Home on Concrete Slab: What's the Radon Risk?

LESLIE: J.C. in North Carolina is on the line with a question about radon. How can we help you?

J.C.: If your home is built on a concrete slab, then are you in danger of radon effect?

TOM: Well, you could potentially be in danger of it but the risk, that would be a far smaller chance of you having an elevated radon level on a concrete slab than if you had a basement. Because radon is a gas that emits from the soil and typically, it gets into the home at the basement level through concrete-block walls and the concrete floor and the gaps around it, builds up in the basement. And it’s typically highest in the basement, then it gets far less on the first floor, second floor and so on.

J.C.: Yes. And I would assume it would be more dangerous with a crawlspace then.

TOM: Actually, I think it’s less dangerous with a crawlspace and here’s why: because crawlspaces are open to the outside all the time, so they’re completely ventilated. So the highest risk would be if A) you were in an area that was prone to radon and B) you had a basement. Then you would definitely want a test.

Now, in North Carolina, there are three different Radon Zone levels: 1, 2 and 3. Very little of the state is in the Radon Zone 1, which is the highest risk. I’d say about 30 percent, maybe 25 percent is in Radon Zone 2 but the rest of the state is all Radon Zone 3, which is the lowest risk.

And in your area, which is Lee County, you’re in Radon Zone 3. So you’re in an area that has a low risk of radon, you’re on a concrete slab. I’d say the likeliness of you having a radon problem is very small but the only way to know is to test, J.C. And you can do that with a charcoal absorption canister very inexpensively.