Short Answer: Radon enters your home from the soil and rock beneath it, seeping through foundation cracks, sump pits, floor drains, plumbing gaps, and hollow block walls. It can also enter through crawl spaces and be released from private well water. The only way to know if radon levels are high is to test your home.

You cannot see it. You cannot smell or taste it either. Yet right under your floorboards, radioactive gas might be finding its way into the air your family breathes.

This guide reveals how soil gases bypass concrete, where hazards hide, and how radon enters through routes most homeowners never think to inspect.

In late 2016, Rachael Malmberg was an elite athlete in peak physical shape. A former Team USA hockey standout and collegiate star, she went for a routine run and felt sudden pain in her ribs. Weeks later, doctors diagnosed the 31-year-old nonsmoker with stage 4 lung cancer that had spread to her brain.

Confused and searching for answers, she learned about indoor air risks and radon. She tested her Minnesota home, only to find elevated radon levels. Her childhood home tested even higher.

Her experience highlights an important fact: radon exposure can affect people regardless of their age, fitness, or smoking history.

Where Does Radon Come From in Homes

Radon comes from the natural radioactive decay of uranium found in rock, soil, and, in some cases, groundwater. As uranium decays, it produces radium, which eventually decays into radioactive radon gas that moves toward the surface.

Because radon is a gas, it can travel through soil and gravel. Outdoors, it generally disperses into the atmosphere, reducing its concentration.

Trouble begins when this gas encounters your foundation. Instead of dispersing outdoors, it can enter your home and accumulate indoors.

How Does Radon Get into Your Home

To understand how radon gets into your home, you need to understand air pressure. The stack effect can make your living space behave like a chimney. Warm indoor air rises and escapes through upper parts of the house, sometimes lowering air pressure on the lower levels and drawing soil gas inward.

Think of your house as a straw.

When your furnace, clothes dryer, or bathroom exhaust fans operate, they can also change indoor air pressure. Depending on the system and conditions, this can increase the movement of soil gas through foundation openings.

If indoor pressure is lower than the pressure in the surrounding soil, radon-bearing soil gas can move through available gaps. A large opening is not necessary; even small cracks and unsealed penetrations can provide a pathway.

5 Ways Radon Gas Penetrates Your Living Space

Understanding how does radon get into your home means looking beyond obvious foundation damage. The gas can exploit openings you might never think to inspect.

1. Concrete Slab Cracks and Expansion Joints

Hairline cracks in basement floors or slab-on-grade foundations offer potential entry routes. Concrete can develop cracks as it cures, while settling and temperature changes may create or widen them over time.

The joints where basement floors meet foundation walls can also provide pathways for soil gas. These gaps may be difficult to notice but can allow radon to enter.

2. Open Sump Basins and Floor Drains

An uncovered sump pit can provide a direct pathway between the soil beneath your slab and your basement. If the basin lacks a properly sealed, airtight cover, soil gas can enter the home.

Floor drains and drainage systems connected to the area beneath your foundation may also allow gas to enter, particularly when traps are dry or openings are unsealed.

3. Hollow Cinder Block Foundations

Cinder blocks may look solid from the outside, but their cores are hollow.

Radon can enter through porous masonry, cracks, and openings in below-grade block walls. It may then travel upward through hollow cores and escape through gaps at the top of the wall or into adjoining wall cavities.

4. Utility Chases and Plumbing Openings

Plumbing rough-ins beneath tubs and shower pans can leave gaps around pipes.

Contractors also cut openings through concrete slabs to install drain lines, water supplies, gas lines, and electrical conduits. If these penetrations are not properly sealed, soil gas can move around the pipes and enter the living space.

Other overlooked pathways include construction joints, gaps behind wall finishes, and openings around suspended floors above crawl spaces. Homes with exposed soil in crawl spaces may also allow radon to enter through the floor above.

5. Private Well Water

Soil is not the only source to consider. Groundwater can absorb radon as it moves through uranium-bearing rock.

When you shower, wash dishes, or do laundry, dissolved radon may be released from the water into indoor air. For most homes with elevated indoor radon, soil gas entering through the foundation is the more important source. 

The principal established concern from radon in household water is inhalation of gas released into indoor air, although ingestion can present a smaller potential risk.

If you use a private well and suspect that water contributes to indoor radon, consider having the water tested.

How Can You Tell if Radon Is Leaking In

You cannot tell whether radon is entering your home by sight, smell, or taste. Testing with an appropriate radon test kit or a qualified testing professional is the only reliable way to determine your indoor radon concentration.

The U.S. Environmental Protection Agency (EPA) estimates that radon causes about 21,000 lung cancer deaths annually in the United States. It is the leading cause of lung cancer among nonsmokers and the second-leading cause overall.

If testing reveals levels at or above 4.0 picocuries per liter (pCi/L), the EPA recommends taking steps to reduce radon. Levels between 2.0 and 4.0 pCi/L also warrant consideration of mitigation because no radon exposure level is known to be entirely risk-free.

Protecting Your Living Space from Soil Gas Infiltration

Fixing high radon levels starts with understanding how does radon get into your home and identifying the pathways involved. Sealing visible cracks and covering sump pits can help, but these measures alone rarely solve a significant radon problem.

Many homes require an active soil depressurization system. A vent pipe and fan draw radon-bearing soil gas from beneath the foundation and discharge it outdoors, usually above the roofline, where it can disperse.

After mitigation, retesting is essential to confirm that radon levels have fallen and the system is working effectively.

Stop guessing about the air inside your living spaces. TexInspec delivers thorough, professional home inspections and environmental testing to help you understand your property’s condition. Contact us to learn about the appropriate testing services for your home and take an informed step toward safer indoor air.

FAQs

1- Can new construction homes have high radon levels?

Yes. New homes can have elevated radon levels, just like older homes. Construction age, insulation, and airtightness alone do not determine radon concentration. Local geology, foundation design, soil conditions, and ventilation all play a role.

2- Can you get rid of radon permanently just by opening windows?

No. Opening windows may temporarily reduce indoor radon concentrations, but levels can rise again when windows close. Changes in weather, ventilation, and indoor air pressure can affect how much radon enters your home. A properly designed mitigation system is a more reliable long-term solution.

3- How long does a standard radon test take?

A standard professional radon test takes a minimum of 48 hours, using continuous monitors placed in the lowest livable area of the home. During this peroid, windows and exterior doors must remain closed to ensure an accurate reading.