--- title: "Mold Remediation in St. Charles County, MO | Advanced Environmental Services" description: "Mold in a St. Charles County, Missouri home? See why newer houses in O'Fallon, St. Peters and Wentzville grow mold, what the County says, and what to do." url: https://www.aes-stl.com/service-areas/st-charles-county-mo publisher: Advanced Environmental Services phone: +1-314-865-2662 quote: https://www.aes-stl.com/contact --- # Mold remediation in St. Charles County, Missouri: O'Fallon, St. Peters and Wentzville St. Charles County's environmental health division does not perform indoor air testing or assist with mold cleanup. Most homes in O'Fallon and Wentzville are new, so mold there comes from moisture, not age. EPA says to consult its guide when mold covers more than 10 square feet. AES provides mold remediation from St. Louis. [Request a Quote](https://www.aes-stl.com/contact)[(314) 865-2662](tel:+1-314-865-2662) ![Building wrapped in white containment sheeting with an AES storage container in front](https://www.aes-stl.com/_astro/AESI-083.BQiJ3BQs_Z1FKjAJ.webp) ![Aircraft hangar with a yellow fire truck and equipment during an AES PFAS project](https://www.aes-stl.com/_astro/pfas-2025-06-24-11.09.00.CKLsY786_1Qvvzs.webp) ![Worker in an orange lift working on the upper floor of a brick building](https://www.aes-stl.com/_astro/Lead-2.9LKWOFtB_1gAHyw.webp) ## New homes get mold too Only 9.2% of O'Fallon homes and 9.9% of Wentzville homes date before 1980. Moisture, not age, drives mold there. ## The County does not clean mold County environmental health does not do indoor air testing or help with mold cleanup. You hire a contractor. ## The 10 square foot line EPA says to consult its guide when mold covers more than 10 square feet or after a lot of water damage. ## Foundations matter The County says gas can seep in through cracks and gaps in foundations. Water follows the same paths. ## St. Charles County at a glance County role in mold cleanup No indoor air testing and no help with mold cleanup [sccmo.org](https://www.sccmo.org/792/Air-Quality) County homes built before 1980 24.7% [api.censusreporter.org](https://api.censusreporter.org/1.0/data/show/latest?table_ids=B25034&geo_ids=16000US2964082,05000US29183) County housing units counted 172,400 [api.censusreporter.org](https://api.censusreporter.org/1.0/data/show/latest?table_ids=B25034&geo_ids=16000US2964082,05000US29183) O'Fallon homes built before 1980 9.2% [api.censusreporter.org](https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US2954074,16000US2978442,16000US2965126,16000US2964082) Wentzville homes built before 1980 9.9% [api.censusreporter.org](https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US2954074,16000US2978442,16000US2965126,16000US2964082) St. Peters homes built before 1980 25.3% [api.censusreporter.org](https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US2954074,16000US2978442,16000US2965126,16000US2964082) EPA mold size line More than 10 square feet: consult EPA guide [epa.gov](https://www.epa.gov/mold/mold-cleanup-your-home) Office to O'Fallon (100 S. Main St.) About 36.8 miles, 51 minutes without traffic [router.project-osrm.org](https://router.project-osrm.org/route/v1/driving/-90.233935,38.599770;-90.69983649095,38.810942706965?overview=false) Office to St. Charles Main St. About 25.9 miles, 38 minutes without traffic [router.project-osrm.org](https://router.project-osrm.org/route/v1/driving/-90.233935,38.599770;-90.4813,38.7812?overview=false) Home baseAreas we serveSelect an area for its page. Map data: US Census Bureau. ## Does St. Charles County help with mold cleanup? No. St. Charles County’s Division of Environmental Health and Protection says it does not perform indoor air testing or assist with mold cleanup. You can report a concern for mold growth in a county building to your municipality or the County’s Community Development department. Cleanup is up to the owner and a contractor. That matters because many owners call the County first. The answer is a referral, not a crew. If you find mold in O’Fallon, St. Peters, Wentzville or the city of St. Charles, plan to hire a company yourself. AES offers [mold remediation](https://www.aes-stl.com/mold-remediation) and [mold inspection](https://www.aes-stl.com/mold-inspection) from its St. Louis office. ## Why do new homes in O’Fallon and Wentzville get mold? Moisture. Mold needs water, not age. Only 9.2% of O’Fallon homes and 9.9% of Wentzville homes were built before 1980, so these are mostly newer houses. A leak or a wet basement feeds mold in any house. Place Homes built before 1970 Homes built before 1980 O’Fallon 6.1% 9.2% Wentzville 7.7% 9.9% St. Peters 4.7% 25.3% St. Charles County 12.8% 24.7% Place figures are 2024 American Community Survey 5-year estimates. The county