1. Yes, Townhomes Get Radon
The misconception that townhomes are immune to radon is surprisingly common. Some people assume that because townhomes share walls and have smaller footprints, they somehow avoid radon. This is not how radon works.
Radon comes from the soil. Any home with a foundation in contact with the ground, whether it is a 5,000 square foot estate or a 1,200 square foot townhome, can have elevated radon. The size of the foundation does not determine whether radon enters. The soil beneath the foundation, the geology of the area, and the condition of the slab are what matter.
Atlanta area townhomes sit on the same granite and gneiss geology as single-family homes. The uranium content in the rock beneath a townhome development is the same as beneath the detached homes down the street. The radon production rate is identical.
In fact, some characteristics of townhomes can actually increase radon risk. Newer townhomes tend to have very tight building envelopes for energy efficiency, which means less natural air exchange to dilute radon. And townhomes with garage levels below the living area can have significant radon accumulation in those enclosed below-grade spaces.
2. How Radon Enters Townhomes
Radon enters townhomes through the same pathways it uses in any other home: cracks in the slab, gaps around utility penetrations, construction joints, and sump pits. The entry mechanisms are identical regardless of the building type.
Slab cracks and joints
Concrete slabs crack over time as they cure and as the soil settles beneath them. These cracks are the primary entry points for radon in most townhomes.
Garage slab penetrations
Many Atlanta townhomes have attached garages at the lowest level. The garage slab is in direct contact with the soil, and any cracks or penetrations allow radon to enter the garage. From there, it can migrate into the living space through the door, walls, and ductwork.
Utility penetrations
Water lines, sewer lines, and electrical conduits that pass through the slab create gaps around them. In townhomes, these penetrations are concentrated in a smaller footprint, which can create multiple entry points in a confined area.
3. Your Neighbor's Levels May Differ
One of the most surprising things about radon in townhome communities is how much levels can vary from one unit to the next. Two units sharing a wall can have dramatically different radon readings. This happens because radon entry depends on the specific conditions beneath each unit's foundation.
Each unit has its own unique pattern of slab cracks, its own utility penetrations in different locations, and its own HVAC system creating its own pressure dynamics. The soil beneath each unit may also vary slightly in composition and permeability, even within the same development.
This means your neighbor's radon test results tell you nothing about your own home. Even if every other unit in your row tested low, your unit could be elevated. And vice versa. Every unit needs its own independent test.
Do Not Rely on Community Tests
Some townhome communities have had one or two units tested and assumed the results apply to all units. This is not valid. Each unit must be tested individually. A test in unit A provides no information about unit B, even if they share a wall and were built at the same time by the same builder.
4. Testing Your Townhome
Testing a townhome follows the same process as testing any other home. A professional radon test involves placing a continuous monitor in the lowest livable area of your unit for 48 hours under closed-house conditions.
In a typical Atlanta townhome with a garage at the lowest level, the test is placed on the main living level above the garage. If the lowest level includes a bedroom, office, or living area (not just the garage), that is where the test goes. The garage itself is not typically tested unless it has been converted to living space.
During the test, keep your windows and exterior doors closed as much as practical. Run your HVAC normally. Normal entry and exit through the garage door or front door is fine. You do not need to avoid the space during testing.
5. Mitigation for Townhomes
If your townhome tests above 4 pCi/L, a sub-slab depressurization system is the standard solution. The installation in a townhome is similar to a single-family home, but the routing of the exhaust pipe may need some creative planning due to shared walls and limited exterior wall space.
Common routing options include running the pipe up the rear exterior wall of the unit, through the garage and up through the attic, or through an interior closet to the roof. The goal is always to vent the radon above the roofline where it disperses harmlessly into the atmosphere.
The suction point is typically installed in the garage slab or the lowest-level slab, depending on your townhome's layout. A single suction point is usually sufficient for a townhome because of the relatively small foundation footprint.
Townhome-Friendly Systems
Modern radon mitigation systems are designed to be discreet and quiet. The exterior pipe is typically 3 to 4 inches in diameter and painted to match the building. The fan, mounted in the attic or exterior, produces minimal noise. Most townhome installations can be completed in one day. Learn more about how radon fans work and contact our residential radon services team for a townhome assessment.
6. HOA and Shared Wall Considerations
Most townhome communities have homeowners associations with rules about exterior modifications. Before installing a radon mitigation system, check your HOA covenants and submit a modification request if required.
In our experience, HOAs almost always approve radon mitigation systems because they address a documented health hazard. Framing the request around health and safety, and providing documentation of your elevated test results, typically leads to quick approval.
If your HOA is resistant to exterior piping, discuss interior routing options with your radon professional. Running the pipe through the garage, up through an interior wall, and out through the roof is an option that avoids visible exterior modifications on the front or sides of the building.
Regarding shared walls, your radon system only affects your unit. The sub-slab depressurization system creates a vacuum beneath your slab specifically. It does not draw radon from your neighbor's unit or affect their levels. Similarly, your neighbor's system (or lack thereof) does not affect your unit.
