Dry Basement Network connects homeowners with waterproofing contractors. Radon testing and mitigation are separate specialties; this guide explains how the two relate so you can ask the right questions.
What radon is and why it matters
Radon is a colorless, odorless radioactive gas that forms naturally in soil and rock and can enter homes through the foundation. According to the National Cancer Institute, it is the second leading cause of lung cancer in the United States, linked to an estimated 15,000 to 22,000 lung cancer deaths a year. The U.S. EPA estimates that about 1 in 15 homes has elevated radon levels.
The EPA’s action level is 4 picocuries per liter (pCi/L); it also recommends considering a fix between 2 and 4 pCi/L, since there is no known safe level. The only way to know your level is to test.
How radon and basement water are connected
- Same entry points. Cracks, the joint between wall and floor, pipe openings and open sump pits let in both water and soil gas.
- Open sump pits are a direct path from the soil into the basement. Newer editions of the International Residential Code require a gas-tight, removable cover on sump pits, as the DOE’s Building America Solution Center notes.
- Drain tile and gravel under or around the slab are exactly where radon systems draw soil gas from. The EPA’s technical guidance on active soil depressurization describes using existing drain tile and sump pits as suction points.
Does waterproofing fix radon?
Not by itself. Sealing cracks and covering the sump pit reduce entry points and help a radon system work better, but EPA guidance treats sealing as a supporting measure, not a reliable stand-alone fix. The proven method is active soil depressurization: a fan and pipe create lower pressure under the slab, so soil gas is drawn out and vented above the roof instead of entering the house.
Does waterproofing make radon worse?
It shouldn’t, if it is done well. An interior drainage system with a sealed, gasketed sump lid and sealed wall membranes generally reduces open pathways. An open or loosely covered pit after a waterproofing job is the thing to avoid. If you test before and after major basement work, you will know.
Planning both together
- Test first. Short-term test kits are inexpensive; follow the instructions and test in the lowest lived-in level.
- If radon is high and you also need waterproofing, tell both contractors. A sealed sump and an interior drain can be designed so that a radon system can later draw from the drain tile.
- Use certified radon professionals. Pennsylvania requires anyone other than the owner who tests for or mitigates radon to be certified by the Department of Environmental Protection, and New Jersey requires radon testing and mitigation businesses and professionals to be DEP-certified. Other states have their own rules or rely on national certification.
- Retest after any mitigation and after major basement work.
Related
See sump pump installation (sealed lids), finishing a basement and musty basement smells.
Sources
- National Cancer Institute: Radon and cancer fact sheet
- U.S. EPA news release: about 1 in 15 homes has elevated radon
- CDC/ATSDR: Standards and regulations for radon (EPA action level 4 pCi/L)
- PNNL Building America Solution Center: Sump pump cover gasket (IRC gas-tight cover)
- U.S. EPA: Radon reduction techniques for existing detached houses (active soil depressurization)
- Pennsylvania DEP: Radon certification
- New Jersey DEP: Radon information