How To Seal A Basement For Radon [Inc. Floor Cracks]

Disclosure: We may get commissions for purchases made through links in this post.

Exposure to low radon levels is nothing to be surprised about, mainly because it comes from several natural sources. But when you have an unfinished foundation, radon can seep through cracks and increase indoors. Should you seal it, and how should you do it? We've done research and put together a guide to help you.

To seal the basement floor and walls, here are the steps:

  • Clean up the area.
  • Check for cracks and openings.
  • Inspect basement surroundings.
  • Apply the sealant.

Other ways to keep radon out include filling up cracks and gaps, covering exposed dirt or concrete, and increasing airflow around the basement.

You can protect yourself from potential health complications by lowering radon levels in your home. Keep reading to learn more about other methods to reduce radon in the basement and what materials you can use.

Classic rustic inspired basement with white flooring, wooden cabinets and white tile flooring, How To Seal A Basement For Radon [Inc. Floor Cracks]

Does Sealing My Basement Lower Radon Levels?

It's still unclear whether radon lowers after sealing an unfinished basement. Since the process involves repairing foundation cracks and leaks, it's safe to say that it helps reduce radon, but it cannot completely eliminate it.

Cream painted living room

Most professionals recommend installing radon mitigation systems for homeowners who are unsure of their exposure levels. But even this requires sealing the basement.

Regardless of its efficiency, a sealed basement offers several benefits besides radon prevention, such as waterproofing, increased value and protection, and lower energy costs.

Why You Should Avoid Radon

Next to cigarette smoking, radon is one of the leading causes of lung cancer, which poses a higher risk because the exposure comes from your natural surroundings.

Radon forms when radioactive materials break down into rocks, soil, and groundwater, which are materials you may commonly find around or under your home. People are constantly exposed to it but at low, harmless levels.

To ensure radon levels remain safe in your environment, consider testing for it using a radon test kit. You can also contact a professional radon contractor for more accurate results.

Get this radon gas test kit on Amazon.

How To Seal A Basement

As the base of your home, it's crucial to have a sturdy, durable foundation. But no matter how strong it may be, it will eventually grow cracks as time passes.

Fortunately, you can do many basement sealing techniques by yourself, with only a few tools to start. These include caulk or putty, floor or wall sealant, brush or roller, dish soap, and a scrub brush.

Here is how to get started:

1. Clean Up The Area

Most sealants work best when you apply them to the damaged surface, so you may need to do a little cleaning before moving forward.

Mix dish soap with warm water and then use a scrub brush to remove debris from surfaces.

For mold or mildew, use a mold removal cleaner, bleach solution, or baking soda mixture to soak it in before scrubbing. Rinse it off with warm water and wait for it to fully dry.

If the surface has existing paint or efflorescence, remove them as well. You can use a paint stripper or scrape it off with a putty knife.

2. Check For Cracks And Openings

Locate the surface for cracks or gaps on or around it. Repairing them will waterproof your foundation and prevent potential leaking.

To do this, use hydraulic cement, caulk, or putty to fill the openings, then wait for it to harden and dry. Most experts recommend using a variant that is waterproof and elastic or flexible.

3. Inspect Basement Surroundings

As much as possible, identify the water sources inside and outside the basement. When inspecting the exterior, relocate plants that require watering and repair broken gutters and downspouts.

If needed, you can adjust them to ensure the water that passes gets released away from your home.

4. Apply The Sealant

Worker applying waterproofing sealant on the concrete

After patching the foundation and removing water sources, apply a coat or two of your chosen sealant onto the surface with a roller or brush.

Read through the sealant's provided instructions to make sure you didn't miss out on any additional preparation.

Read this post for a more in-depth guide on sealing foundation indoors: Can You Seal Foundation From Inside? 

Steps To Seal Floor Cracks

Worker putting adhesive on the floor for placing tiles

Unlike basement walls, the floor is often in closer contact with materials that make up radon. So the gas goes through these gaps to enter a home. Once fixed, there won't be room for radon to make a way inside.

Below are steps to seal floor cracks for concrete and wooden floors.

 On Concrete Floors

For your tools, you will need a wire or scrub brush, concrete cleaner or dish soap, vacuum, a masonry chisel, hammer, trowel, brush, bonding adhesive, and concrete filler (sand mix, caulk, etc.).

