Radon in condos and townhomes: who should test, who fixes it, and how HOAs handle it

Radon guidance is usually written for single-family houses, where the owner controls the whole building. Condos and townhomes are different. You share walls, foundations, and sometimes ventilation systems, and the soil beneath your unit may be common property owned by the association. That affects who should test, who decides on mitigation, and who pays. This guide walks through the practical questions.

Which units are most at risk?

Radon comes from the soil, so units in contact with the ground are the most likely to have elevated levels:

• Ground-floor and garden-level condo units.
• Townhomes, which usually have their own slab, basement, or crawl space.
• Units above unvented crawl spaces or parking garages built on soil.

Upper-floor units are generally lower, but not always. Elevator shafts, stairwells, plumbing chases, and shared HVAC systems can carry soil gas upward. EPA notes radon is easily moved by air currents and pressure, and in buildings with forced-air systems it can be distributed widely.

Testing in a condo or townhome

• Test in your own unit's lowest lived-in level. For townhomes, that may be a finished basement.
• Follow closed-house conditions for short-term tests: windows and exterior doors closed, except for normal entry and exit, for 12 hours before and during the test.
• Place the device in a living area or bedroom, about 20 inches or more above the floor, away from drafts and exterior walls.
• Confirm any result at or above 4 pCi/L with a second test.

If neighbors are willing, testing several ground-contact units at the same time gives the association a much clearer picture.

Why mitigation often involves the association

In a single-family house, you'd simply hire a mitigator. In a condo or townhome community, several issues come up:

• Ownership. The slab, foundation walls, roof, and exterior walls may be common elements owned or maintained by the association. Drilling through a slab, running a pipe up an exterior wall, or penetrating the roof usually requires association approval.
• Shared foundations. In attached townhomes, sub-slab suction under one unit can affect neighbors. Some buildings need a system designed for the whole row.
• Roof discharge. EPA explains radon must be vented above the roof, because discharge concentrations are high and fall to near background within a few feet. In multistory buildings, routing a pipe to the roof is a bigger job and may cross other units or common areas.
• Architectural rules. Exterior pipes and fans may need design approval.

How to raise radon with your HOA

1. Read your governing documents to see who maintains the slab, foundation, and exterior, and what the approval process is for alterations.
2. Share your results in writing with the board or manager: the dates, test type, lab report, and EPA's guidance to fix at 4 pCi/L or higher.
3. Ask whether the association has tested other units or common areas.
4. Propose next steps: building-wide testing of ground-contact units, then a professional assessment by a qualified mitigator.
5. Ask how costs will be handled. Associations may treat radon mitigation as a common expense, an owner expense with approval, or a mix, depending on the documents and state law.

If you're allowed to mitigate your own unit

Some associations approve individual systems for townhomes or ground-floor units. If so:

• Get written architectural approval before work begins.
• Hire a qualified mitigator, and ask your state radon office about licensing requirements.
• Confirm the fan location (outside living space), discharge above the roof, warning device, and labeling.
• Agree in writing who maintains the system, and what happens when the unit is sold.
• Run a post-mitigation test within 30 days of installation, but no sooner than 24 hours after the system starts, as EPA's guide advises.

Buying a condo or townhome

If you're buying a ground-contact unit, add radon to your due diligence:

• Ask whether the unit or building has been tested, and for the results.
• Test during the inspection period if possible.
• Ask the association about any existing mitigation systems, and who maintains them.
• Check the governing documents for rules on alterations to the slab or exterior.

Renters in condos

If you rent a condo unit, the owner, and possibly the association, would need to approve and arrange mitigation. Test, share results with your landlord in writing, and check your state's landlord radon rules. See radon in rentals and apartments.

Questions to ask your association

• Has the association ever tested units or common areas for radon? Can owners see the results?
• Who maintains the slab, foundation walls, roof, and exterior under our governing documents?
• What's the approval process for a radon system, and how long does it take?
• Would the board consider building-wide testing of ground-contact units?
• If mitigation is needed in several units, will the association coordinate one design?
• How will installation, electricity for fans, and maintenance costs be shared?
• How will existing systems be documented for future buyers?

Getting answers in writing helps avoid disputes later, especially when units change hands.

The bottom line

Shared buildings make radon a group project. Test your unit, share results, and work with your association on a building-appropriate solution. EPA estimates radon causes about 21,000 lung cancer deaths a year in the United States, so it's worth the effort to get it right.

Key takeaways

• Ground-contact units, including townhomes and ground-floor and garden-level condos, are the most likely to have elevated radon.
• Test your own unit's lowest lived-in level, and confirm any result at or above 4 pCi/L.
• Slabs, foundations, and roofs are often common elements, so mitigation usually needs association approval.
• Attached buildings may need a system designed for several units, with discharge above the roof.
• Put approvals, maintenance responsibilities, and cost sharing in writing.
• Buyers should ask for test results and documentation of any existing systems.
• Coordinated, building-wide testing gives boards the clearest picture for decisions.