A healthier basement starts with the air you can’t see
Along Colorado’s Front Range, winter can reveal what a basement is really doing: pulling soil gases through tiny foundation cracks, collecting moisture after snowmelt, and cycling temperatures that affect comfort. If you’re planning a basement remodel, radon testing before finishing a basement in Colorado is one of the smartest “do this first” steps—because once walls, ceilings, and flooring are installed, fixing air-quality issues can become more disruptive and expensive.
Why radon matters in Colorado basements
Radon is a naturally occurring radioactive gas that can enter a home from the soil beneath it. It’s odorless and invisible, which is why testing is essential. Colorado is a high-radon state—health agencies frequently emphasize that many Colorado homes test above recommended action thresholds.
The U.S. Environmental Protection Agency (EPA) recommends fixing a home when radon is at or above 4.0 pCi/L, and also encourages homeowners to consider mitigation when levels fall between 2.0 and 4.0 pCi/L because there’s no known “safe” radon level.
Why “test before finishing” is the safest sequence
A finished basement typically becomes a higher-use living space: bedrooms, family rooms, playrooms, gyms, theaters, and wet bars. That increased occupancy raises the importance of indoor air quality. Testing early lets you:
- Confirm baseline levels before construction changes airflow.
- Install mitigation cleanly (routing pipe/fan, sealing, electrical) before drywall.
- Coordinate with moisture control so your basement finishes stay durable.
A note on Colorado disclosures (buyers & sellers)
If you’re buying, selling, or planning around a remodel timeline, Colorado has specific radon-related requirements and disclosures tied to residential real estate transactions (including required contract language and related guidance). If you’re unsure what applies to your situation, it’s worth reviewing the official resources and confirming how it intersects with your renovation plans.
Radon, moisture, and comfort: how they overlap in a finished basement
Colorado basements can feel “dry,” but winter-to-spring transitions often expose weak points: condensation on cold foundation walls, damp corners after snowmelt, and musty odors from trapped humidity behind finishes. Moisture problems don’t cause radon, but basements that pull soil gases or have air leakage pathways often have the same entry routes that let moisture and odors creep in.
A smart plan treats the basement like a system: control bulk water, manage humidity, seal air leaks thoughtfully, and confirm radon levels before the remodel locks everything in place.
When to test, and what each test tells you
| Test type | Typical duration | Best used for | What to watch out for |
| Short-term radon test | 48–120 hours | Fast read before design, budgeting, and permits | Weather/ventilation changes can influence results; follow kit instructions closely |
| Long-term radon test | Usually 90+ days (varies by device) | Best picture of seasonal average exposure | Slower decision-making; may not fit a remodel timeline |
| Professional measurement | Varies | Added confidence, documentation, and guidance | Make sure the provider is properly credentialed/licensed where required |
Tip: If you need a fast decision before finishing, a short-term test is often the most practical first step. If it’s elevated, you can move forward with mitigation planning immediately.
Step-by-step: Radon testing before a Colorado basement remodel
1) Choose the right test for your timeline
If your remodel is starting soon, use a short-term test (commonly 48–120 hours). Colorado also offers guidance and access to test kits, including free or discounted options depending on availability.
2) Place the test in the lowest lived-in level
If your plan is to finish the basement and spend real time there, the basement is the level you should focus on. Follow the kit’s placement instructions carefully (room choice, height off the floor, and distance from drafts/HVAC returns).
3) Maintain “closed-house conditions” when required
Many short-term tests require you to keep windows closed (except normal entry/exit) for a set period before and during the test. This helps the test reflect typical worst-case indoor accumulation.
4) Interpret results using EPA guidance
Use 4.0 pCi/L as the key action point, and take 2.0–4.0 pCi/L seriously as a “consider fixing” zone—especially if your basement will become a bedroom, play space, or home office.
5) If elevated, plan mitigation before walls go up
The most remodel-friendly moment to route vent piping, plan fan placement, add electrical, and coordinate discreet soffits/chases is before drywall and trim. Colorado maintains resources to help homeowners find qualified radon professionals.
Colorado-specific finishing tip: build for winter comfort and spring moisture
If your basement feels cold in January and clammy in April, your remodel should prioritize comfort layers that don’t trap moisture where you can’t see it. That means paying attention to:
- Air sealing: Reduces drafts, odor pathways, and uncontrolled air movement from rim joists and penetrations.
- Insulation strategy: Done right, it improves comfort without creating a condensation trap behind finished walls.
- Humidity control: Helps protect drywall, flooring, and millwork—especially when snowmelt changes soil moisture.
When these building-science basics are coordinated with radon planning, you get a basement that’s not just beautiful—but comfortable and safer to live in.
Designing the basement you want—without hidden risks
Once radon and moisture are addressed, you can plan the fun parts with more confidence: a family room that’s warm underfoot, a home gym with resilient flooring, a theater room with sound control, a wet bar for entertaining, or a basement bathroom that makes the space truly livable.
ElkStone Basements focuses exclusively on basement remodeling and finishing—so the plan can be built around the realities of below-grade spaces from day one.
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Ready to finish your basement—starting with the right prep?
If you’re planning a basement remodel in Colorado and want a build plan that respects radon, moisture, and comfort from the start, talk with ElkStone Basements. We’ll help you map out next steps before finishes go in—so your new space is one you can feel good about using every day.
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FAQ: Radon testing and basement finishing in Colorado
The EPA recommends fixing the home if radon is 4.0 pCi/L or higher, and also suggests considering a fix between 2.0–4.0 pCi/L.
Yes. Radon can vary significantly from house to house due to soil conditions, foundation details, and airflow. The only reliable way to know your level is to test your home.
Many short-term tests take 48–120 hours.
In most cases, yes—after you plan for mitigation. The key is sequencing: address radon (and any moisture issues) before finishes go in so the solution is cleaner and less disruptive.
The Colorado Department of Public Health and Environment (CDPHE) provides radon education, testing guidance, and options for obtaining test kits, plus information on finding radon professionals.
Glossary
Radon (Rn): A naturally occurring radioactive gas that can enter homes through the ground and accumulate indoors.
pCi/L: “Picocuries per liter,” a standard unit used in the U.S. to report radon concentration in air.
EPA action level: The EPA’s recommended threshold for taking corrective action: 4.0 pCi/L.
Mitigation: A set of methods used to reduce indoor radon levels, commonly by venting soil gases from beneath the foundation to the outside.
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