new garage floor is sweating

[glassman]

What causes the new concrete floor to sweat. It is a pole barn construction that is 60 plus years old and the floor is 3 months old. I have never seen a floor sweat this bad. How do I stop it?

 

[ws27]

My guess is that you are going through the same air mass we are here in Mass. Your floor is cold from all the previous cold weather and now a warm moist air mass has moved in and you are experiencing a condensing episode like a glass of ice water in the summer. Right now I'm keeping my garage tight as possible as not to let in the moisture. You'd be amazed how much water is contained in warm wir.

Too late to stop it now, unless you can dehumidify the existing air and not let in anything more. As soon as the cold dry air comes back it will go away.

 

[RustyRatRod]

Wait till the weather warms up and seal it.

 

[glassman]

Thanks guys. Weather is changing at a moments notice and I would say you have hit it on the head.

 

[snakeoil24]

You can seal it now, if you use urethane Moisture cured sealer. it loves the floor sweat. But they should have put a moisture barrier under the slab.

 

[Budnicks]

You can seal it now, if you use urethane Moisture cured sealer. it loves the floor sweat. But they should have put a moisture barrier under the slab.

bingo, could probably more likely be the issue, moisture coming up thru the ground... did they use plastic or black moisture barrier under the gravel & rebar/wire, before they poured the concrete slab ??

 

[hunt2elk]

I bet there was no vapor barrier put under the cement. About all you can do now i seal it like mentioned above. I put 2 inch styrofoam and a vapor barrier under my cement when building my shop. Havent had any problems with sweating.

 

[747mopar]

I've had the same problem, anytime it goes from cold to warm everything in the garage sweats if the doors are open. I keep everything closed up tight and don't have near the issues plus I keep a dehumidifier in the paint booth with the car.

 

[Meep-Meep]

I was thinking it's working too hard trying to hold up all the stuff you have in there. How did I do Rusty?

In all seriousness a lot of good info on this thread. A cold surface is a pump in the high vacuum world and that means gases (water vapor) will condense.

 

[glassman]

What causes the new concrete floor to sweat. It is a pole barn construction that is 60 plus years old and the floor is 3 months old. I have never seen a floor sweat this bad. How do I stop it?

This is a 2 year old thread that I started and again I have a new slab of concrete, 30x42. First slab was 40x42 with no plastic , but this new slab has the plastic between the gravel and the concrete. I will keep you informed on any sweating issues. So far, none

 

[dvw]

What causes the new concrete floor to sweat. It is a pole barn construction that is 60 plus years old and the floor is 3 months old. I have never seen a floor sweat this bad. How do I stop it?

Mine has plastic and still sweats some days in the summer. I used to use a dehumidfier but it got pretty warm on hot days. Now I installed old window style AC unit. Works excellent even cooling 960 sq ft.
Doug

 

[eldubb440]

mine sweats like a mo fo when conditions are just right....... cold floor, warm moist air.......... i dont see how plastic under the floor would stop that.......... puitting in a/c when i can

 

[Richard Cranium]

If it's been cold inside inside the garage for a long period of time and you throw open the doors on a warm day, the floor is going to sweat no matter if there's a moisture barrier or not.

 

[Cranky]

Yup, RC is right. Keep the dang doors closed!! A vapor barrier helps but it's not a cure all. I'm in the south and when it's been cold over night then warms up the next morning, mine will sweat too if I open up the doors and leave them open. My shop has insulated walls but the roof isn't but that helps keep the place pretty cool inside until around 1pm if the day is warm and the sun is shining.

 

[monaco66coupe]

Whenever cement is poured, the need for temperature control follows. When I do pour I will heat the space. Cement is a sponge,and sucks moisture out of the ground. I stored all my cars in an airplane hangar for 17 years, and the cement pads in the center of the hangar were for the landing gear and fuselage. the rest of the area was rock. Anything on the cement rusted badly, and was damp all the time. Whatever was on the rock did nothing. The cars stayed perfect. I see it in new houses all the time, until the house gets the furnace.Vapor barriers help, but if your ground tends to be saturated, a lot of circulation is needed. all the time.

 

[ws27]

If it's been cold inside inside the garage for a long period of time and you throw open the doors on a warm day, the floor is going to sweat no matter if there's a moisture barrier or not.

That and all the other things inside including bare (and now rusty) metal.

 

[rakort]

Yeah, its basic physics. A cold slab, regardless of moisture barrier or not, will condense moisture out of the air. Its a matter of the dew point of the air and the temperature of the slab. It drives me crazy! I hate it! Now that said. Keep your slab warm (in floor heat? heat above the slab? insulation under the the slab?) or lower the dew point/relative humidity above the slab with AC or raise the temperature (and dew point) above the slab. So all we need is climate controlled garages. Simple!