Why Some Homes Have Higher Radon Than Their Neighbors

One of the most confusing things about radon is how inconsistent it can be. A homeowner tests and finds elevated radon. The neighbor tests and gets a low result. Same street. Same year built. Same weather. Completely different numbers.

This happens all the time, and it often leads people to doubt the test instead of understanding the science behind it.

The reality is that radon behaves very locally. It is influenced by conditions beneath and within a single structure, not by what is happening next door.

What Is Happening Underground

Radon comes from uranium in soil and rock, but that soil is not uniform even across short distances. Small changes underground can dramatically affect how radon moves.

One home may sit over more permeable soil that allows gas to flow easily. Another may sit over compacted clay that redirects radon elsewhere. Fractures in rock, old root paths, and disturbed soil from construction can all create radon pathways that stop abruptly a few feet away.

Radon does not spread evenly like a smell. It follows the path of least resistance.

Foundation Design Matters More Than You Think

Even when homes look identical from the outside, their foundations often behave differently. Minor differences during construction can affect radon entry.

Things that can vary between neighboring homes include slab thickness, sealing quality, expansion joints, sump pits, and how utility lines were routed. These small differences can create or block radon entry points.

A single unsealed penetration can be enough to change radon behavior significantly.

Pressure and Airflow Are Personal to Each House

Homes create their own pressure environments. HVAC systems, exhaust fans, fireplaces, and even how often doors are opened influence indoor pressure.

If one home consistently pulls more air from the soil beneath it, it will pull more radon inside. That effect has nothing to do with what the neighbor is doing.

This is why radon testing cannot be shared or assumed. Each home must be evaluated individually.

Why Comparing Results Is Misleading

When people hear that a neighbor tested low, they assume that means they are safe. Unfortunately, radon does not work that way.

A neighbor’s test tells you almost nothing about your own exposure. It may provide reassurance, but it does not provide data.

This is why testing agencies consistently say the same thing. Test the home, not the neighborhood.

At home screening tools like the Detekt Home radon test are designed specifically to capture what is happening inside a single living space, regardless of nearby results.

The Takeaway

Radon differences between neighboring homes are normal, not suspicious. Soil conditions, foundation details, and airflow patterns are unique to each structure. The only reliable way to know your radon risk is to test your home, not compare it to someone else’s.

By Chris M., PhD