I store cars in my building for friends and family. I moved their cars last night so they can pick them up for the summer and found the under carriages soaking wet, and water all over the floor. This had not occured the last 2 seasons (at least that i could see), as maybe I went on a day this was dry. Not sure. But regardless is there any solutions to prevent this from the happening again?
How to stop cement from sweating in spring?
- Thread starter Fordiesel69
- Start date
The condensation is from the moisture in the air coming into contact with the cold cement. Put a fan in the garage door blowing air in, which will warm the cement faster and keep the air moving which will help prevent the moisture from condensating on the cement.
Humidity and lack of air movement on the cold concrete
Definitely. I'm seeing it on my basement walls as well, the ground is still relatively cold due to our pretty cold winter and now with humid days it's condensing on the walls. The air has been downright juicy lately.
It's a rapid rate of temperature change that does it. When the air temperature rises the absorbed moisture condenses out on the still cold concrete. When the air temperature changes slowly this is much less likely to happen. The only thing that will prevent it is heating or dehumidify the garage.
Condensation happens when a parcel of air is cooled to the dew point of the air. Concrete does hold some moisture, but warmer air coming into contact with the concrete will cool the air and warm the concrete, but the concrete warms much slower than the air cools. Warmer air would not cause the moisture in the concrete to somehow condensate, it would cause the moisture in the concrete to evaporate. The condensation moisture on the concrete comes from the air cooling at the surface of the concrete.
Cool concrete.
Warm moist air.
The moist air cools and slows very near the concrete surface and appears visible as liquid water on surface of concrete.
Need more air movement and warming of concrete. It happens here with rapid warming wet cycles.
Warm moist air.
The moist air cools and slows very near the concrete surface and appears visible as liquid water on surface of concrete.
Need more air movement and warming of concrete. It happens here with rapid warming wet cycles.
I don't believe it's the moisture in the concrete, it's moisture condensing out of the air because - "warmer air coming into contact with the concrete will cool the air and warm the concrete, but the concrete warms very much slower than the air cools"
I get this in my own garage with a painted and sealed concrete floor and also on ceramic floor tiles but it's rare and only happens when there is a rapid increase in air temperature following a cold spell. It takes many days for the concrete temperature to catch up with the air temperature and in the mean time depending on the dew point of the air it will be capable of condensing moisture out of the air.
I get this in my own garage with a painted and sealed concrete floor and also on ceramic floor tiles but it's rare and only happens when there is a rapid increase in air temperature following a cold spell. It takes many days for the concrete temperature to catch up with the air temperature and in the mean time depending on the dew point of the air it will be capable of condensing moisture out of the air.
Long story short... warm air holds more moisture and larger mass holds temperature, so concrete is likley to be cold.
If it is below teh dew point, water condenses on it the same as water condensing on the outside of a glass of ice water.
Take a look at this:
https://www.calculator.net/dew-point-calculator.html
If the air temp in the garage is 80 F and the relative humidity is 50% then if the concrete is at or below 59.7 F (dew point) that happens.
However, if the relative humidity is 65% and at 80F, the dew point is 67.2 F, which is very likely what is going on in your case.
An easy fix is to put a de-humidifier in to drive down the humidity (increases dew point).
If it is below teh dew point, water condenses on it the same as water condensing on the outside of a glass of ice water.
Take a look at this:
https://www.calculator.net/dew-point-calculator.html
If the air temp in the garage is 80 F and the relative humidity is 50% then if the concrete is at or below 59.7 F (dew point) that happens.
However, if the relative humidity is 65% and at 80F, the dew point is 67.2 F, which is very likely what is going on in your case.
An easy fix is to put a de-humidifier in to drive down the humidity (increases dew point).
AZjeff
$50 Site Donor 2023
It would take a pretty big dehumidifier to make a difference in the size of that building. It seems odd that the condensation is just under the cars? Maybe park them over plastic sheets?
I had this problem in my 24x32 garage. I ended up getting a big (home style) dehumidifier and leaving it on 24/7. It's helped a ton.
It also helps trying to keep the garage warmer.
It also helps trying to keep the garage warmer.
I use a dehumidifier in my aircraft hangar for this very reason. Prevents condensation of moisture on all the cold surfaces, including the airplane.
Kestas
Staff member
The warm humid days in Michigan winter result in everything metal in my garage to condense water. I often get corrosion on my tools.
sweet building by the way.
This bothers me like reporters calling bail bond. You get out of jail on bail. Bond is a way of posting bail.
Anyway, there are two kinds of concrete; cement based concrete and asphalt based concrete. Cement based concrete is the stuff almost all garage floors are made with. Asphalt based concrete is the stuff most roads are paved with.
End of picky rant.
Anyway, there are two kinds of concrete; cement based concrete and asphalt based concrete. Cement based concrete is the stuff almost all garage floors are made with. Asphalt based concrete is the stuff most roads are paved with.
End of picky rant.
Fixed it for you.
I try to run some sort of heat source through the winter. Last few winters were a kerosene wick heater but this winter I ran a diesel heater .
Actually, a dehumidifier does create heat. When we were first married and living in a small bottom floor apartment where there was a slab of concrete under the carpet, we heated the whole space with a dehumidifier. All those watts of energy that a dehumidifier consumes have to go somewhere.
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I once had a small storage building with a cement floor and was not seald well at all. Was in a high moisture almost swamp area in Coastal Carolina and was not a good mix. I knew I had a problem when I walked to the building one morning and all the chrome on my Harley looked like a mirror in a bathroom during a shower!
The fix? a vapor barrier between the floor and my bike!
I have moved, still at the coast but I now have a normal garage but to this day, ALL my Harley bikes get parked on some kinda rubber backed mat. Keeps the moisture off the bike and protects the floor from oil or golf cart battery acid etc.
A commercial building rubber on bottom carpet on top entrance mat works PERFECT ( Amazon $50 +/- ) for my motorcycles and golf carts.
I never needed one for my car but have seen mats that may work? A roll of under house plastic would work IMO If the cars are not moved much. I also love my Amazon breathable $40 stretch tight fitting almost thin enough to see through cover. Keep ALL the dust off my bike but lets air flow EZ around the bike in the garage. You can see my rubber mats in the pic.
The fix? a vapor barrier between the floor and my bike!
I have moved, still at the coast but I now have a normal garage but to this day, ALL my Harley bikes get parked on some kinda rubber backed mat. Keeps the moisture off the bike and protects the floor from oil or golf cart battery acid etc.
A commercial building rubber on bottom carpet on top entrance mat works PERFECT ( Amazon $50 +/- ) for my motorcycles and golf carts.
I never needed one for my car but have seen mats that may work? A roll of under house plastic would work IMO If the cars are not moved much. I also love my Amazon breathable $40 stretch tight fitting almost thin enough to see through cover. Keep ALL the dust off my bike but lets air flow EZ around the bike in the garage. You can see my rubber mats in the pic.
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Just part of having a concrete floor. Nice Job on the concrete pour for that size slab. My garage is pretty big and I decided that with no experience at all I could call a few buddies and do my own pour. I ended up with a few cracks and some low spots. But it's just a garage so no big deal. Looking back at it I'm glad I paid people to build the rest of the building.
