You signed a contract on a new build in Midlothian. The builder rep said November. Your lender wrote a 90-day lock. Then the trusses came late, the inspector backed up, and your walk-through moved to January. The house is still coming. The rate you locked is not — not for free, anyway. Somebody is about to hand you a price to keep it, and most buyers in Ellis County never see that bill coming until it lands.

Direct answer: what happens when a Midlothian build outruns your rate lock

When a Midlothian new construction closing slips past your rate lock expiration, you have three paths: pay a lock extension fee, pay for a longer lock upfront when you first lock, or re-lock at whatever the market gives you that day. Extensions are typically priced as a percentage of the loan amount and they cap out. Once the cap hits, your protected rate is gone.

What a rate lock actually protects on a to-be-built home

A rate lock is a promise from the lender to honor a specific interest rate and specific pricing for a specific number of days. That is the whole thing. It does not protect your closing date, your builder's schedule, or your appraisal. It protects a number, on a calendar, for a set window.

On a resale purchase, that window is easy. You go under contract, you close in 30 to 45 days, a 45-day or 60-day lock covers you with room left over. New construction breaks that math. On a to-be-built home in Midlothian, the gap between contract and closing is often six to nine months. On a spec home that is already framed, it might be 60 to 120 days. Either way, you are locking against a completion date that the builder controls and can revise.

Here is the part buyers miss. Builder contracts almost never guarantee a completion date. They give an estimate, then they give themselves language covering weather, labor, materials, and municipal inspection delays. Your lock has no such language. Your lock has a hard expiration timestamp. One document is flexible and one is not, and they are pointed at the same closing table.

The Midlothian timeline that breaks a 90-day lock

Run the sequence the way it actually happens.

1. You sign in August on a to-be-built in a Midlothian community off FM 663 or US-287. The builder rep pencils in a November completion.
2. The builder's preferred lender writes you a 90-day lock. That covers you through roughly mid-November. On paper it fits.
3. September brings rain. Slab pour moves two weeks. Framing moves with it.
4. October brings a backlog at the city for rough-in inspections. Another two weeks.
5. The builder issues a revised completion: mid-January. That is a nine-week slip from the original estimate.
6. Your lock died in November. You are now 60-plus days past expiration on a house that is not finished.

A nine-week slip is not a disaster story. It is an ordinary quarter in DFW homebuilding. The problem is not the slip. The problem is that the 90-day lock was written to match a date nobody was obligated to hit.

What a rate lock extension costs

Extension pricing is set by each lender and each investor behind that lender, so treat every figure below as typical and illustrative. Your lender's rate sheet is the only one that counts.

Published ranges vary, and they run higher than most buyers assume. AmeriSave's rate lock guide puts a 15-day extension at roughly 0.125% to 0.375% of the loan amount — about $500 to $1,500 on a $400,000 loan. Real Cost Report's rate lock cost guide puts total extension cost at 0.25% to 1% of loan principal, or roughly $1,000 to $4,000 on a $400,000 balance, and notes that lender policies are not uniform — some publish a flat dollar charge for a 60- to 90-day lock while others price in basis points added to the rate. Read the wide end of those ranges, not the narrow end, when you are budgeting.

Put Midlothian numbers on it. Midlothian's median new construction sale price was $574,990 as of July 2026 according to Jome's Midlothian new home data. Take a $560,000 purchase with 20% down as a round working example. That is a $448,000 loan. Here is what extension pricing looks like at that size and at two nearby loan amounts, calculated at the lower end of the published ranges above.

Loan amount	15-day extension at 0.125%	30-day extension at 0.25%	60 total days of extensions (0.5%)	Top of published range (1%)
$400,000	$500	$1,000	$2,000	$4,000
$448,000	$560	$1,120	$2,240	$4,480
$500,000	$625	$1,250	$2,500	$5,000

Illustrative example only. The table is arithmetic run at the low end of published percentage ranges. It is not a quote, not an offer of credit, and not a representation that any lender will price your extension at these figures. At the top of the published ranges the same extensions cost roughly three times as much. Actual extension pricing depends on your lender, your loan program, your loan amount, and market conditions on the day you ask.

