The short answer
If your loan program or lender requires a radon report, the lender wants it in the file before closing. Radon testing cannot be rushed: there is a minimum measurement period of a few days, plus lab analysis and reporting, and if any result comes back at or above 4.0 pCi/L, you add mitigation and a confirmation retest. Those steps are sequential, so a report ordered late in due diligence is the single most common cause of a radon-related closing delay. Confirm whether your program requires testing, then order it early enough to absorb a high result without moving your closing date.
Table of contents
- 1. Why a radon report sits on the critical path
- 2. Whether your loan program requires it
- 3. The measurement window you cannot compress
- 4. What happens when a result comes back high
- 5. Lenders want the documentation in the file
- 6. Building radon into the due diligence timeline
- 7. The mistakes that cause avoidable delays
- 8. Why this hits harder in metro Atlanta
- 9. Frequently asked questions
1. Why a radon report sits on the critical path
Most environmental items in a commercial or multifamily transaction can be ordered and delivered on a flexible schedule. A radon report is different because part of it is a physical measurement that takes a fixed amount of time. You cannot pay to make the air in a building register radon faster. The device has to sit for a minimum period, the sample has to be analyzed, and only then does a written report exist.
For investors, brokers, and acquisition teams, that turns radon into a critical-path item the moment a lender makes it a closing condition. Everything that depends on the completed report sits behind it. If the report is missing or late when the lender assembles the file, the closing waits. If a result is elevated, the work needed to fix it waits on top of that. The delay is rarely about the report being hard to produce. It is about the sequence of steps not fitting into the days that are left.
2. Whether your loan program requires it
The first question is not how to test, it is whether testing is required at all for your specific deal. Some federal loan programs and many lenders build radon into the environmental review, while others leave it to an environmental professional's judgment or to state and local law. The scope, meaning how much of a property is sampled, depends on the loan program and the lender's current guide, and those guides are updated periodically.
Because the answer drives your entire timeline, get it in writing early. Ask your lender directly whether radon testing is a condition of the loan, what protocol they expect the testing to follow, and how broad the sampling needs to be for your property. For background on how the major federal channels handle radon, our guides on HUD multifamily radon requirements and the 2025 Fannie Mae and Freddie Mac radon changes explain how requirements differ by program. Treat them as orientation, not as the final word for your loan.
3. The measurement window you cannot compress
Short-term radon testing requires devices to stay in place for a minimum measurement period of a few days under controlled conditions, and then the samples go to a lab for analysis before a written report can be issued. That sequence is fixed. No amount of urgency shortens the time a device needs to collect a valid measurement or the time a lab needs to analyze and report it.
Add up the real steps: scheduling and device placement, the minimum measurement period, retrieval, lab analysis, and report writing. On a larger property, just planning and staging the placement takes time before the measurement clock starts. Counting only the days a device sits in the building underestimates the true turnaround.
The practical takeaway is to plan the report in weeks, not days, once scheduling and reporting are included. A property with many units or buildings takes longer to stage and to coordinate around tenants, which extends the front end of the process even before the measurement period begins.
4. What happens when a result comes back high
The widely used radon action level is 4.0 pCi/L. A result at or above that level generally means mitigation is required, and the work is not considered complete until a post-mitigation retest confirms the building reads below the action level. That confirmation retest is another measurement period, so an elevated result does not add a day, it adds a second full cycle on top of the first.
This is where most genuine closing delays come from. If testing was ordered with no slack in the schedule and a result comes back high, there is no time left to install a mitigation system and run a confirmation retest before the closing date. The deal either extends or the parties scramble. The way to avoid it is not to hope for low results, it is to leave enough room in the timeline that an elevated result can be handled without moving the date.
5. Lenders want the documentation in the file
A radon report is not just a result, it is a document the lender needs in the loan file before closing. When a program requires testing, the file is not complete without a report that follows the expected protocol and, where mitigation was needed, documents the level found, the system installed, and the post-mitigation results. A verbal "it passed" does not close a file. The written, defensible report does.
That is why a result that is technically fine can still delay a closing if the report is late. The information existing in someone's inbox is not the same as the documentation sitting in the lender file. Build the reporting step into your timeline as its own line item, separate from the measurement period, so the document is in hand and in the file well before the closing date.
6. Building radon into the due diligence timeline
The fix is mostly about sequencing. Treat radon as one of the first environmental items you trigger after going under contract, not one of the last. When testing starts early in due diligence, the measurement period, the lab turnaround, and a contingency window for possible mitigation and a retest all fit inside the due diligence period instead of colliding with the closing date.
A simple way to schedule backward from closing: count back the reporting time, then the measurement period, then a contingency window large enough for mitigation and a confirmation retest, then scheduling and staging. The date you land on is when testing needs to begin. If that date has already passed, you are on the critical path and should start immediately.
A radon professional who works on commercial and multifamily properties can help you map this sequence to your specific building and closing date, including how long staging a larger property realistically takes. The goal is for the report to be finished and in the file with room to spare, so radon never becomes the reason a closing slips.
7. The mistakes that cause avoidable delays
Most radon-related closing delays trace back to a handful of avoidable assumptions. The first is assuming radon testing is not required and finding out late that it is. The second is ordering testing near the end of due diligence, which removes the slack needed to handle an elevated result. The third is counting only the days the device sits in the building and forgetting the scheduling, lab, and reporting steps that bracket the measurement period.
A fourth is using the wrong kind of test. A defensible report for a lender follows a recognized measurement protocol; a generic home test kit picked up at a hardware store will not satisfy a commercial loan file, and discovering that late means starting the real test over. Each of these is easy to avoid with one early conversation with your lender and one with a radon professional, and each is expensive to discover with days left before closing.
8. Why this hits harder in metro Atlanta
Georgia has no state radon testing law, which leads some acquisition teams to assume radon is not a local concern. For a financed deal, that assumption is risky twice over. First, a federal loan program or a lender can require testing regardless of state law. Second, much of metro Atlanta sits in higher-radon EPA zones, with several core counties in Zone 1, the highest category, driven by the region's granite-rich bedrock.
The EPA zone map predicts averages by county; it does not tell you whether a specific building is elevated, and EPA advises testing in any zone. A higher-zone county is not a guarantee of high radon, and a lower zone is not a guarantee of safety. The only way to know a building is to test it.
Put those two facts together and the lesson for an Atlanta-area transaction is to treat elevated results as common enough to plan for rather than as a remote possibility. Building the testing timeline into your due diligence, with room for mitigation and a retest, is what keeps a high reading from turning into a closing delay.
9. Frequently asked questions
This article is general information for property owners, investors, and acquisition teams, not legal, financial, or engineering advice. Loan program requirements, measurement protocols, and lender policies change over time and vary by transaction. Confirm the current requirements that apply to your deal with your lender and a qualified radon professional before making decisions.
