Buying a home in Clayton? You may not see or smell radon, but it can affect your health and your purchase. You want clarity on risk, simple steps to test, and straight answers on what to do if levels come back high. In this guide, you’ll learn how radon testing works in Missouri transactions, what results mean, common negotiation paths, and what mitigation typically costs. Let’s dive in.
Why radon matters in Clayton
Radon is a naturally occurring radioactive gas that can build up indoors and is a leading cause of lung cancer after smoking. Testing is the only way to know indoor levels. Missouri’s radon program reports radon has been measured in every county, and roughly one-third of tested homes in Missouri come in at or above the EPA action level.
Clayton sits within the St. Louis region, where many areas have elevated radon potential. Because levels vary home to home, you should plan to test as part of your due diligence rather than rely on neighborhood reputation. To explore statewide patterns, you can review the MDHSS Radon Dashboard.
Missouri rules and disclosures
Missouri does not require sellers to test for or fix radon as a condition of sale. That said, sellers must disclose what they know. Known radon test results or known radioactive or hazardous contamination are considered material information and should be provided to buyers. You can review guidance from MDHSS and the state statute on disclosure of known contamination in Missouri law.
What to request from sellers
- Copies of any prior radon test reports and lab results.
- Documentation for any mitigation system: installer, system type, and post-install test results.
- Any warranty or guarantees tied to a past mitigation.
How testing works in a purchase
Most real estate transactions in Missouri use a professional short-term test that runs 2 to 7 days. MDHSS advises using certified professionals for transaction testing and following closed-house protocols for accuracy. Learn more about test types and placement from Missouri’s testing guidance.
Professionals often use continuous radon monitors, which measure levels hourly and help validate closed-house conditions. These devices provide detailed reports suitable for negotiations. You can also consult the EPA’s overview of testing resources in its radon publications library.
Interpreting results
- The EPA recommends fixing the home at 4.0 pCi/L or higher and considering mitigation between 2.0 and 4.0 pCi/L. See the EPA’s radon guidance.
- If a short-term test is elevated, retest or complete a longer test to confirm before making final decisions.
- After mitigation, retest to verify the system is working as intended.
Fixing elevated radon
The most common solution is active soil suction (also called sub-slab depressurization). A contractor installs PVC piping and an in-line fan to vent soil gases above the roofline. Properly designed systems often reduce radon by 50 to 99 percent. The EPA explains system performance and follow-up testing in its guide on verifying mitigation.
Costs vary by home size and construction. Missouri guidance notes many straightforward systems come in under $2,000, with broader national ranges around $800 to $2,500. Most systems install in one to two days. The EPA offers a helpful summary of mitigation costs and notes that fans draw modest electricity and may need replacement over time.
Choosing a contractor
- Use certified radon professionals (NRPP or NRSB) and ask for proof of certification and insurance.
- Request references, written scope, and before-and-after test results.
- Ask for a clear warranty and guidance on retesting.
To get started, review the EPA’s guidance on finding qualified radon service providers and the NRSB’s directory.
Buyer checklist for Clayton
- Include radon testing in your inspection period. The St. Louis region has elevated potential, and testing confirms your risk. See the MDHSS radon program.
- Specify professional testing in your contract. MDHSS recommends certified testers for legal transactions. Review state testing guidance.
- Request seller records. Ask for prior test results, mitigation documents, and any post-install tests.
- Plan your negotiation path if results are ≥ 4.0 pCi/L. Options include seller-paid mitigation, a credit, a price adjustment, or an escrow holdback.
- Verify results after mitigation. Require a professional post-mitigation test and get the report in writing. See the EPA’s advice on post-install verification.
- For new builds, consider radon-resistant features. These are low-cost during construction and validated by testing before closing. Learn more about radon-resistant new construction.
- After move-in, retest every couple of years or after major renovations. MDHSS often shares test-kit programs and guidance at the state radon site.
Negotiation options that work
Because Missouri does not require sellers to fix radon, it is important to set expectations in writing. Common outcomes include a seller-installed mitigation system before closing, a buyer credit to install after closing, a price reduction, or an escrow holdback until post-mitigation results are confirmed. Your agent can help you align the approach with your timeline and leverage, while your tester provides the documentation needed for the file. Review state context at the MDHSS radon page.
The bottom line
Radon is manageable when you plan for it. With professional testing, clear contingency language, and proven mitigation methods, you can move forward with confidence in Clayton. If you want a straightforward plan for testing, negotiations, and timing, connect with The Lottmann Group for local guidance tailored to your purchase.
FAQs
Is radon testing required before buying a home in Clayton, MO?
- No. Missouri does not require testing or mitigation, but buyers commonly include a professional test as a contingency, and sellers must disclose known results. See MDHSS guidance.
How accurate is a short-term professional radon test during a purchase?
- Short-term tests (2 to 7 days) are reliable for transactions when closed-house protocols are followed and certified professionals use approved devices like continuous monitors. See state testing guidance.
What do my radon results mean if they are near 4.0 pCi/L?
- The EPA recommends fixing at 4.0 pCi/L or higher and considering mitigation between 2.0 and 4.0 pCi/L. Follow-up testing helps confirm decisions. See the EPA radon page.
How much does radon mitigation typically cost in Missouri homes?
- Many straightforward systems come in under $2,000 in Missouri, with broader ranges around $800 to $2,500 depending on the home. Learn more about mitigation costs.
How quickly can elevated radon be fixed and verified?
- Most systems install in one to two days, and post-install testing verifies performance soon after. See the EPA’s guidance on verifying mitigation.
