Several years after finishing the basement, you might find that the radon level has increased above the EPA’s action limit (4 pCi/L) and must be reduced to make the house marketable.

Does finishing basement lower radon?

Again, the only way to ensure you are removing radon from your home is with a mitigation system. Sealing the basement floor can help, but just sealing the cracks is unlikely to reduce your radon levels in the long term. Sealing all cracks and applying non-porous, thick epoxy coatings would be a better step.

How do I know if my basement has radon gas?

The only way to know if your house contains indoor radon is to test for it. The tests are simple and inexpensive. You can buy a home kit or have a professional do it for you. The amount of radon in the air is measured in “picocuries per liter of air,” or “pCi/L.”