Notice what a nine-week slip costs. Four 15-day extensions on a $448,000 loan runs about $2,240 at the low end of published pricing, and closer to $6,700 at the top of it. That money is usually collected at closing as a pricing adjustment, which means it does not feel like a bill. It feels like a slightly worse line on your final disclosure. Buyers sign it because the alternative is losing the rate entirely, and by January they are emotionally and financially committed to the house.

Extended locks paid upfront versus extensions paid later

There is a second way to price this, and the builder's lender may or may not put it in front of you.

Extended rate lock programs are built specifically for new construction. One published example, Fidelity Bank's extended rate lock program, offers terms of 60, 90, 120, 180, 270, and 360 days, secures the lock with an upfront fee, and applies the full fee toward closing costs when the loan closes. Upfront fees on the longer terms commonly land in the low thousands of dollars — a few thousand is a reasonable planning figure — but no lender publishes a standard schedule, so that number is not a quote and has to come from your own lender in writing. Programs also differ on refundability: some credit the entire fee back at closing, some credit part, and some treat part of it as non-refundable.

So you are choosing between two shapes of the same cost.

Approach	When you pay	Typical cost shape	Where it fits
Short lock (60–90 days) plus extensions as needed	At closing, in pieces	~0.125%–0.375% of loan per 15 days added	Spec home already drywalled with a short, credible runway
Extended lock (180–360 days) paid upfront	At lock, refundability varies by program	Commonly a few thousand dollars on longer terms; lender-specific	To-be-built home where the completion estimate is six-plus months out

On our $448,000 example, 60 days of extensions at the low-end 0.125% per 15 days lands near $2,240, and at the high end of published pricing it lands closer to $6,700. Say a long extended lock runs $3,500 upfront. Against the low end it costs more on paper. But the extended lock buys you 180 or 270 days of certainty instead of the sensation of feeding quarters into a meter every two weeks while you watch a framing crew. If the build slips twice, the extended lock is usually the cheaper of the two. If it slips once by three weeks, the short lock plus one extension wins.

That decision is made in month one, not month five. By the time the slip is real, the extended lock option is behind you.

What a float-down actually gets you

A float-down is the option to move your locked rate down if the market improves before closing. Pricing is entirely lender-specific. Some lenders build a limited float-down into the program at no separate charge; others price it as a fee, and around 0.25% of the loan amount is a commonly cited structure, which would be about $1,120 on a $448,000 loan. Ask what yours costs before you assume either one. It is never automatic.

Read the terms before you assume it saves you. Most float-down options come with real limits:

• A trigger threshold. Rates usually have to improve by a stated minimum before the option activates. A drop of 0.10% often does nothing.
• One use only. Most float-downs fire once. If you use it in October and the market improves again in December, you get nothing more.
• A window. The option often has to be exercised a set number of days before closing, which is a problem when your closing date keeps moving.
• It does not extend anything. A float-down changes your rate. It does not add a single day to your lock period.

That last point is the one that costs Midlothian buyers money. Some buyers buy a float-down thinking they bought protection. They bought the upside, not the calendar. If the build slips, the float-down expires with the lock.

For context on where the market sits, the 30-year fixed averaged 6.67% for the week of August 13, 2026, down from 6.69% the prior week and up from 6.58% a year earlier, per the Freddie Mac Primary Mortgage Market Survey. That is a market moving in small increments, not large ones. Small increments are exactly the environment where a float-down threshold never gets tripped.

When extensions cap out and you re-lock at market

Extensions are not infinite. Lenders cap how many extension days you can stack before they require a full re-lock, and 60 additional days is a common ceiling — but that cap is set in each lender's own policy, is not standardized across the industry, and is not something you should assume. Get yours in writing. Short locks carry caps too, and they are usually tighter. Fidelity Bank's published guidance, for example, states plainly that if the lock expires during construction it re-locks at current market rates; the original rate does not carry over.

