Radon on a Home Inspection Report — What Your Results Mean and What to Do

Should you even get a radon test?

If you haven't tested yet and you're deciding whether to add it: yes, in most cases it's worth it. Radon testing isn't included in a standard home inspection — it's a separate add-on, usually running $100 to $250. The test takes about 48 hours and measures the concentration of radon gas in the lowest livable level of the home.

Radon is the second-leading cause of lung cancer in the U.S., and you can't see, smell, or taste it. The only way to know whether a home has elevated levels is to test. Some regions have higher radon concentrations than others, but elevated readings can occur anywhere, regardless of geography.

If the home has a basement or slab foundation in contact with the ground, testing makes particular sense. If there's already a mitigation system installed, that's actually a good sign — it means a previous owner addressed the issue. You should still test to confirm the system is working.

What your radon number means

Radon is measured in picocuries per liter (pCi/L). The EPA has set an action level at 4 pCi/L.

Below 2 pCi/L. Low. No action needed. This is close to typical outdoor levels.

2 to 4 pCi/L. The EPA says consider mitigation at this range. It's not urgent, but long-term exposure at these levels still carries some risk. Many buyers proceed without mitigation at this level, though some choose to install a system for peace of mind.

4 to 8 pCi/L. Above the EPA action level. Mitigation is recommended. This range is common in areas with naturally high radon and is very fixable.

Above 8 pCi/L. Higher concentrations warrant prompt attention. Still fixable — mitigation systems typically reduce levels to below 2 pCi/L regardless of the starting point — but you'll want to make mitigation a condition of the purchase.

Above 20 pCi/L. Less common, but not unheard of. Even levels this high can be mitigated effectively. The higher the starting concentration, the more important it is to have a qualified radon professional design the system and verify results with a post-mitigation test.

The number itself is less important than whether you have a plan to address it.

How radon mitigation works

The most common approach is an active soil depressurization system. A pipe is routed from beneath the foundation slab or crawlspace to above the roofline, and a small fan creates negative pressure that pulls radon gas from under the home and vents it harmlessly outside.

The system runs continuously and uses about as much electricity as a light bulb. Once installed, it's low-maintenance — the fan motor may need replacement every 5 to 10 years.

For homes with crawlspaces, the approach may involve sealing the crawlspace with a vapor barrier and installing the venting system through it.

Post-installation, the home is retested to confirm levels are below 4 pCi/L. Most systems bring levels down to 1 to 2 pCi/L or lower.

Thinking about costs

Radon mitigation for a standard single-family home typically costs between $800 and $2,500, depending on the home's size, foundation type, and local labor rates. Most installations fall in the $1,000 to $1,500 range.

Crawlspace installations and homes with complex foundations may cost more. If the crawlspace also needs encapsulation or a vapor barrier, that's a separate cost — though addressing both at once makes sense if the crawlspace has moisture issues too.

These are rough ranges. A radon mitigation professional can give you a firm quote for your specific situation. The cost is modest compared to most other inspection-related repairs, and the system adds long-term value to the home.

More on thinking about repair costs.

Does radon affect your mortgage or insurance?

Radon doesn't typically block a mortgage or affect your homeowner's insurance. Unlike some electrical or structural findings, lenders and insurers generally don't require radon mitigation before closing.

The exception: some FHA and VA appraisers may flag radon in states where testing is standard practice, and some state-specific regulations require radon disclosure or testing. Check with your lender and your agent about local requirements.

Even when radon doesn't block closing, addressing it before or immediately after purchase is smart. It's a health issue worth resolving, and a mitigation system in place is a selling point when you eventually list the home.

Negotiating radon findings

Radon is a straightforward negotiation item because the scope is clear, the cost is predictable, and the fix is well-established.

Common approaches:

Ask the seller to install a mitigation system before closing, with a post-installation test confirming levels below 4 pCi/L. This is the cleanest outcome — you close knowing the issue is resolved.

Request a credit equal to the estimated mitigation cost. This gives you control over which contractor does the work, but means you'll handle the installation after closing.

Split the cost. In competitive markets or when the seller has leverage, a 50/50 split is a reasonable middle ground.

For most buyers, asking the seller to install the system is the stronger approach. The cost is low enough that most sellers will agree, and you avoid inheriting a to-do item. If the seller pushes back on handling it, a credit works too — the important thing is that the cost is accounted for.

More on repairs vs. credit.

When radon changes the deal

For the vast majority of home purchases, radon is a fixable finding — not a deal breaker. The system works, the cost is manageable, and the fix is permanent.

A few situations where radon might factor into a bigger decision:

The home has other significant issues (foundation problems, major water intrusion, expensive system replacements) and radon adds one more item to an already long list. In that case, the total picture matters more than radon alone.

The seller refuses to address or credit radon mitigation. This says something about how the rest of the negotiation may go.

The home has a history of multiple failed mitigation attempts. This is rare, but it would suggest an unusual foundation or soil condition that warrants more investigation.

On its own, a high radon reading is one of the most manageable findings on an inspection report. More on deal breakers.

If the home already has a mitigation system

Some homes already have a radon system installed from a previous sale or a prior owner's decision. This is a positive indicator — it means someone identified and addressed the issue.

Check the following: Is the fan running? (You should hear or feel a slight hum.) Is there a manometer or gauge on the pipe showing pressure? Was the system installed by a certified radon professional? When was the last post-mitigation test?

Even with a system in place, test the home during your inspection period. Systems can lose effectiveness if the fan fails, seals degrade, or the home's air dynamics change. A current test confirms the system is doing its job.

What to do next

If your radon test came back above 4 pCi/L, get a quote from a certified radon mitigation professional. Most state radon offices maintain lists of certified contractors. Ask the seller to install the system or provide a credit — this is a routine part of home sale negotiations and most sellers expect it.

If you're still deciding whether to test, add it to your inspection. The cost is small and the information is worth having, especially if you plan to use a basement or ground-level space as a living area.

For buyers sorting through radon alongside other findings — roof age, electrical concerns, moisture issues — InspectionTriage organizes your full report into a Decision Packet with every finding categorized, cost context included, and a negotiation framework ready to share with your agent.

See what's worth negotiating — free