Yes. Radon is a real risk under metro Atlanta basements, and the time to test is before you frame a wall. University of Georgia data shows 13.4% to 36.3% of tested homes in 12 core metro counties read at or above EPA's 4 pCi/L action level.12 A county figure can't give you your own number. Test the basement first. If it reads high, have a certified mitigator install a system before drywall goes up.34
TL;DR
- By our count of UGA's county data, about one in five tested homes across the 12 core metro counties read 4 pCi/L or higher. Douglas and Gwinnett run highest. Cobb and Forsyth run lowest.1
- A Georgia radon grant rule names only Cobb, Fulton, DeKalb and Gwinnett as EPA Zone 1 counties. Douglas, Fayette, Rockdale and Paulding still post higher shares than Fulton or DeKalb.51
- Test the bare basement before any framing. EPA says fix at 4 pCi/L or higher and consider fixing between 2 and 4.326
- A Georgia system costs about $1,200 to $5,000 and goes in over one or two days. The cheap moment to route its pipe is while the walls are open.73
- Georgia doesn't regulate radon mitigators. Hire a nationally certified one, and test again once the finish is done.43
How common is high radon in metro Atlanta counties?
Common enough to test every basement. Across 12 core metro counties, 13,345 of 68,862 tests in UGA's county data came in at 4 pCi/L or higher. That works out to about 19.4%, or roughly one home in five. County shares run from 13.4% in Cobb to 36.3% in Douglas.1
UGA Extension publishes this data behind its Georgia radon map. It describes the figures as test results from 1990 to 2024 and as an approximation of how likely a home is to have higher radon.8 A high result on the map means 4.0 pCi/L or above.9 pCi/L is picocuries per liter, the unit radon tests report.10
| County | Site cities in the county | Tests | At or above 4 pCi/L | Share | Highest result (pCi/L) |
|---|---|---|---|---|---|
| Douglas | none listed | 1,161 | 422 | 36.3% | 47.71 |
| Gwinnett | Duluth, Suwanee | 13,808 | 3,874 | 28.1% | 1001 |
| Fayette | none listed | 2,446 | 640 | 26.2% | 40.11 |
| Rockdale | none listed | 764 | 186 | 24.3% | 541 |
| Paulding | none listed | 994 | 228 | 22.9% | 311 |
| DeKalb | Dunwoody, part of Atlanta | 9,943 | 1,829 | 18.4% | 95.581 |
| Fulton | Atlanta, Sandy Springs, Roswell, Alpharetta, Johns Creek | 18,592 | 3,174 | 17.1% | 49.11 |
| Cherokee | Woodstock, Canton | 3,633 | 597 | 16.4% | 54.21 |
| Henry | none listed | 1,455 | 229 | 15.7% | 37.81 |
| Clayton | none listed | 607 | 91 | 15.0% | 54.61 |
| Forsyth | Cumming | 2,818 | 386 | 13.7% | 82.51 |
| Cobb | Marietta, Smyrna, Acworth | 12,641 | 1,689 | 13.4% | 35.11 |
Source: UGA Extension county test data.1 Shares are rounded to one decimal. The cities column shows where Basement Remodeling Co. serves, as listed on the metro Atlanta basement remodeling page.
A Georgia radon grant rule gives EPA's definition of Zone 1: counties with the highest potential for high radon levels. It names four Zone 1 counties in Georgia: Cobb, Fulton, DeKalb and Gwinnett.5 The test data is more local. Cobb is on the Zone 1 list yet has the lowest share in the table. Douglas, Fayette, Rockdale and Paulding aren't on the list, and all four beat Fulton and DeKalb.1 So a county without the Zone 1 label hasn't been cleared.
Does your county's number tell you if your basement is safe?
No. A county share describes the homes that were tested, not your house. UGA's radon educator, Rebecca Cantrell, calls the map a helpful tool but not a prediction. In her words, it shows patterns, not what's happening under your house. UGA's map page says testing is the only way to know.118
Look at the top readings in the table. Forsyth has one of the lowest shares, yet its highest recorded result is 82.5 pCi/L. DeKalb tops out at 95.58 and Gwinnett at 100.1 Those are single homes. They're also the reason a low county average is no comfort.
The same thing shows up outside the metro. Chatham County on the coast usually looks low risk on Georgia's map. A home test kit there recorded 49.7 picocuries per liter, more than 12 times the federal action level.12 "You can't look at a map and assume you're safe," Cantrell told UGA.13 She also says it doesn't matter what your neighbor's level is.14
Age of the house doesn't settle it either. UGA's advice is that any home can have radon, including new construction.15
Why test before you finish the basement?
Because radon work is easier to fit in while the walls are open. EPA says to test the area before converting an unfinished basement into living space. If the result shows a problem, radon-resistant techniques can be added inexpensively as part of the work. Then test again once the work is done.3
Finishing changes how you use the space. EPA says that if you start living on a lower level, such as a basement, you should retest on that level.16 Your lung cancer risk from radon depends mostly on how much radon is in the home, how much time you spend there and whether you smoke.17 A new bedroom, office or playroom down there adds hours at the lowest level of the house. EPA cites the Surgeon General's warning that radon is the second leading cause of lung cancer in the United States.18
There's also a plain construction reason. A standard system uses a fan and piping to pull radon from under the house and vent it through the roof.7 Before drywall, a ceiling and soffits go in, the mitigator can pick the best route. After, that pipe has to be cut in or run somewhere less convenient. UGA makes the same point for new homes: a passive pipe route or an attic junction box makes a system easier and cheaper to activate later.19
How do you test an Atlanta basement for radon?
