From May through September, crawlspaces across Cobb and Cherokee counties get humid. If you have looked under your Marietta or Kennesaw home in the summer and seen condensation or smelled something earthy, you are not alone, and it is not automatically a problem. Here is how to tell the difference between normal seasonal moisture and something worth acting on.

What is normal

  • Higher humidity in summer. Warm, humid Georgia air meets cooler crawlspace surfaces and the relative humidity climbs. Some seasonal swing is expected.
  • A faint earthy smell. A crawlspace over soil will smell like soil. On its own, that is not a red flag.
  • Light, occasional condensation on cold water lines or ductwork during the most humid stretches.

What is not

  • Standing water that does not drain after rain, or any puddle that should not be there. That points to drainage, grading, or a plumbing source.
  • Persistent humidity above roughly 70 percent, which can show up as a damp vapor barrier, beads of water on surfaces, or a musty rather than earthy smell.
  • Wood that is wet to the touch, darkening, or soft. Moisture reaching the structure is worth understanding sooner rather than later.
  • A spike in indoor humidity or new pest activity upstairs, which can be the first sign that the crawlspace is feeding the rest of the house.

What the numbers mean

If you have a humidity reading or a moisture meter reading from your crawlspace, here is a rough guide. These are rough reference points drawn from research and moisture-meter guidance, not hard limits.

Relative humidity (the air)

  • Below about 60 percent: dry. Well-sealed crawlspaces in North Carolina research stayed near this level even in summer.
  • 60 to 70 percent: worth watching, especially if it stays there for weeks. Not alarming on its own.
  • Above about 70 percent for weeks at a time: sustained humidity at this level raises the risk of mold growth. Vented crawlspaces in the same research often ran above 80 percent in summer.

Wood moisture content (the framing)

  • Low-to-mid teens: healthy for floor framing.
  • Above about 16 percent: mold becomes possible.
  • Around 20 percent and up: decay becomes possible over time.
  • Near 28 percent and above: the wood is at fiber saturation, and decay is often present.

One reading is a snapshot. Humidity in a Georgia crawlspace swings with the weather, so the trend over a season tells you more than any single number. That is one reason a baseline assessment is useful: your Kachug report records humidity in the video, so you have a reference point to compare against next summer.

If your numbers are high, the next question is why. Vapor barrier, dehumidifier, or full encapsulation explains which fix matches which cause. If you can smell it upstairs, see musty smell in the house? Check the crawlspace first.

How to think about it

Moisture is a spectrum, not a yes-or-no. The useful question is not whether there is any moisture, because there almost always is. The useful question is whether moisture is reaching the things that matter, and whether it is getting worse. That is exactly what an assessment is for: a clear baseline of what your crawlspace looks like now, so next summer you can tell whether anything has actually changed.

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