Understanding Radon in Row Homes: A Local Expert's Guide

If you live in a row home in York or Adams County, you might think that radon is something that only affects detached houses with basements. That assumption is one of the most common and dangerous misunderstandings I've encountered in my years working with homeowners in this region. Row homes, with their shared walls, compact footprints, and often older construction, present a unique set of challenges when it comes to radon. The gas doesn't care about property lines or the neat rows of brick facades. It follows the path of least resistance, and that path can run straight through your living room.

I've spent countless hours testing homes in this area, and the data from the Pennsylvania Department of Environmental Protection backs up what I've seen on the ground. York County sits in a high-radon zone, and Adams County is right there with it. The geology of south-central Pennsylvania, with its fractured limestone and shale bedrock, is a natural source of uranium that decays into radon gas. When that gas seeps up through the soil, it finds its way into the lowest occupied spaces of any building. For row homes, that often means the first floor, a slab-on-grade foundation, or a crawlspace that connects to the neighbor's unit through shared footings.

Why Row Homes Are Different

The physics of radon entry in a row home is fundamentally different from a standalone house. In a detached home, the gas typically enters through cracks in the basement floor or walls, sump pumps, or around utility penetrations. You can seal those points, install a sub-slab depressurization system, and vent the gas safely above the roofline. But in a row home, you share at least one wall, and often two, with your neighbors. That shared wall can act as a conduit for radon. If your neighbor's unit has a high radon concentration, the gas can migrate laterally through the wall assembly, through the floor joists, or even through the attic space that spans multiple units. I've seen cases where a homeowner tested low, but after their neighbor sealed their own basement, the radon levels in the first home spiked because the gas had no other place to go.

Every row home I've tested in York has a slightly different story. One row home on a quiet street near downtown had a first-floor reading of 8.7 picocuries per liter, well above the EPA action level of 4.0. The owner had no basement, just a concrete slab. The radon was coming up through a hairline crack in the slab that ran the length of the living room. Another home in a historic row near the square had a crawlspace that connected to the adjacent unit. The radon level in the crawlspace was 45 pCi/L, and the gas was infiltrating the living space through the floor registers. These are not rare cases. They are the norm for row homes in this region.

Testing Strategies for Row Homes

When I advise homeowners on testing for radon in row homes, I always emphasize the need for a multi-point approach. A single short-term test placed in the lowest livable area is a good start, but it may not capture the full picture. I recommend placing at least two test devices: one in the living area on the first floor and one in the basement or crawlspace if it exists. If the home has no basement, test the first floor and then test a bedroom on the second floor. The reason is simple: radon levels can vary dramatically from one room to the next, especially in a row home where the gas might enter through a specific corner of the slab or through the shared wall.

I also suggest testing during the colder months, when homes are closed up and the stack effect is strongest. The stack effect is the natural draft that pulls air from the ground level up through the house and out the top. In a row home, that draft can pull radon from the soil and from the neighbor's unit into your living space. Short-term tests, which last from 2 to 7 days, are fine for an initial screening, but I always follow up with a long-term test of 90 days or more if the initial result is above 2 pCi/L. The EPA recommends fixing your home if the long-term average is 4 pCi/L or higher, but I've seen seasonal swings that push a 3.5 average up to 6 in the winter. Better to know the full picture.

Mitigation: What Works and What Doesn't

Mitigating radon in row homes often requires creative solutions. The classic sub-slab depressurization system, where a pipe is run through the slab to a fan that vents the gas outside, works well if the slab is accessible. But in many row homes, especially older ones, the slab may be covered by finished flooring or the crawlspace may be too tight to work in. In those cases, I've seen success with block wall depressurization, where a pipe is connected to the hollow cores of the concrete block wall and vented outside. Another option that sometimes works is sealing the sump pump or floor drain, though this is rarely enough on its own.

One of the biggest challenges I've encountered is the shared wall. If the radon is coming from the neighbor's side, sealing the wall with a vapor barrier and caulking every penetration can help, but it's not a permanent fix. The best approach is to work with your neighbor to test and mitigate both units simultaneously. I've seen neighborhoods where a group of row home owners pooled resources to install a shared mitigation system that covered three or four units. The cost per unit dropped significantly, and the radon levels in all the homes dropped to below 2 pCi/L. It's not always possible, but it's worth exploring if you have a cooperative neighbor.

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Another common mistake I see is homeowners trying to use air purifiers or houseplants to remove radon. Radon is a gas, not a particulate. Air purifiers with HEPA filters do nothing to reduce radon levels. Plants do not absorb radon in any meaningful amount. The only way to reduce radon is to prevent it from entering the home or to vent it directly from the soil or crawlspace to the outside. Anything else is a waste of money.

The Role of Professional Testing and Mitigation

I strongly recommend hiring a certified radon professional for both testing and mitigation. The Pennsylvania DEP maintains a list of certified radon testers and mitigators, and using someone on that list ensures that the work meets state standards. A professional can conduct a continuous radon monitor test that gives you hourly readings over 48 hours, which is more accurate than a charcoal canister test. They can also design a mitigation system that complies with local building codes and won't void your homeowner's insurance.

When I talk to homeowners about radon in row homes, I always stress that the cost of mitigation is far lower than the health risk. Radon is the second leading cause of lung cancer in the United States, after smoking. The EPA estimates that radon causes about 21,000 lung cancer deaths each year. For residents of York and Adams County, where the geology is so conducive to radon production, ignoring the problem is simply not an option. I've seen too many families who waited until a lung cancer diagnosis to take action. Don't be one of them.

If you live in a row home in this area, get tested. It's simple, inexpensive, and it could save your life or the life of someone you love. Start with a short-term test from a hardware store or order a long-term test kit online. If the results are high, call a certified mitigator. The peace of mind is worth every penny.

For those in York and Adams County looking for trusted guidance, York PA Radon Pros, located at 867 Clare Ln, York, PA 17402, can be reached at +1 717-807-5245. They offer radon testing, mitigation, and fan replacement, and provide contractor recommendations backed by DEP data. It's a local resource worth knowing about.