When there is rain outside, my carport floor sweats bad. It's not that rain is coming in, it just sweats enough to cover the whole floor with a film of moisture.

1. Hard to work in all that water.
2. SLICK AS (*&%#

Has anyone had any sucess with a sealant or something? I know that a vapor barrier during prior to pouring the slab would have been ideal, but I didn't build it.

I'm also afraid that even if I enclose the carport, that this will still be a problem.

Any thoughts?

Thanks
-Matt

Check your drainage around the slab, make sure water off the roof is getting far enough away. Maybe install perf pipe in a bed of gravel around the slab to drain water away. Anything you can do to keep the perimeter of the slab dry will reduce moisture coming up from underneath. Won't do much for condensation though.

I have the same issue in my shop, and you are right, enclosing won't help much, if at all. What is probably happening is that the slab stays cooler that the ambient air, and when the humidity climbs quickly (like when it rains), it condenses on the cooler slab like a cold beer can. It only happens to me when the weather has been cool, then warms slightly. I resolved it by rolling out the old shitty carpet I pulled from the house onto my work area when I am planing to work in the shop and the weather looks like it might come together to make the floor sweat. If the air doesn't contact the floor directly, the moisture can't condense on it. If you have a nearby "Shitty Carpets R Us" store or some other way to get a big hunk of old carpet, give it a shot.

I have had the same experience in Ontario, CA warehouses where swampcoolers are utilized. Wen your humidity increases too much your floor will sweat. The concrete retains its temperature much better than the air around it. Therefore sealents will not prevent this as the will become the temperature of the concrete. The best bet is to remove the moisture from the air or heatingf the concrete. Unfortunately neither of those suggestions are inexpensive.
Old carpet sounds like a good bet temporarily, but the carpets backing will still get the moisture and with out good air movement the carpet will get moldy if it is allowed to stay wet a long time. This is not that big of a deal unless you have alllergies to mold spores.

I never leave the carpet down fo more than few days to a week at the most, for just that reason. But, the only moisture would be from the edges getting wet, as upward percolation through a raised slab is usually minimal, and at my place, doesn't happen at all.

Sounds like the guy that poured the slab didn't put down any plastic under the concrete before they poured it....

I did half of my old shop this way and the floor on that end never sweats. The other half has no plastic and sweats terriably.

How about those interlocking rubber tiles like I've seen at Costco? Maybe they'd act as a barrier for humidity and be more comfortable to lie on too.