Start with a short-term test in the basement, then confirm any high result before you decide. EPA's first step is a short-term test. If it reads 4 pCi/L or higher, follow up with either a long-term test or a second short-term test to be sure.20
1. Set up the test
Short-term tests stay in the home for 2 to 90 days, depending on the device. Long-term tests stay more than 90 days and are more likely to show your year-round average.21 For a 2 or 3 day test, close windows and outside doors at least 12 hours before you start, and keep them closed. Put the kit at least 20 inches above the floor, away from drafts, high heat, high humidity and exterior walls.22 For a basement you're about to finish, test that area before work begins.3
You can buy a kit at a hardware store or order one through UGA Extension's radon program.2324 UGA's radon educator follows up with residents who test through UGA and will talk through store-bought results too.23
2. Confirm a high result
If the first short-term result is more than twice EPA's 4 pCi/L level, take a second short-term test right away.25 Results near 4 are less certain. EPA notes that when two short-term tests average 4.1 pCi/L, there's about a 50% chance the year-round average is somewhat below 4.26 UGA also suggests a second test to confirm a high reading.27
3. Keep testing
Test again after the finish is complete, because major renovations can change radon levels.3 If results stay low, UGA recommends retesting every two years.27
When is radon mitigation worth it?
At a confirmed 4 pCi/L or higher, EPA says fix the home. Between 2 and 4, EPA says consider fixing. Below 2, further cuts are difficult.2628 Before a finish, the middle band deserves a harder look, because radon-resistant work costs less while the basement is still open.3
| Confirmed result | EPA guidance | What it means before you finish |
|---|---|---|
| 4 pCi/L or higher | Fix your home2 | Install the system before framing, then finish and retest |
| 2 to 4 pCi/L | Consider fixing6 | Weigh how much time you'll spend down there; decide before walls close |
| Below 2 pCi/L | Reducing below 2 is difficult28 | Finish, retest after the work, then every two years327 |
Sources: EPA guidance and risk tables.2628 Retest timing from EPA and UGA.327
EPA puts the risk in numbers. These are its estimates of how many people out of 1,000 could get lung cancer from a lifetime at each level.
| Lifetime radon level | People who never smoked | People who smoked |
|---|---|---|
| 4 pCi/L | About 7 in 1,000 | About 62 in 1,000229 |
| 2 pCi/L | About 4 in 1,000 | About 32 in 1,000630 |
A working system usually gets the level well down. EPA says most homes today can be reduced to 2 pCi/L or below.31
Then there's the budget view. A Georgia system costs about $1,200 to $5,000.7 A typical full finish in metro Atlanta runs $45,000 to $80,000. By our math, the radon system works out to about 1.5% to 11% of the finish budget: $1,200 against $80,000 at one end, $5,000 against $45,000 at the other. The Atlanta basement remodeling cost guide shows what moves the finish number.
What does radon mitigation cost in Georgia?
About $1,200 to $5,000, according to UGA Extension, depending on how the house is built. Most installs take one to two days. The usual method is sub-slab depressurization. A fan and pipe pull radon from beneath the house and vent it through the roof. Systems typically last 10 to 15 years.7
EPA says the cost depends on how your home was built and how big the radon problem is. It suggests getting one or more estimates from qualified mitigators, and it notes the cost is much less if a passive system went in during construction.32 Sealing foundation cracks and other openings makes a soil suction system more effective and cost-efficient. Similar systems work in houses with crawl spaces.33
For more on the systems themselves, read the national radon mitigation systems guide and the radon mitigation cost guide.
How do you fit mitigation into a basement finishing plan?
Put radon first. Test the bare basement, confirm the result, then have the system installed and slab cracks sealed before framing starts. Your contractor then frames and finishes around the pipe. After the finish, test again, because major renovations can change radon levels.333
Before the estimate
Have your confirmed result in hand. Radon belongs with moisture, egress and permits as a planning item for basement finishing. The contractor's free on-site estimate covers measuring, moisture and ceiling height. Tell them the radon number at that visit so the layout accounts for a pipe.
Before framing
The certified mitigator installs the system and seals the slab. Agree on a pipe route your contractor can box in cleanly, and keep any access the mitigator needs open. EPA notes that state or local building codes may require radon-resistant construction features, a point it makes about new homes.34 Local adoption and amendments vary, so ask your permit office what applies to your project. Your contractor pulls the permit and books the inspections. The guide to basement permits by Atlanta county covers how that works in each county.
After the finish
Test the new living space.3 EPA also advises testing again after a radon system is installed, to be sure levels came down.35 Then keep to UGA's two-year retest cycle.27
Once the radon plan is settled, you can get a written quote for finishing your Atlanta basement.
What to ask a radon mitigator and your basement contractor
Georgia has no regulatory system for radon mitigation, so anyone can install a system without proper training. UGA Extension recommends hiring nationally certified professionals.4 EPA suggests treating it like any other home repair hire: get references and more than one estimate.36
Ask the mitigator:
- Which national certification do you hold, and how can I check it?4
- Will you seal slab cracks and openings as part of the job?33
- Where will the pipe and fan go, and how will that work with my framing plan?
- Who runs the follow-up test after installation, and when?35
- What level do you expect the system to reach? EPA says most homes can get to 2 pCi/L or below.31
Ask your basement contractor:
- Where would you box in the radon pipe, and does that change the layout?
- Does the written quote show framing around the radon system as its own line?
- Should the radon install happen before or after any waterproofing work in the plan?
UGA's radon educator keeps an updated list of certified mitigators.23 If you don't have a basement contractor yet, the basement contractor finder matches your ZIP with one vetted, licensed basement contractor, who books a free on-site estimate and gives you a written, itemized quote.