Five Things to Settle Before a Nashville Crawl Space Is Sealed

Test for radon first: Metro Public Health says about 40 percent of the 4,152 homes tested in Davidson County showed elevated levels. Then plan the drying method for summer air, solve any standing water, ask whether Metro Codes needs a permit, and check the contractor's Tennessee license on verify.tn.gov.

1. Radon

Metro Public Health notes that the EPA lists Davidson County as an area with high potential for elevated radon, and that about 40 percent of the 4,152 homes tested in the county showed elevated levels; the page cites the EPA action level of 4 picocuries per liter. A short test before the crawl space is sealed gives you a baseline; a second test afterward shows whether anything changed. If the result is high, ask whether radon mitigation can be built into the same job.

2. The summer air

Averaged from NOAA's 1991–2020 hourly normals at Nashville International Airport, the dew point sits at 64.6°F in June, 68.0°F in July and 66.6°F in August. A sealed space still needs a way to remove that moisture. A dedicated crawl space dehumidifier is the most common choice; conditioned air ducted from the house system is another, and involves HVAC work.

3. Rock, soil and standing water

The USDA describes the Nashville Basin's bedrock as Ordovician limestone, with sinkholes common and outcrops in many areas, and its limestone flats as silt loam to silty clay soils 22 to 60 inches deep. Water that can't soak into rock moves sideways, sometimes into a crawl space. If you have seen puddles after storms, a drain or sump comes before plastic. Rotted wood gets fixed at the same stage; see crawl space repair.

4. Does sealing a crawl space need a Metro permit?

Metro Nashville Codes lists the 2024 International Residential Code among the codes it has adopted, with local amendments. That code has its own section on unvented crawl spaces. Whether your job needs a permit depends on the work, especially if wiring or ductwork is added, so ask the specialist who will pull it, or call Metro Codes before work starts.

5. The contractor's license

Tennessee's Board for Licensing Contractors requires a contractor's license for projects of $25,000 or more. Below that, Davidson County is one of nine counties where a Home Improvement license is required for residential remodeling projects from $3,000 to $24,999. Ask for the number, check it on verify.tn.gov, and compare the written price with the 2026 crawl space encapsulation cost ranges.