I am looking to rent a basement. My purpose is to store documents and clothes, for several years. Hence I need to be sure that this basement is dry, that my documents and clothes won’t be damaged over time. I find it hard to see that when visiting the basement. How can I tell ?

  • One way to tell if there is moisture from the floor is to tape a piece of plastic to the floor like a square from a plastic bag. after 24 hours pull the bag up and see if it has water on the bottom side. other than that look for water marks and mold on the walls.
    – Ed Beal
    Apr 28, 2017 at 13:12
  • Thanks guys. Actually my question is not specific to a particular basement, but general, since I am visiting several, and asking myself the question about each of them. I wish I could do the plastic bag experiment, but unfortunately owners are available for a 15 minute visit, they would probably not want to come back one day later to get the experiment's result Apr 30, 2017 at 11:10

2 Answers 2


A humidity measurement is the first line of defense. The relative humidity should be appropriate for the local climate, say 40-50%. If it's higher, find out whether a dehumidifier can be used (with a floor drain, ideally).

If you have an unfinished section of floor, duct tape a square of poly sheeting for a few days and see how much moisture accumulates. This doesn't give you an absolute answer, but it tells you how hard you'll have to work to keep the air humidity down.

Otherwise, look for visual cues. Dark concrete. Staining. Mildew. Of course, you could also ask the owner.


Moisture can also accumulate depending on air circulation. Make sure that there is some sort of air circulation if these documents are critical. You can also fully seal the document containers so that they’re airtight and not impacted as much.

Also temperature differences between various materials could generate moisture. For instance an uninsulated basement with cold duct work for the upstairs will drop any humidity accumulated from warmer moist air. This over time would be the same as a roof leaking on your documents.

Plan on protecting your documents yourself and anything that they provide for your document protection is just added good measures. Good luck.

  • See if the basement air is circulated through the rest of the home, if so the odds of it being dry are much higher. You can get a mold test kit and take samples in moments. Good Luck. More information please!
    – Gil
    Jul 28, 2021 at 22:14

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