row is the 1-year estimate for 172,400 housing units, so compare loosely. St. Peters shows a bigger 1970s share than its neighbors, at 25.3% before 1980. Common causes include a failed supply line, a clogged drain, a roof leak and water that finds its way through the foundation. The fix always starts with the water. Read our guide to [mold after water damage](https://www.aes-stl.com/guides/mold-after-water-damage). ## How big a mold problem needs a professional? EPA draws the line at 10 square feet. It says that if there has been a lot of water damage, or mold growth covers more than 10 square feet, you should consult its guide for larger buildings. Hidden growth, sewage water and repeat outbreaks also call for a pro. Ten square feet is a patch about 3 feet by 3 feet. Measure what you can see. Then look for what you cannot: behind drywall, under carpet pads and around plumbing. Our post on [mold over 10 square feet](https://www.aes-stl.com/blog/mold-over-10-square-feet) explains how to size a patch. A trained crew limits the spread of [mold spores](https://www.aes-stl.com/glossary/mold-spores) with [containment](https://www.aes-stl.com/glossary/containment), cleans the air with a [HEPA filter](https://www.aes-stl.com/glossary/hepa-filter) and removes damaged material. Learn what [mold remediation](https://www.aes-stl.com/glossary/mold-remediation) means in the trade. ## Do basements and foundations matter in St. Charles County? Yes. Water and gas both use the same cracks. The County says radon can become a problem indoors by seeping through cracks and gaps in foundations, drains or other openings. Water finds the same paths, so a damp foundation is a mold warning. We do not have a county figure for how many homes have basements, so we do not claim one. Check your own: look for stains at the base of walls and a musty smell. AES describes its [moisture barrier](https://www.aes-stl.com/glossary/moisture-barrier) as a liquid applied before flooring to prevent moisture from penetrating the floor. See [moisture barriers](https://www.aes-stl.com/moisture-barriers). For water damage, the [fire and water restoration](https://www.aes-stl.com/fire-and-water-restoration) page covers the first steps. ## What does mold remediation cost and how long does it take? AES publishes one range: “Prices typically range between $1500 to $10,000 for a home which is showing visible signs of mold.” AES adds that “1 to 5 days is the normal timeframe expected to complete most average jobs.” Each job differs, so AES quotes by address. Size, material and the water source drive the price. A small bathroom ceiling costs less than a finished basement with wet drywall. See [mold remediation costs](https://www.aes-stl.com/mold-remediation-costs) and our [mold remediation cost and timeline guide](https://www.aes-stl.com/guides/mold-remediation-cost-and-timeline) for the factors. A quote request takes a few minutes at [/contact](https://www.aes-stl.com/contact). ## Should I test for mold first? Usually not when mold is visible. A test helps when you smell mold but cannot find it, or when you want proof a cleanup worked. AES offers [mold inspection](https://www.aes-stl.com/mold-inspection), and our glossary explains [mold inspection](https://www.aes-stl.com/glossary/mold-inspection) in plain terms. Be careful with free test offers and cheap swabs. A result with no plan behind it just starts an argument. Ask what the test will change. If you can see growth over 10 square feet, go straight to a plan, a quote and a fix for the water. For visible black growth, see [black mold remediation](https://www.aes-stl.com/black-mold-remediation) and [home mold removal](https://www.aes-stl.com/home-mold-removal). ## How far is the AES office from St. Charles County? AES works from 3100 Gravois Ave in St. Louis. O’Fallon (100 S. Main St.) is about 36.8 miles away, about 51 minutes without traffic. Main Street in the city of St. Charles is about 25.9 miles, about 38 minutes. These are OSRM free-flow estimates, so allow more at rush hour. AES says it serves St. Louis, St. Charles and Columbia, Missouri, and projects within 300 miles of St. Louis. For the city of St. Charles, including demolition permit steps and asbestos rules, see [St. Charles, Missouri](https://www.aes-stl.com/service-areas/st-charles-mo). For nearby work, see [St. Louis County](https://www.aes-stl.com/service-areas/st-louis-county-mo). ## Which AES services fit a St. Charles County mold job? Mold jobs often need more than a cleanup. A leak must be fixed, wet materials removed and the floor protected. - [Mold remediation](https://www.aes-stl.com/mold-remediation) removes mold-contaminated building materials. - [Mold inspection](https://www.aes-stl.com/mold-inspection) looks for hidden growth. - [Home mold