Wet concrete, what am I missing???

[383 240z]

I've been doing a bunch of work to my shop taking care of a bunch of it's short comings. New roof, new windows, grading ect. All of these were in an effort to dry up the shop. I didn't put a water barrier under the concrete slab. It was poured before I found this website and my concrete guy did not say anything about it.

So today I go out side and my floor is getting damp. I should say that it has been raining since early this morning. As I am out in the shop working it's getting wetter and wetter. I did notice that when I moved a few small boxes that there was a perfect square of dry concrete under them. That makes me think the water is coming from the air and condensing ON the slab, rather than coming up THRU the slab.

If it's weeping up thru the slab am I sunk? If it's coming from the air, what can I do? Just buy some big de-humidifiers and let them run non-stop? I've got a 3' drum fan running now trying to dry it up. The machine shop has a wood floor, but I'm afraid that the air is still holding lots of water and will start to rust all the nice new machine tools and work holding tools I've been buying all summer. Keith

 

[skulldrinker]

I dont have plastic down either. Mine stays dry. I guess because I have a Modine furnace in there and I keep the temp at 45 or above . In the summer I open the attic entrance in the ceiling to allow air flow. My shop is drywalled and tapped.

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[1949 caddyman]

What is the temp of your slab, what is the dew point? If the slab temp is at the dew point wont the water in the air form dew on it? I am not a scientist, just thinking about your problem.

 

[outdoorsman310]

one time the entire shop floor was covered in water from condensation. never happened again but was weird

 

[383 240z]

1949 caddyman. Thats what I am thinking my problem is. However I need to find a way to stop it. Will just keeping the air moving help? I'm thinking about buying 2-3 good de-humidifiers just to try to protect the machines and tooling. Keith

 

[JakeKohl]

If it is condensation, the problem is that the air temperature over the slab warmed considerably faster than the slab. Warm moist air over a cold dry slab will condense water vapor (like a glass of ice water on a hot day). Moving air will not really help (might make it worse). The problem will extend to anything in the garage with considerable thermal mass (heavy metal tools, etc.). Stabilizing the indoor temperature so that it doesn't swing wildly is the best fix (insulation, HVAC, and/or leaving the door closed).

 

[JimVonBaden]

If it is condensation, the problem is that the air temperature over the slab warmed considerably faster than the slab. Warm moist air over a cold dry slab will condense water vapor (like a glass of ice water on a hot day). Moving air will not really help (might make it worse). The problem will extend to anything in the garage with considerable thermal mass (heavy metal tools, etc.). Stabilizing the indoor temperature so that it doesn't swing wildly is the best fix (insulation, HVAC, and/or leaving the door closed).

Really?

Jim

 

[Dale Leeds]

Any concrete floor in any type of area can/will sweat. My basement floor sweats. My garage floor sweats. I wouldn't worry about it. It won't damage anything being damp. And it will soon dry out.

 

[383 240z]

This is more than a "little" sweat. It completely covers the floor, I was wiping it up with rags and a mop. I'm concerned as that water has to go somewhere and I'm really worried it will deposit on my mill before I get it moved into the small shop. I'm really worried I'm going to loose some of the stuff in the shop to rust. Keith

 

[Hornman]

Your floor is sweating because it is colder than the air. Your "dry floor under the box" experience proves that the water is coming from the air, not up through the the slab. If you keep the floor temp above the dew point temp there will be no water on the floor. Since you are in Pittsburg, I'm assuming you have a shop heater. Sounds like it is time to fire it up.

 

[Dan_inthewind]

I have the same problem depending of the time of year. Mine actually is worse in the summer hot days.

Garage is heated so no sweating once the heat kicks in but on a hot day closed up the floor is cooler and makes the garage a nice place to be. But the more you walk around the more the floor sweats and it gets to the point I use the squeegee to get the water out.

Small ceiling fan and crack the window open a bit and it dries up.

 

[KPSquared]

Radiant tube heater. Keep the slab warm. Just a thought?

 

[FMC]

concrete floors are sponges for air borne water and release it back to the air under the right circumstance, if the floor isn't sealed that might be a good starting place, dehumidifiers are great but make sure it has a low freeze point, the cheap units freeze up real easy

 

[383 240z]

I guess I could re-seal the concrete, It was done a few years ago, it could be due for another coat. I would love to heat the garage, however that will be cost prohibitive for awhile. There is no natural gas in my area, that leaves wood, coal, and oil. I've been insulating as I build the interior walls. Should have a finished ceiling by this time next year. If this is just a humidity thing, I will put up a ceiling fan or 2, I moved a de-humidifier out there, no need to run it now, it's low 20's and dry for the forseeable future.

I draped canvas drop cloths over the mill and the tooling, my thoughts are that any dew will stay on them, not the tools. Keith

 

[bullnerd]

My old garage just went though this today and yesterday, with the big temp swing. Everything is soaked. My mill looks terrible!

 

[FMC]

you could get Dow Flake/ calcium chloride and keep some inside your machine wraps it will dry up air moisture in confined spaces