Radon in Townhouses and Condos: Who Is Responsible?

If you live in a townhouse or condo, you might assume radon is someone else's problem. After all, radon rises from the ground, and maybe your unit is on the third floor. But that assumption gets a lot of people into trouble.

Can Condos and Townhouses Actually Have Radon?

Yes. The EPA is clear on this: any home with ground contact can have elevated radon. That includes townhouses with slab-on-grade foundations, condo units over basement-level parking garages, and any unit that sits directly on soil. Radon enters through cracks in the slab, gaps around utility penetrations, and seams where walls meet the foundation — the same pathways it uses in a detached house.

Upper-floor units are generally lower risk, but not zero risk. Radon can migrate through elevator shafts, stairwells, and shared utility chases. If you are on the first or second floor, testing is worth the small cost. For a deeper look at how radon behaves and why it matters, check our guide to radon gas.

So Who Pays for Testing?

This is where things get political. In most condo associations, the answer depends on what your governing documents say — and many of them say nothing at all about radon.

Here is how it typically shakes out:

• Individual unit owners are usually responsible for testing inside their own unit. A short-term test kit costs $15 to $40, and professional testing runs $150 to $300.
• HOAs or condo boards may be responsible for common areas, shared structural elements, and building-wide mitigation if the problem originates from shared infrastructure.
• Tenants in rental condos should ask their landlord, but most states place the testing obligation on the property owner, not the renter.

The practical reality? Many HOAs resist taking on radon because it opens a liability conversation they would rather avoid. If your board pushes back, pointing them to the EPA's guidance on multifamily buildings can help. The EPA recommends that all ground-contact units in multifamily buildings be tested.

What About Real Estate Transactions?

When a condo or townhouse changes hands, radon testing often comes up during inspection. The buyer's inspector may flag elevated levels, and suddenly there is a negotiation about who fixes it. In most cases, the seller is expected to address the issue or provide a credit — the same as with a single-family home. Our mitigation cost guide covers what those fixes typically run.

Mitigation in Multi-Unit Buildings: The Complications

Mitigating radon in a townhouse or condo is fundamentally the same science as in a detached home — you are pulling radon from under the slab and venting it above the roofline. But the logistics get harder when walls, slabs, and airspaces are shared.

Sub-Slab Depressurization in Shared Structures

In a townhouse row, the concrete slab often runs continuously under multiple units. That is actually good news for mitigation — a single sub-slab depressurization system can sometimes cover two or three units if the soil permeability is decent. But it also means you may need your neighbor's cooperation, or the HOA's approval, to route piping or install a fan.

For buildings with separate slab pours per unit, each unit may need its own suction point. This is common in newer townhouse construction where fire-rated walls extend down to the footing.

Crawlspace Units

Some townhouse complexes have crawlspaces under ground-floor units. These typically require sub-membrane depressurization — a heavy poly sheet sealed over the dirt floor with suction piping underneath. If the crawlspace is shared between units, the HOA usually needs to coordinate the install.

Vent Pipe Routing

In a single-family home, the vent pipe runs up through a closet or garage and exits through the roof. In a condo, that route might pass through another unit's space, or the HOA may have rules about exterior pipe visibility. Some buildings require interior routing with a rooftop exit; others allow exterior wall-mount with the discharge point above the eave line. Either way, you need approval before drilling.

Dealing with Condo Board Politics

Let's be direct: getting an HOA to act on radon can be frustrating. Board members worry about cost, liability, and setting precedent. Here is what works:

• Start with data. Test your unit and share the results with the board in writing. Numbers are harder to ignore than vague concerns.
• Reference EPA guidance. The EPA recommends fixing any home with radon at or above 4.0 pCi/L. That applies to condos and townhouses equally.
• Get multiple quotes. If you can present the board with actual mitigation proposals from certified radon professionals, the conversation shifts from abstract worry to concrete planning.
• Propose cost-sharing. If the system benefits multiple units, a shared cost arrangement is often the fairest path forward.

If the board refuses to act and your unit tests above the EPA action level, you may have legal options depending on your state. Some states have specific radon disclosure or remediation requirements for multifamily buildings. Consulting a real estate attorney familiar with your state's radon laws is a reasonable next step.

What About Upper-Floor Units?

According to the EPA, the risk drops significantly above the second floor in most buildings. But "significantly lower" is not "zero." Stack effect — where warm air rises and pulls replacement air from lower levels — can draw radon-laden air upward through the building envelope. If you are on an upper floor and curious, a $15 test kit settles the question in a few days.

For more on what radon levels mean and when to act, our radon levels and safety guide breaks down the numbers.

Bottom Line for Condo and Townhouse Owners

Radon does not care about property lines or HOA bylaws. If your unit touches the ground, test it. If the result is 4.0 pCi/L or higher, push for mitigation — whether that means working with your board, splitting costs with neighbors, or handling your own unit independently. The fix is the same proven technology used in millions of homes. The only real barrier is getting the right people to agree it needs doing.