Do Homes Without Basements Need Radon Testing?
Many homeowners assume radon is only a basement problem. If your home sits on a concrete slab, over a crawl space, or has a split-level layout, it is easy to think radon testing does not apply to you. The reality is that radon can enter almost any type of home. Here is what homeowners in Green Bay, Appleton, and across Wisconsin should know about radon in homes without basements.
Can Homes Without Basements Have High Radon Levels?
Yes. Homes without basements can and do have elevated radon levels. The U.S. Environmental Protection Agency states that any home may have a radon problem, including new and old homes, well-sealed and drafty homes, and homes with or without basements.
Radon is a radioactive gas that forms naturally as uranium breaks down in soil and rock. It moves up through the ground and into the air beneath and around your home. Whether that soil gas sits under a basement floor, a slab, or a crawl space, it can find its way inside. A basement may put more of your living space in direct contact with the soil, but it is not what creates radon in the first place.
How Does Radon Get Into a Slab-on-Grade Home?
Radon gets into slab homes through cracks, joints, and openings in the concrete. Common entry points include:
- Cracks in the slab or where the slab meets the foundation walls
- Construction joints and expansion joints
- Gaps around plumbing, utility lines, and floor drains
- Openings around sump pits or other penetrations
Homes also tend to have slightly lower air pressure indoors than in the soil below, especially during the heating season. That pressure difference can draw soil gas up through any available opening, which is why a slab home is not automatically protected.
Are Homes With Crawl Spaces at Risk for Radon?
Yes. A crawl space gives radon a direct path from exposed soil into the space under your floors, and from there into your living areas. Air from the crawl space can move up through gaps around ductwork, plumbing, wiring, and floor joists. In homes where HVAC equipment or ducts are located in the crawl space, that air can be pulled into the rest of the house even more easily.
Construction style is one of several factors that shape how radon behaves in a home. For a closer look at how soil and building type affect radon, see this overview on whether certain areas are more prone to radon.
What About Split-Level Homes and Homes With Multiple Foundations?
Split-level homes and homes with additions often have more than one foundation type, and each one can let radon in differently. A single house might combine a partial basement, a slab-on-grade family room, and a crawl space under an addition. Radon levels can vary between those areas, so one test may not tell the whole story. If your home has more than one foundation type, a radon professional can help decide where testing makes the most sense.
Where Should I Place a Radon Test If I Do Not Have a Basement?
Place the test in the lowest level of your home that is used as living space, which for most slab and crawl space homes is the main floor. The EPA recommends testing in the lowest lived-in level. Avoid kitchens, bathrooms, laundry rooms, and areas near drafts, windows, or exterior doors, since humidity and airflow can affect results. For more detail, our guide on where to place a radon test walks through the best spots in a home.
Short-term tests give a quick snapshot, while long-term testing or continuous radon monitoring shows how levels change over time. If you are deciding between a do-it-yourself kit and a professional test, this comparison of DIY and professional radon testing lays out the differences.
What Radon Level Means I Should Take Action?
The EPA recommends fixing your home if radon levels are 4.0 picocuries per liter (pCi/L) or higher. The EPA also suggests considering mitigation for levels between 2.0 and 4.0 pCi/L, since there is no known safe level of radon exposure. The World Health Organization sets a lower reference level of 2.7 pCi/L.
Radon matters because long-term exposure is the second leading cause of lung cancer in the United States, according to the EPA, and the leading cause among people who do not smoke. The good news is that testing is simple, and elevated levels can be reduced.
How Is Radon Mitigated in a Home Without a Basement?
Radon in slab and crawl space homes is usually reduced with a system that draws soil gas from beneath the home and vents it safely outdoors. The approach depends on the foundation:
- Slab-on-grade homes: Sub-slab depressurization is the most common method. A suction point is installed through the slab, and a radon fan pulls soil gas from under the concrete through a pipe that vents above the roofline.
- Crawl space homes: Sub-membrane depressurization is often used. A durable plastic barrier is placed over the crawl space floor, and a fan draws radon from beneath that barrier and vents it outside.
- Homes with multiple foundations: A system may combine methods to address each area.
Sealing cracks can help a system work better, but the EPA does not recommend sealing alone as a way to reduce radon, because it has not been shown to lower levels significantly or consistently. After any radon mitigation system is installed, the home should be retested to confirm that levels have come down.
How Often Should I Test My Home for Radon?
Test at least every two years, and retest after major renovations, foundation work, or changes to your heating and cooling system. Radon levels can shift over time as a home settles or as its airflow changes. Testing after a mitigation system is installed, and periodically afterward, confirms the system is still doing its job.
Ready To Test Your Green Bay or Appleton Home?
No basement does not mean no radon. Whether your home sits on a slab, over a crawl space, or on a mix of foundations, the only way to know your level is to test. A-1 Radon is NRPP and AARST certified and has helped Wisconsin homeowners with professional radon testing and mitigation for years. Request a radon test today and get clear answers about the air in your home.
