The inspection report lands on day seven of your ten-day objection period. You and your agent go through it line by line: the roof has some granulation loss, the water heater is nearing the end of its service life, the crawl space could use a vapor barrier. You negotiate, you agree, you move toward closing.
Then, three days later, the radon result shows up. It was never part of the negotiation because it wasn't back yet. The canister sat in the lowest room of the house for the better part of a week, then rode to a lab in a stamped envelope, and now you're looking at a number that either changes nothing or reopens a conversation you thought was closed.
This is the part of a Durango closing that catches people off guard, not because radon is exotic, but because the timeline works against it. Everything else on the inspection is visible and fast. Radon is invisible and slow. And in La Plata County, the odds that it matters are close to a coin flip.
The Zone Label Undersells What's Actually Under the House
If you search around for La Plata County's radon risk, you'll find a genuine disagreement in how sources describe it. Some mitigation companies cite the county's official EPA Radon Zone 2 designation, which predicts an average indoor screening level between 2 and 4 pCi/L, technically within the range the EPA considers acceptable. At least one local inspector describes the county as EPA Zone 1, the agency's highest risk category. Even the professionals can't agree on which map applies here.
The zone label matters less than what happens when you set the map aside and look at the actual test results. The Durango Herald reported in January 2026 that homes in La Plata County have roughly a 50-50 chance of testing above the EPA's action level of 4.0 pCi/L, with an average reading around 5.5 pCi/L. A separate Herald analysis of 875 homes tested over 12 years put the county average at 5.75 pCi/L, with a recorded high of 325 pCi/L. For comparison, the national average sits around 1.3 pCi/L.
That's the number worth sitting with: the average home here doesn't hover near the action level, it exceeds it. A "moderate" zone rating implies most homes are fine and a few outliers pull the average up. The actual data says the opposite. The typical result already crosses the line where the EPA recommends mitigation.
The Geology Doesn't Care What Your House Looks Like
Radon comes from the natural breakdown of uranium in soil and rock, and Southwest Colorado's geology produces it at higher rates than most of the country. That means the risk isn't tied to how old a house is, what it's built from, or what neighborhood it sits in. A downtown Victorian and a new build up-valley can post wildly different results, and two homes next door to each other can too, because what determines the reading is the specific ground beneath that specific foundation, not the block it's on.
This is worth knowing before you assume a newer home is automatically safer. It might be easier to fix if it isn't, but the presence of radon itself has nothing to do with construction date.
New Construction Has a Head Start Resale Homes Don't
Here's where the transaction math actually diverges. Both the City of Durango and La Plata County require new homes to be built with the ability to add a radon mitigation system, even though neither requires a full active system be installed before the certificate of occupancy is issued.
Butch Knowlton, director of La Plata County's Building Department, explained the logic in a Durango Herald interview: the county didn't want to force a complete installation on every new house because it would waste money on homes that never test high. Instead, builders install the rough plumbing, the vent stack, the capped location, so that if a future owner tests high, a contractor can add the fan and finish the system without cutting into a finished slab.
That distinction changes what a radon problem costs to fix depending on which side of the construction line your home falls on:
| New construction with rough-in | Resale without existing rough-in | |
|---|---|---|
| Test cost | $150 to $250, often bundled into inspection | $150 to $250, often bundled into inspection |
| Mitigation if elevated | Fan installation onto existing vent stack, typically at the lower end of the range | Full sub-slab depressurization system cut through the foundation |
| Typical mitigation cost | Often near $800 to $1,000 | Often $1,000 to $1,500, more with a complex foundation or crawl space |
The gap isn't enormous, but it's real, and it's exactly the kind of detail a buyer should ask about before waiving further inspection contingencies on an older resale property.
Who's Actually Allowed to Hand You That Result
One more piece of friction that shows up more often than buyers expect: as of July 1, 2022, Colorado requires all radon testing and mitigation to be performed by a state-licensed radon professional, with one narrow exception. Homeowners can test or fix radon themselves in a home they own and occupy. That exception does not extend to a seller's contractor testing a spec home, a landlord testing a rental, or anyone testing on behalf of someone else's transaction.
Practically, this means the radon result attached to your inspection report should come from someone carrying an actual state license, not a general handyman doing you a favor. If a seller hands you an old test result from a few years back, it's worth confirming who performed it and whether conditions in the home have changed since.
Building Your Timeline Around the Test, Not Around Hope
Because a short-term radon test needs three to seven days in the home before it goes to a lab, and lab turnaround typically adds another week to ten days, the math rarely favors waiting. If your objection period is ten business days, a radon test started on day one might not return a result until after everything else has already been negotiated and signed off.
Winter is technically the ideal testing season, since a closed-up house with the windows shut gives a more accurate reading. Most Durango transactions don't get to pick their season, and a test run during a mild stretch with windows occasionally open can undercount actual exposure. A licensed professional will typically note testing conditions on the report, which is worth asking to see rather than just the final number.
The practical fix is simple: start the radon test the same day your inspection period opens, not after you've read through the rest of the report. That way, if the result comes back elevated, you still have room to negotiate it alongside everything else, instead of reopening a closed conversation days before closing.
A Few Questions Worth Settling Early
If my Durango home's radon test comes back high, does the deal fall apart? Not usually. A high result is a negotiation point, not a dealbreaker. Since most La Plata County homes test somewhere in this range, sellers and their agents are generally familiar with the request to split or cover mitigation costs, particularly on resale homes without an existing rough-in.
Does buying new construction mean I can skip the test? No. The rough-in requirement makes a system easier and often cheaper to add, but it doesn't mean the home tests low. Given how localized radon levels can be, a new build in La Plata County has the same odds as any other home here.
Can my regular home inspector just run the radon test himself? Only if they hold a Colorado radon measurement license separate from their home inspection license, and only for their own occupied home would the licensing exception apply otherwise. For a transaction, confirm the person conducting the test is licensed under Colorado's rule that took effect July 1, 2022.
Radon isn't a reason to avoid buying in Durango. It's a reason to build your inspection timeline with it in mind instead of treating it as paperwork that trails in after the real decisions are made. If you're weighing a resale property against new construction, or trying to figure out what a radon result should mean for your offer, that's exactly the kind of local detail worth talking through before you're under contract, not after.
If you're thinking about buying or selling in Durango and want a read on what a specific property's history, construction type, or location might mean for something like this, Judi Mora has spent more than 20 years working these streets and can walk you through it. Request a Free Home Valuation to start the conversation.