removal](https://www.aes-stl.com/home-mold-removal) covers houses. - [Moisture barriers](https://www.aes-stl.com/moisture-barriers) go under new flooring to prevent moisture from penetrating it. - [Fire and water restoration](https://www.aes-stl.com/fire-and-water-restoration) handles water damage first. AES serves residential and commercial customers. See [commercial mold remediation](https://www.aes-stl.com/commercial-mold-remediation) for larger buildings. ## How do I get a quote? Call (314) 865-2662 or send our [quote form](https://www.aes-stl.com/contact). Give us your city, where you found mold, how big it looks and what caused the water. Photos help. ## Next step Call (314) 865-2662 or use the [quote form](https://www.aes-stl.com/contact) with your St. Charles County address. Start with the [mold remediation](https://www.aes-stl.com/mold-remediation) page. ## Frequently asked questions ### Does St. Charles County help with mold cleanup? No. The County's Division of Environmental Health and Protection says it does not perform indoor air testing or assist with mold cleanup. You can report a concern for mold growth in a county building by contacting your municipality or the County's Community Development department. For cleanup, hire a mold remediation contractor. ### How big can a mold patch be before I need a professional? EPA says that if there has been a lot of water damage, or mold growth covers more than 10 square feet, consult its guide for larger buildings. Sewage water and hidden mold behind walls also call for a professional. Measure the visible growth first, then look for the water source. ### Why does mold grow in new St. Charles County homes? Moisture. Mold needs water, not age. Only about 9.2% of O'Fallon homes and 9.9% of Wentzville homes were built before 1980, yet leaks, wet basements, plumbing failures and high humidity still feed mold. Find and fix the water source, or the mold returns. ### How much does mold remediation cost in St. Charles County? AES publishes this range: prices typically range between $1500 to $10,000 for a home which is showing visible signs of mold, and 1 to 5 days is the normal timeframe expected to complete most average jobs. Each job differs. Request a quote with your address and photos. ### Should I test for mold first? Usually not when you can see it. Testing helps when you smell mold but cannot find it, or when you want to check that a cleanup worked. AES offers mold inspection. Ask us whether an inspection fits your case before you pay for a lab test. ### Does AES serve O'Fallon, St. Peters and Wentzville? AES serves St. Louis and projects within 300 miles. The office at 3100 Gravois Ave is about 36.8 miles from O'Fallon without traffic, and about 25.9 miles from Main Street in St. Charles. Call (314) 865-2662 to confirm your address. ### How do I get a quote? Call (314) 865-2662 or send the quote form at /contact. Tell us your city, where the mold is, how big the patch looks, and what caused the water. Photos help us scope the job. ## Terms on this page - [Moisture barrier](https://www.aes-stl.com/glossary/moisture-barrier) - [Mold remediation](https://www.aes-stl.com/glossary/mold-remediation) - [Mold inspection](https://www.aes-stl.com/glossary/mold-inspection) - [Containment](https://www.aes-stl.com/glossary/containment) - [HEPA filter](https://www.aes-stl.com/glossary/hepa-filter) - [Mold spores](https://www.aes-stl.com/glossary/mold-spores) - [Black mold](https://www.aes-stl.com/glossary/black-mold) ## Sources 1. [St. Charles County: Air Quality](https://www.sccmo.org/792/Air-Quality) 2. [St. Charles County: Air Quality (radon and foundations)](https://www.sccmo.org/792/Air-Quality) 3. [U.S. EPA: Mold Cleanup in Your Home](https://www.epa.gov/mold/mold-cleanup-your-home) 4. [U.S. Census Bureau: ACS 2024 1-year, table B25034 (St. Charles County)](https://api.censusreporter.org/1.0/data/show/latest?table_ids=B25034&geo_ids=16000US2964082,05000US29183) 5. [U.S. Census Bureau: ACS 2024 5-year, table B25034 (O'Fallon, Wentzville, St. Peters)](https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US2954074,16000US2978442,16000US2965126,16000US2964082) 6. [OSRM route estimate: office to O'Fallon](https://router.project-osrm.org/route/v1/driving/-90.233935,38.599770;-90.69983649095,38.810942706965?overview=false) 7. [OSRM route estimate: office to St. Charles](https://router.project-osrm.org/route/v1/driving/-90.233935,38.599770;-90.4813,38.7812?overview=false) Checked against the sources above on November 6, 2026. Rules and fees change, so check the linked page before you act. ## Request your custom environmental remediation estimate Contact us for a free environmental remediation or restoration estimate and a personalized solution to your problems. [Or call (314) 865-2662](tel:+1-314-865-2662)