Why Kansas City Homes Get Radon

I test and mitigate radon all over the metro, and the question I hear most is some version of "why would my house have radon?" It is a fair question. Radon is invisible and has no smell, so nothing about your home tips you off. The short answer is that Kansas City sits on the kind of ground that produces it, and our houses are built in a way that pulls it inside. Here is what is actually going on under your feet.

We sit in EPA Radon Zone 1

The EPA splits the country into three radon zones. Zone 1 is the highest, where the predicted average indoor level is at or above the 4 pCi/L action level. Most of the Kansas City metro, on both the Missouri and Kansas sides, falls in Zone 1. That does not mean every house is high, but it means the ground here is capable of producing enough radon to be a problem, and a meaningful share of homes test above the action level. It is common enough that I find elevated readings in newer builds and older homes alike.

It starts in the soil and bedrock

Radon comes from the natural breakdown of uranium in soil and rock. Our region has limestone and shale bedrock and clay-heavy soils, and as the uranium in that ground decays it releases radium, which decays into radon gas. That gas moves up through the pore spaces and cracks in the soil until it reaches the surface. Out in the open it just disperses into the air and is harmless. The trouble starts when the path to the surface runs through the bottom of your house instead.

Your house actually pulls it in

A home does not just sit passively over the soil, it draws air out of it. Warm air rises and escapes through the upper floors, which creates a slight vacuum lower down. That is the stack effect, and it is strongest in our cold winters when the furnace is running. The low pressure at the foundation pulls soil gas, radon included, in through cracks in the slab, gaps around plumbing penetrations, sump pits, and the seams where the floor meets the wall. Your house is essentially breathing in from the ground beneath it.

Newer and tighter homes are not safe from it

People assume a new home is fine and an old one is the risk. Radon does not work that way. A tightly sealed, energy-efficient home holds the gas in once it gets inside because there is less natural air exchange to dilute it. I have measured high levels in houses just a few years old. Finishing a basement into living space also matters, because you are now spending hours in the lowest part of the home where radon concentrates.

The only way to know is to test

Because you cannot see or smell radon, geography and house age only tell you the odds, not your actual number. The only way to know your level is to measure it, and a short test is inexpensive and simple. If it comes back elevated, a mitigation system vents the gas from under the slab to above the roofline before it can enter. You can read how that works on our radon mitigation system page, and start with a radon test.

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