Does Basement Waterproofing Affect Radon Levels in Homes?
Basement waterproofing can change radon levels because the same openings that let water in, such as an open sump pit, gaps along drain tile, and cracks in the floor, can also let soil gas in. The Pennsylvania Department of Environmental Protection (DEP) says approximately 40% of homes tested in Pennsylvania have radon above the EPA action guideline of 4 picocuries per liter (pCi/L), so any work on a below-grade floor or pit deserves a radon test before and after. Radon and sump pump pits are linked in a simple way: an uncovered pit is a direct opening to the soil under your slab.
Pennsylvania also draws a legal line many homeowners never hear about. A DEP certification guide explains that the Radon Certification Act of 1987 requires DEP certification before any person conducts radon testing, radon mitigation, or radon laboratory analysis in the state, and it defines mitigation as repairing or altering a building to reduce indoor radon. This post covers how waterproofing work can open or close soil gas entry points, what a sealed sump lid does and does not do, why a drainage system is not a radon system, and how to test around a waterproofing project.
How does radon get into a basement?
Radon is a radioactive gas that forms in soil and rock and moves into a house through any opening in the foundation that touches the ground. PA DEP describes it as "an odorless, invisible, radioactive gas that can enter your home from the ground through cracks in the foundation."
EPA's A Citizen's Guide to Radon lists the common entry points:
Cracks in solid floors
Construction joints
Cracks in walls
Gaps around service pipes
Cavities inside walls
The water supply
Several of those are also places a basement leaks, which is why waterproofing and radon belong in the same conversation. If floor cracks are your main water problem, our post on stopping water that comes up through floor cracks explains the repair side.
Radon shows up in every kind of house. EPA's guide says it "can be a problem in homes of all types: old homes, new homes, drafty homes, insulated homes, homes with basements, homes without basements."
What is the link between radon and sump pump pits?
A sump pit is a hole in your basement floor that collects water from the soil and from any drain tile around the foundation. By design, it connects the inside of your basement to the ground under the slab. When the lid is missing, loose or has open holes for the pipe and cord, soil gas can move up through the pit as easily as water moves into it.
That is why sealed, airtight sump lids come up so often. EPA's Indoor airPLUS construction specifications for new homes include the line "Air seal all sump covers." EPA's Consumer's Guide to Radon Reduction adds that when a home has a sump pump, "the sump can be capped so that it can continue to drain water and serve as the location for a radon suction pipe."
A sealed lid still lets the pit drain while the cover blocks air. Capping the pit and pulling air from it are separate steps, and only the second one is a radon reduction system.
If you are deciding whether your home needs a pit at all, read whether your basement needs a sump pit.
What about a radon sump pit cover?
A radon sump pit cover is simply a gasketed, sealed lid made to keep air from passing through the pit opening, often with a clear port so you can see the pump. On its own, it does not lower radon to a known level, and only a test tells you where your levels stand.
Can waterproofing work raise or lower radon?
It can do either, and you will not know which without a test.
Work that tends to close entry points:
Sealing a previously open sump pit with an airtight lid
Repairing cracks in the floor or walls
Sealing gaps where pipes pass through the slab
Work that can open new paths, at least for a while:
Cutting the slab to install interior drain tile
Breaking out a section of floor to set a new sump basin
Leaving a pit uncovered during or after the job
EPA's Citizen's Guide puts it plainly: "Because major renovations can change the level of radon in any home, always test again after work is completed." The same guide says that if you plan a major structural renovation, "such as converting an unfinished basement area into living space, it is especially important to test the area for radon before you begin." For a closer look at what interior waterproofing involves, see how basements are waterproofed from the inside.
Is a waterproofing system the same as radon mitigation?
No. A waterproofing system manages water, and a radon mitigation system manages soil gas. They can share parts of the same basement, but they are built and tested for different jobs.
EPA's Consumer's Guide says sealing cracks and openings "is a basic part of most approaches to radon reduction," but it also says "EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently." In other words, the sealed lid and patched cracks that come with good waterproofing help, but they are not a fix you can count on.
