Concrete floor questiion

Redfred1

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I have concrete slab (garage) 40+ years old that sweats big time. The previous owner probably did not install a vapor barrier. Any way to seal the floor? I haven't tried anything yet; hopefully there is a cure. I wasn't planning on painting it; just want it dry. I understand its with the humidity; down here it is higher than the tempature
 

Scott Danforth

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if you epoxy coat it, the moisture sits on top and you can almost skate. if your in an area that has large temp swings, and high humidity, you get condensation.
 

Redfred1

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I was hoping for a solution; but I do appreciate the help.
Scott: I was hoping painting was a option. I'm not after a fashion plate garage; just a dry floor to lay on when working on
different things. I installed ceiling tile; it gave me more light.
bd: the garage has no air movement at all. Might get a couple of cheapo ceiling fans;it might help.

My neighbor next door just had a 30X40 steel building built last year. They did install 8mill plastic under the slab. His floor sweats too; he runs 2 floor fans.
Will watch for more opinions.
 

NYBo

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You need to determine whether the moisture is coming up through the slab or is condensation (or both). Dry off a section a couple of feet square. Tape down a piece of clear plastic, making sure to seal all the edges well. Wait a couple of days and pull up the plastic. If the floor is dry, the problem is condensation.
 

roscoe

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If its condensation, you need to dry the air, or heat the slab.

A fan will only bring in more humid air and create more condensation.
 

bigdee

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If its condensation, you need to dry the air, or heat the slab.

You have to warm slab so it is above the dewpoint temperature. Infrared ceiling heaters is one method. Ceiling fans also will help by pushing the warm air that rises back down to floor/slab. Floor fans or box fans or anything to CIRCULATE the inside air will help but it may make it drafty/uncomfortable. If you can afford to keep the AC or heat on 24-7 that would eliminate the problem too. Industrial de-humidifiers are another method but would be expensive. I used to work in a plant with water cooled injection molding machines and controlling dewpoint was a big challenge. The molds cooled by chilled water was a constant so we could not change that,we had to condition the air instead. Sometimes in the hot humid summer we had to keep the plant cold enough that you had to wear a jacket.
 

Redfred1

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All good suggestions. Am trying NY's thing with the plastic. Right now outside temp is 72; DP 67; slab temp is 68. supposed to rain all week; but supposed to be in the 70's. (Fake Spring).
Floor fan .would work; they take up space. Priced some ceiling fans online; nope! Maybe oscillating fans hung from the ceiling. Will wait and see what the plastic shows. Thanks for the thoughts; will keep updated.

I see the IT people are still in Limbo; couldn't login this morning; once I did ;could not bring up "Todays Posts"; or my messages. Just a comment.
 

bigdee

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Right now outside temp is 72; DP 67; slab temp is 68. supposed to rain all week; but supposed to be in the 70's. (Fake Spring).

Wow your slab is just 1 degree away from condensation! Don't you love this southern humidity. When I first moved to the south I thought it was strange to see wet grass every morning with no rain and 90 degree afternoon temperatures!
 

Redfred1

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Just checked: temp 72; humidity 90%; DP 69; slab 69 at 10PM CST. The Admiral and I are a rare bred; both of us were born in Big H; so we are used to it. I'll take the humidity over the single and minus numbers they are get up North.

I should mention that the house is surrounded by a bunch of oak trees; the roof gets little or no Sun; helps the light bill.
Floor is cool;but dry.
 

mickyryan

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fan does work i Build 2nd floor swimming pools and guy thought he had a leak it was humidity as soon as he put ventilation the " leaks" mostly stopped , concrete is not waterproof , i would be willing to bet its just poor air circulation.
 

Bayou Dave

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I am about 3 hours East of you and have the same problem. My carport gets wet from condensation quite often. The way it puddles it is very slippery. I just take a wide broom and spread the water around and hope it finally dries out.
 

Redfred1

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What a difference a day makes! Temp 60; DP 59; H 95 (Rain) Garage floor is dry; checked the plastic; was moist but floor was damp. Could be because of the weather.
I think mick might have the solution. After this weather straightens out some; I"ll run a oscillating fan on low speed overnight.
DRs: we share the pain. I think its worse over there! I have kinfolk in BR; she complains about it ATT. We take trips to Kinder to help your economy.
Will give update.
 

Redfred1

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Today AM: T 72; DP 71; H 97. 4PM T 82; DP 54; H 77. Floor temp was 67. All have been done with a infrared gun. Going to try a oscillating fan.
 

ezbtr

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too funny was just gna post same, here in new house in TX/Hutto my 5 yr old garage does same, it is coated, I'm sure it is a humidity issue, I do have two fans, I can use, one ceiling, one mobile
 

bigdee

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too funny was just gna post same, here in new house in TX/Hutto my 5 yr old garage does same, it is coated, I'm sure it is a humidity issue, I do have two fans, I can use, one ceiling, one mobile

It is a DEW-POINT issue, mostly a southern thing. If your lawn is wet and it hasn't rained that is dew. Easier to control dew point inside a building than humidity. Air movement is first step if that does not work you have to raise floor temperature.
 

bigdee

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Is the garage enclosed? Maybe a dehumidifier or two would help?

Too costly to dehumidify that much volume. Industrial dehumidifiers are expensive and consume lots of power. Plus as soon as you opened an overhead door the humid air would enter. Raising floor temperature above dewpoint is the only solution....this can be done be recirculating the warmer air at ceiling down to the floor. Some cheap ceiling fans could achieve this.
 

Redfred1

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I think mick has the cure I put oscillating on a timer; let it run 2-3 hours. Floor is dry; no dark; damp spots; slab temp around 71. Thanks mick!!!
 
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