When the cap hits, your protected rate is finished. You re-lock at current market pricing — whatever that is on the day the builder finally calls for a closing date. That is not a fee you can budget for. It is a repricing.

Here is what that repricing does to a payment on our example loan. Principal and interest only, 30-year fixed, $448,000 loan.

Rate	Monthly principal and interest	Difference vs. 6.67%	Extra cost over 5 years
6.25%	$2,758	-$124	-$7,412
6.67%	$2,882	—	—
6.92%	$2,957	+$75	+$4,475
7.17%	$3,032	+$150	+$8,997
7.42%	$3,108	+$226	+$13,562

Illustrative example only. These are calculated payments on a hypothetical $448,000 loan, 30-year fixed, assuming 20% down, at the interest rates shown. The rates shown are interest rates, not annual percentage rates. An APR would be higher because it also reflects certain loan costs. They exclude property taxes, homeowners insurance, mortgage insurance, HOA dues, and any PID or MUD assessment. Your actual payment will differ. No rate, payment, or down payment figure in this post is a quote, an offer of credit, a representation that any rate is available to you, or a prediction of where rates go.

Compare the columns. A $2,240 extension bill looks expensive until you set it next to a half-point repricing that adds roughly $150 a month for as long as you hold the loan. On a five-year hold that gap is close to $9,000. Over a full 30-year term it is roughly $54,000. The extension is almost always the cheaper outcome, which is exactly why lenders can charge for it.

Why the builder's preferred lender structures locks the way it does

None of this is a conspiracy. It is incentives working the way incentives work.

The builder's sales rep is paid by the builder. Their job is to sell that builder's inventory at that builder's terms. The builder's preferred lender is frequently an affiliated business or an in-house lending arm of the same parent company. Their job is to capture the loan. Both of those people are professionals and many of them are good at what they do. Neither one of them is assigned to protect your lock calendar.

Three structural reasons the short lock keeps showing up:

• Short locks price better. A 90-day lock quotes at a better rate than a 180-day lock, every time. The number in the design center brochure looks stronger with the short lock attached to it. That is the number that helps close the sale.
• Incentive dollars stretch further. Builder credits for closing costs or rate buydowns are usually only usable with the preferred lender. Those credits go further against a cheaper short lock than against an expensive extended one, which makes the whole package look better on the day you sign.
• The completion date is an estimate on their side and a deadline on yours. The builder writes the schedule and reserves the right to revise it. The lock is written against that schedule by a lender who has no control over it. When the two disagree, only one of them charges you.

You are also not required to use the builder's lender to buy the home. You may forfeit builder incentives if you go elsewhere, and sometimes those incentives are worth more than what a shopped rate saves you. Sometimes they are not. That comparison is arithmetic, and it should be run in writing before you sign anything — not after the lock expires.

"The builder rep works for the builder, and so does the builder's lender. Nobody in that transaction is watching your lock calendar unless you bring someone who does. I look at the contract date and the lock date as one plan, because they are." — Steven J. Thomas, Broker at Refind Realty DFW and Loan Officer at Envision Home Lenders, NMLS #689220

Where Midlothian buyers are running into this

Communities and builders active in Midlothian

Midlothian sits in Ellis County along US-287, roughly 30 miles south of downtown Dallas and a similar reach toward Fort Worth. Growth here has been steady enough that dozens of builders are working the market at once, and a large share of the available homes are to-be-built contracts rather than finished inventory — which is exactly the situation where lock timing becomes a live issue.

According to Jome's Midlothian community data, the most active builders in Midlothian include John Houston Homes, Bloomfield Homes, First Texas Homes, Perry Homes, and Highland Homes, with David Weekley Homes also active in the area. Community names that come up repeatedly include Hayes Crossing, Mockingbird Heights, Villages of Walnut Grove, Ridgepoint, Parkside North, and Redden Farms.