The same guide notes that some homes have drain tiles or perforated pipe to move water away from the foundation, and that "suction on these tiles or pipes is often effective in reducing radon levels." Pulling suction on that pipe is radon mitigation, and in Pennsylvania that work falls under DEP certification.
A Better Choice, Inc. does not perform radon testing or radon mitigation. If your test comes back high, DEP keeps a directory of state-certified radon contractors, labs and testers on its website, and the DEP Radon Hotline at 800-237-2366 also provides certified contractor lists.
How should you test for radon before and after waterproofing?
PA DEP says home test kits cost about $20 to $30 at hardware stores and are sent to Pennsylvania-certified laboratories for analysis.
A simple order of operations:
Test before the work starts. PA DEP recommends testing the lowest floor, and says basements often have higher levels.
Keep the result so you have a baseline.
After the waterproofing is finished and the sump lid is sealed, test again in the same spot.
If either result is 4 pCi/L or higher, EPA's guidance is to fix the home when the level is confirmed at that point. DEP suggests a confirmation test when an initial result is above 4 pCi/L.
Timing matters. DEP says winter months are the best time to test, since homes are closed up and radon concentration is highest. In Greensburg, Irwin or anywhere in Westmoreland County, a heating season test gives you the more conservative number.
If you already have a radon system and are adding waterproofing, loop in the certified mitigator before any work touches the pit or drain tile. EPA's Consumer's Guide says a post-mitigation test should be done "within 30 days of system installation, but no sooner than 24 hours after your system is in operation with the fan on," and DEP says homes with a system should retest about once every two years.
Does humidity or air movement in the basement matter for radon?
Air moves between floors, and our post on the stack effect in home ventilation explains how. The basement is not a sealed box, so whatever enters at slab level can travel.
Moisture control and radon control are still separate goals. A dehumidifier or ventilation system can help a damp basement feel and smell better, but it is not a radon reduction system, and nobody should sell it as one. Test for radon on its own schedule, no matter what equipment is running.
FAQ
Can radon come through a sump pump pit?
Yes. An open or loosely covered sump pit connects the basement to the soil under the slab, so soil gas can move through it. An airtight lid closes that opening, and a radon test tells you whether levels are acceptable.
Should I avoid buying a house with a sump pump?
A sump pump by itself is not a reason to walk away. Ask for a recent radon test result, check that the pit has a sealed cover, and consider your own test after closing.
Does radon in the basement go upstairs?
It can. Air moves between floors, so gas that enters at the basement level can reach living spaces. EPA's Citizen's Guide says test kits belong in the lowest lived-in level of the home, which is the basement if you use it often and the first floor if you do not.
Will sealing my sump lid fix a radon problem?
It helps close one entry point, but EPA does not recommend sealing alone to reduce radon because it has not been shown to lower levels significantly or consistently. A confirmed high result calls for a certified radon mitigator.
Who can install a radon system in Pennsylvania?
Only people and firms certified by PA DEP. The Radon Certification Act of 1987 requires certification for radon testing, mitigation, and lab analysis, and DEP lists certified providers in its online directory.
How much does a radon test cost in Pennsylvania?
PA DEP says do-it-yourself test kits generally cost $20 to $30.
Should I test before finishing my basement?
Yes. EPA says testing before converting an unfinished basement into living space is especially important, and it recommends testing again after major renovation work is done.
Waterproofing Help From A Better Choice, Inc.
A Better Choice, Inc. has served the Greater Pittsburgh area since 1996, working from North Huntingdon and serving Westmoreland, Allegheny, Butler and neighboring counties. Our basement waterproofing page walks through the wet basement warning signs we look for, and our home ventilation systems page covers the EZ Breathe and Humidex systems we install. We do not do radon testing or mitigation, so we recommend you test before and after any waterproofing project and call a DEP-certified radon professional if your numbers are high. To have your basement looked at, schedule a free inspection.
Visit A Better Choice, Inc. or call 1-800-343-2357 today. Contact us for more information.
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