My home is 14 years old. I have been using a 40 pint dehumidifier at 50% until this spring. It was only after discovering mild amount of mold under my fiberglass insulation that I felt I needed to improve upon what I had.

My basement is almost 3000 sq. ft. I had purchased 2 70pt. dehumidifiers, placing them on opposite areas of the basement. (as I found the humidity was different in one area than the other).

The humidity now is between 40 - 45% where it was at 67% with first utilizing the new humidifiers.

I have noticed cracks that were not present in my walls and floors before, beginning at a 55% humidity level in the basement. I have a neighbor who uses 2 70 pt. units in a smaller basement at a lower humidity level with no complaints, so I was surprised by this change.

It has been 4 months later and the cracks have stabilized.

Any thoughts on why this would occur?

  • 1
    Your home is 14 years old, cracks are expected, we cannot know specifically WHY they occurred.Did adding a dehumidifier "help" it to crack, "sure" it could, as the air is dryer, the concrete can cure more. It is said that concrete never fully cures, as it always has some moisture in it. It is probably best that you do more of an assessment of the area around the home. What kind of soil does your area have? Are you on a hill? Has it been very wet or dry? climate changes and settling do impact concrete. Just keep an eye on it. Any drastic changes even over a time, should be inspected immediately
    – noybman
    Sep 23, 2017 at 21:06
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    If you’re getting this much moisture, it may be good to address drainage and runoff from the outside. Make certain the grade near the house always directs water away from the foundation, and that all gutters and downspouts are in working order. most people don't realize that most water stays at the surface and runs downhill. If the downhill encounters a foundation that gives it a place down instead of remaining as surface water. Divert the surface water, and you'll be able to retire the dehumidifiers.
    – Tyson
    Sep 24, 2017 at 0:56
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    I suspect the dehumidifiers are a response to the problem causing the cracking rather than the cause, themselves. As Tyson indicates, it's likely that there's external water that's not only the cause of the mold, but the cracking as well. It can be from the pressure of the water, and/or the water is undermining the supporting soil, causing settlement cracks. The shape and location of the cracks can be diagnostic. Can you post some photos at a sharing site, like imgur.com, and provide a link? You could also ask a friend who is familiar with concrete or foundation issues to look at it.
    – fixer1234
    Sep 24, 2017 at 22:22
  • BTW, you'll stop the mold when you get the humidity down to the 50-60% range (usually marked "normal" on the dial). Dehumidifiers are very inefficient when you run them much below that. You'll run up your electric bill without providing additional benefit.
    – fixer1234
    Sep 24, 2017 at 22:26
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    Thank you for your responses! The soil around our home is clay. Cracking of the soil is seen with little rain. We have 4 ft downspouts that are clean, grading is flat due to soil being close to Hardie Plank siding. I fixed our sump pump line that had a leak near the house and mudjacked a slab that caused draining towards the home. The back of our lot drops 8 ft towards a pond that is lower than the drain tiles.
    – Suzanne
    Sep 25, 2017 at 2:27

1 Answer 1


Thank you.

I have been following up on the cracks, they have stabilized. I had a basement structural engineer review them along with the integrity of the walls and floor, no structural problems. I used a joint/crack concrete sealant laying down a backer rod first which has remained unchanged.

May have pulled moisture too quickly with changing to 2 more efficient dehumidifiers as no cracks were noticed prior to this change.

Using concrete sealant to decrease likelihood of additional drying/crackingof concrete.

  • It seems that you have created two accounts on this site. Merging them would be a good idea so that you can keep track of all your posts and whatnot :) Feb 16, 2018 at 1:00
  • Thanks for closing the loop on your problem. Just to add to ThreePhaseEel's comment on merging accounts, separate accounts will interfere with editing your own posts, commenting on your own thread, and accepting answers, so it's a lot easier to get things done on the site if you get them merged. BTW, if you accept your own answer, that will indicate that the problem has been solved. Under your original user account, or after merging, you will see a checkmark next to the answer. Clicking that will accept it.
    – fixer1234
    Feb 16, 2018 at 2:51

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