Every one of those builders sets its own schedule language, its own preferred lender relationship, and its own incentive structure. Two contracts in two neighboring Midlothian communities can carry completely different lock exposure. Read yours, specifically. General reference on the region is on the DFW new construction homes hub.

Midlothian market context, based on current conditions

• Median new construction sale price: $574,990 as of July 2026 (Source: Jome, July 2026)
• Median sale price, all home types: approximately $484,000 for the three months ending June 2026, down about 1.4% year over year, with a median 70 days on market (Source: Redfin Midlothian housing market, June 2026)
• 30-year fixed average: 6.67% for the week of August 13, 2026, versus 6.69% the prior week and 6.58% a year earlier (Source: Freddie Mac PMMS, August 13, 2026)

Prices in that range put most Midlothian new construction buyers in loan amounts between roughly $380,000 and $500,000 depending on down payment. That is the loan size where a half-point repricing stops being an abstraction and starts being a car payment.

Costs a Midlothian new construction buyer should budget beyond the base price

Lock exposure is one line in a larger stack. Ranges below are typical for DFW new construction and vary by builder, community, and lot. Confirm every one of them in writing on your specific contract.

• Lot premium: commonly several thousand dollars for greenbelt, corner, or cul-de-sac positions
• Design center selections: the single most common budget overrun on a to-be-built home
• Earnest money and design deposits: builder-specific, and frequently non-refundable once selections are made
• PID or MUD assessments: some newer communities carry them; they show up on the tax bill, not the sales sheet
• Rate lock extensions or an extended lock: the subject of this post, and the one nobody puts on the worksheet
• Temporary housing: if you sold first and the build slips, this is the cost that stacks on top of everything else

Add those together before you decide how much house you are comfortable buying. A build that slips two months can move three of those six lines at the same time.

Questions to ask before you sign the builder contract

1. What lock terms does this lender offer, in days, and what does each one price at today?
2. What does an extension cost per 15 days, stated as a percentage of the loan amount?
3. How many total extension days are allowed before a full re-lock is required?
4. If a re-lock is required, is it at current market or at worse-case pricing?
5. Does a float-down exist, what does it cost, what is the improvement threshold, and how many times can it be used?
6. What is the builder's written completion estimate, and what contract language lets them revise it?
7. What is the total dollar value of the builder incentive, and what happens to it if I use a different lender?
8. Who notifies me when the lock is approaching expiration, and how many days of warning do I get?

Get the answers in writing, in the same email thread, dated. If a lender will not put extension pricing in writing before you lock, that is your answer about how the extension conversation will go in month four.

How to structure the lock and the contract as one plan

The fix is not complicated. It is just early.

Start by pricing the lock against the builder's realistic completion window plus a buffer, not against the optimistic estimate on the sales sheet. If the builder says November on a slab that has not been poured, plan for January. On a to-be-built home six-plus months out, price the extended lock and compare it against the likely extension stack. On a spec that is already drywalled with a credible 60-day runway, the short lock plus a possible extension usually wins.

Then put the lock expiration date on the same calendar as the contract milestones — slab, frame, drywall, trim, final inspection. When a milestone slips, you know immediately what it did to the lock instead of finding out from a pricing adjustment at the closing table. That is the entire reason to have someone licensed on both sides of the transaction reading both documents. The contract date and the lock date are one plan, and treating them as two separate problems is what costs Midlothian buyers thousands of dollars.

More background on the process is in the new construction buyer guide.

Takeaways for Midlothian buyers

• A rate lock protects a number on a calendar. It does not protect your closing date, and builder completion estimates are estimates, not obligations.
• Published ranges put a 15-day extension at roughly 0.125% to 0.375% of the loan amount, and total extension cost at 0.25% to 1% of loan principal. On a $448,000 Midlothian loan, that is roughly $560 to $1,680 per 15 days in an illustrative calculation, not a quote.
• Extended new construction lock programs run 60 to 360 days, and the upfront fee on longer terms commonly lands in the low thousands of dollars. It is lender-specific, and that decision is made at lock, not at slip.
• A float-down is priced by the lender — sometimes included, often around 0.25% of the loan — typically fires once, requires a threshold move, and adds zero days to your lock.
• Extensions cap out, with 60 cumulative days a common ceiling, and a re-lock at market is the expensive outcome. A half-point repricing on a $448,000 example loan is roughly $150 a month, near $9,000 over five years.

