A properly finished basement is a valuable addition to any home. However, multi-level homes often face issues with high radon levels and moisture control in basements. when it comes to the do’s and don’ts of finishing a basement, its important to pay attention to flooring, drainage, and radon.
Here’s a comprehensive guide on what you need to know about radon in basements and how to finish this space to ensure its safety and longevity.
How Common is Radon in Basements?
Radon is a naturally occurring radioactive gas that can enter homes through cracks and openings in the foundation. Basements, being below ground level, are particularly susceptible to radon infiltration.
In fact, the EPA estimates that nearly 1 in 15 homes in the U.S. have elevated radon levels, and basements are often the most affected areas. And in some areas in the U.S., over 50% of homes have elevated radon levels. This makes radon testing for basements imperative to determine the next steps before continuing a renovation.
What Causes High Levels of Radon in Basements?
Radon in homes can be influenced by several factors. Understanding them can help homeowners take proactive measures to reduce radon exposure in an unfinished basement or in a home without a basement.
- Soil Composition: Radon is produced by the decay of uranium in the soil, which varies by region.
- Foundation Type: Depending on whether gravel is underneath your foundation or just a slab, the radon levels of your home can be affected.
- Foundation Cracks: Even minor cracks in the foundation can allow radon to seep into your basement.
- Air Pressure Differences: Lower pressure inside your home compared to the surrounding soil can draw radon gas indoors.
Additional Contributing Factors For Radon in Homes
Water Supply
Homes that use well water can have higher radon levels, as radon can dissolve and accumulate in groundwater. When this water is used for drinking, cooking, or bathing, radon can be released into the air.
Testing your water supply for radon, especially if you have a private well, is essential in comprehensive radon mitigation.
Building Materials
Seasonal Variations
Radon levels can fluctuate with the seasons. During winter, homes are usually sealed to conserve heat, reducing ventilation and potentially increasing radon levels. Conversely, in the summer, windows and doors may be open more frequently, increasing ventilation and lowering indoor radon levels.
Regular testing during different seasons can provide a more accurate picture of your home’s radon levels throughout the year.
How To Determine if There's Radon in My Basement
Testing is the only way to know if you have high radon levels in your basement. You can purchase a radon test kit or hire a professional radon testing service. Regular radon testing for your basement is recommended, especially if you haven’t tested in several years or if you’ve made significant changes to your home.
How to Reduce Radon in an Unfinished Basement (or Finished)
If you test your home for radon and the levels come back higher than the recommended 4.0 pCi/L or lower, you’ll need radon mitigation for your basement. Reducing radon levels in a basement typically involves installing a radon mitigation system.
Here are some effective methods:
- Sub-Slab Depressurization System (SSDS): This system involves venting radon from beneath the foundation before it can enter the home.
- Sealing Cracks: Seal all cracks and openings in the foundation and basement walls to reduce radon entry.
- Ventilation: Increase ventilation in the basement to help dilute and disperse radon gas.
Can You Prevent High Radon Levels in a Basement?
While completely preventing radon from entering your home is challenging due to its natural occurrence, there are effective steps you can take to minimize its entry and ensure a safer living environment.
- Proper Construction: Ensure new homes are built with radon-resistant features.
- Regular Maintenance: Keep your basement well-maintained and promptly address foundation cracks or openings.
- Testing and Mitigation: Regularly test for radon and install a mitigation system if levels are high.
The Dos And Don’ts For Properly Finishing A Basement
A basement should be built like a boat to keep water out. But most houses are built on porous walls and floors with nothing between the wet and the dry. In a home built like a sieve, if you want finish materials in the basement, you must first manage the moisture in the walls and floor.
Here’s a list of dos and don’ts that show everything you need to know about finishing a basement.
Drainage:
- DO install a drain-tile system with a sump pump that discharges any water within a minimum of 5 feet from the foundation.
- DO extend the interior drainboard from the drain tile to at least 6 inches above grade. The best sheathing is dimpled.
- Don’t allow water discharge to pool near the foundation, as this can lead to increased moisture and potential radon entry.
- Don’t ignore regular maintenance of the sump pump and drain-tile system; ensure they function correctly to prevent water accumulation.
- Don’t use non-dimpled sheathing, as it may not provide adequate drainage and moisture control.
Walls
- DO frame with steel studs set on a capillary break, such as a sill seal (this also helps with uneven floors).
- DO hold framing 1 inch away from the foundation walls—no exceptions!
- DO spray high-density polyurethane foam 2 to 3 inches thick behind the stud wall and all the way up onto the rim joist. If you choose to use batt insulation, don’t let it touch the foundation walls.
- DO install paperless drywall and hold it ½ inch off the floor.
- DON’T let the wall framing touch the walls or the floor (treated lumber wicks water).
Floors
- DO install an active Sub-Slab Depressurization System (SSDS) to control moisture and radon. The SSDS can remove up to 10 gallons of water a day from under your home, helping to improve air quality and reduce the potential for mold and musty odors. As a side benefit, it will also reduce radon levels in your home!
- DO use moisture-resistant flooring, such as ceramic tile or vinyl composition tile. If you want the look of wood, cover the slab with a vapor-control layer with taped seams and install a glued or dry-fit engineered click-lock floating floor system.
- DON’T install carpet.
Radon
- DO test your home every two years whether your basement is finished or unfinished.
- DO have a professionally installed mitigation system if your radon levels are 4.0 pCi/L or above.
- DON’T neglect to have your radon mitigation system maintenance by a radon professional.
Contact Us for Radon Testing and Mitigation
Ensuring your basement is safe from radon is our top priority.
If you’re concerned about radon in your basement, contact us today to schedule a radon test. Our team of experts can also install the best radon mitigation system tailored to your home’s needs.
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