  1. Thoroughly clean the area by scrubbing debris with the scrub brush and cleaner. Use the wire brush to clean the crack, then sweep or vacuum any remains.
  2. After cleaning and drying, partially widen and undercut the edges of the crack using the chisel and hammer to ensure the patch stays in place later. Wear proper eye protection when chiseling.
  3. Use a paintbrush to coat the surface of the crack with a layer of bonding adhesive and wait for it to dry. It usually takes an hour, but you can tell it's dry once the color becomes transparent. Some bonds require mixing instead of brushing, so check the manufacturer's instructions before anything else.
  4. Prepare your filler. Follow the instructions provided with either material you will use. For sand mixes, make sure it's pliable but not runny.
  5. Fill the crack as much as you can using a trowel. If you're using caulk, you can use the tube it comes with to pour into the gap. Scrape off and smoothen excess filler with the trowel. Leave it for about a day to completely dry.
  6. Seal the concrete using a basement floor sealer to waterproof it in the future. Two coats are usually enough to protect it, but consider applying an extra coat in high-traffic spaces.

On Wooden Floors

Modern basement interior with white painted walls and wooden laminated flooring

When repairing cracks on wooden floors, you need a broom, wet rag, vacuum, wood filler or epoxy putty, putty knife, wood chips or sawdust, sandpaper, and wood stain.

  1. Determine if the crack needs replacing or sealing. Some damages may even require more if the problem is not cosmetic.
  2. Clean up the surface using a broom. For stubborn dirt, use a wet rag or brush and floor cleaner. Finish up by vacuuming the floor before leaving it to dry.
  3. Prepare the filler according to the instructions, then apply it to the crack with a putty knife.
  4. Add fine wood chips or sawdust if there's too much space to fill. Flatten it until level using the putty knife.
  5. Once the filler dries, sand it down until smooth.
  6. Apply wood stain the same color as the existing floor, then wait for it to dry.

What Can I Do To Reduce Radon?

Radon comes directly from homes, making it almost unavoidable. Although you cannot eliminate it through home remedies, you can reduce it by preventing it from entering the home or giving it the means to go out.

Here are a couple more ways for you to reduce radon effectively.

Install Ceiling Fans

A ceiling fan inside the basement

Ceiling fans are more likely to increase airflow while reducing radon levels since it only circulates and reuses the surrounding air.

Exhaust fans tend to increase radon because there would be more air pressure inside, so most wouldn't recommend using them.

If your home has dangerous radon levels, consider purchasing a radon mitigation fan instead of a regular ceiling fan.

Get this radon mitigation fan on Amazon.

Open Windows

Awning window in the basement

Having sufficient ventilation in a basement is good, so radon doesn't get trapped inside. If your basement has windows, keep them open whenever possible and as close to the soil as possible.

Radon diffuses into the air when it has better access to the outside, allowing you to reduce radon while getting fresh air and increasing airflow.

Read this post for more ways to ventilate a basement without windows: How To Ventilate A Basement With No Windows.

Cover Exposed Ground

Any exposed soil or concrete can release more radon if there's no way to slow or stop it. This issue is common in unfinished basements due to the exposed ground.

You can reduce levels by covering these portions with high-density polyethylene plastic or sealing along the edges.

Get these polyethylene sheets on Amazon.

Radon Paint Sealer Vs. Radon Mitigation System

Carpeted basement flooring with white painted walls

Experts suggest installing a proper radon mitigation system if you're dealing with dangerous radon levels. If radon readings are low, radon paint sealer is enough to prevent it from increasing.

Sealing a basement is also more affordable than radon mitigation systems. However, having these in addition to other radon-reducing tricks is best.

If you don't have a choice, you can install a mitigation system or have radon gas removed. You can expect to pay $450 and as high as $3,000.

In Closing

Classic rustic inspired basement with white flooring, wooden cabinets and white tile flooring

Sealing your basement helps prevent radon from spreading further throughout your home. Primarily, it works because it requires patching holes and cracks where radon may come through.

Fixing gaps and leaks in the basement foundation can be done for walls and flooring using concrete or wooden fillers, then finishing up with a sealant.

Leave a Reply