FAQ: Midlothian new construction rate locks

How long should my rate lock be on a Midlothian to-be-built home?

Match it to the builder's completion window plus a buffer for slippage. On a to-be-built contract six or more months out, an extended lock of 180 to 270 days usually fits better than a 90-day lock you will extend three times.

How much does a rate lock extension cost?

Published ranges run roughly 0.125% to 0.375% of the loan amount per 15 days, with total extension cost commonly cited at 0.25% to 1% of loan principal. On a $448,000 loan that is roughly $560 to $1,680 per 15 days as an illustrative calculation, not a quote. Your lender's rate sheet is the only one that counts.

What happens if my rate lock expires before the builder finishes?

You either extend, if extension days remain, or you re-lock at current market pricing. Published extension and re-lock costs have been reported anywhere from 0.125% to 1% of the loan amount, and on a re-lock you also take whatever the market rate is that day. The original rate does not carry over.

Do I have to use the builder's preferred lender in Midlothian?

No. You may forfeit builder incentives tied to that lender, so run the comparison in writing before deciding. The incentive is sometimes worth more than a shopped rate and sometimes it is not.

Is a float-down worth paying for on a new build?

Only if you understand the limits. Cost is lender-specific — some programs include a limited float-down at no separate charge, others price it around 0.25% of the loan. It usually fires one time, requires rates to improve past a stated threshold, and does not extend your lock by a single day.

What are rates doing right now?

Freddie Mac's Primary Mortgage Market Survey put the 30-year fixed average at 6.67% for the week of August 13, 2026, compared with 6.69% the prior week and 6.58% a year earlier. Rates change weekly and past readings do not predict future ones.

The bottom line for Midlothian buyers

A Midlothian build slipping from November to January is normal. Paying for it twice is not. The extension bill, the float-down that never triggered, the re-lock at a worse market — all three trace back to a lock that was written against a date nobody was contractually required to hit. That is a planning problem, and planning problems get solved at the beginning.

Steven J. Thomas is licensed on both sides of this — a Broker at Refind Realty DFW and a Loan Officer at Envision Home Lenders, NMLS #689220. That means the builder contract and the lock agreement get read by the same person, against the same calendar, before you sign either one.

Get pre-approved and get your lock strategy mapped to your builder's timeline before you sign: Start your pre-approval here.

This post is general education, not an advertisement for any specific credit product, not an offer to lend, and not a lending commitment. All rate, fee, and market figures reflect conditions as of August 18, 2026, are based on current conditions, and are subject to change. No rate shown is available, offered, or quoted to any reader. Rates shown are interest rates, not annual percentage rates; an APR would be higher because it also reflects certain loan costs. Fee ranges are typical, illustrative, and lender-specific — they are not quotes, and your lender's actual pricing may fall outside them. Payment figures are hypothetical example calculations on a $448,000 loan assuming 20% down and a 30-year fixed term; they exclude taxes, insurance, mortgage insurance, HOA dues, and PID or MUD assessments, and your actual payment and terms will differ. Nothing in this post is a guarantee of rate, price, timeline, savings, loan approval, or outcome. Pre-approval requires a full application, is subject to underwriting review, and does not commit any lender to make a loan. Steven J. Thomas — Broker, Refind Realty DFW, and Loan Officer, Envision Home Lenders, NMLS #689220. 128 S. Cockrell Hill Rd, DeSoto, TX 75115. 972-846-9170. Equal Housing Opportunity. Equal Housing Lender. Information deemed reliable but not guaranteed. Texas Real Estate Commission Information About Brokerage Services and Consumer Protection Notice available at stevenjthomas.com.