That is not a lender being difficult — the original pricing was calculated from those specific inputs.

The practical rule: after you lock, treat your financial life as frozen. Same rule as the credit-during-underwriting guide, and for the same reason.

When the window starts

The day you lock, not the day you go under contract. Locking early means burning window on inspection and appraisal — the two steps most likely to add time.

Which is why the honest sequencing question is not "should I lock now" but "how much of the window do I still need?" Count backwards from your contract closing date and add room for the two or three things that always take longer than expected: a condo questionnaire, an insurance binder in Florida, a title issue nobody saw coming.

What happens if you close late

An extension. Extensions have a cost, and that cost is generally paid by whoever caused the delay — which is usually a negotiation, not a rule. What matters is that the lock expiring is not a catastrophe; it is an expense. Nobody loses the loan because of it.

The version that actually hurts is a lock expiring in a market that moved against you, so you are re-pricing at whatever exists that day. That is the risk being managed.

Float-down

A float-down is an option, usually bought or built into pricing, that lets you take advantage if the market improves meaningfully after you lock. The terms vary a lot: how much of a move triggers it, how many times you can use it, and whether the window resets.

Ask three questions before you assume you have one: does this loan have one, what is the trigger, and what does exercising it cost. "It has a float-down" is not an answer.

Extended locks and new construction

If you are buying new construction with a delivery date months out, a standard lock window does not reach. Extended lock products exist for exactly this, and they price differently because the lender is carrying the risk longer.

If your builder is telling you a delivery month rather than a date, that is a signal to plan the lock strategy at contract signing — not at the walkthrough. Same conversation applies to construction loans.

The one thing to take away

Locking is not a bet you win or lose. It is a decision about how much uncertainty you want to carry between now and closing. People with a firm closing date and no appetite for volatility should lock. People with a soft date and a builder who has slipped twice should talk through the extension math first.

Ask me where your file actually sits before you decide.