Sweaty concrete

turt

Hello everyone,

I'm planning on putting laminate flooring on concrete in one room in my basement. However, when I pulled the current carpet, the pad was moist in some places.

I know that concrete sweats, but, can I tell if I have a serious problem.

Note: the wooden carpet tacks were perfect with no sign of water damage -- so it does not look like water is coming from the foundation.

Thanks.

joecaption

Not all concrete sweatsTape a piece of plastic down on the floor, wait 48 hours, moisture on the back side will tell your there's rising moisture from the slab not having a vaper barrer under it.
Any moisture and no laminite will work.

rusty baker

Or you could do a real mosture test and know for sure.

__________________
"I'm twisted, not sick. Sick implies, I'll get better"
Semi-Retired Installer
Installing since 1973

joecaption

And what's the chance a DIY has a moisture meter laying around?

Bud Cline

Anyone else see any humor in this exchange? Somebody hasn't been paying attention.

rusty baker

Sometimes it is just in a DIYers best interest to do things right.

__________________
"I'm twisted, not sick. Sick implies, I'll get better"
Semi-Retired Installer
Installing since 1973

Maintenance 6

Current technology just doesn't allow us to stare them in the eye or lead them by the hand. The best we can do is type at them and hope they understand.

Daniel Holzman

Concrete does not "sweat". A person or animal sweats, because they expel moisture within their body as part of the cooling mechanism used by many vertebrates.

Concrete conducts moisture from the soil beneath the floor upwards into the room when the vapor pressure in the room is lower than the vapor pressure in the soil. This can happen if the soil is saturated, which can generate high vapor pressure, and the room is conditioned.

The normal fix for this problem is to install a vapor barrier beneath the concrete, such as plastic, bentonite panels, or other waterproof material. If this was not done when the slab was installed, it is expensive to install after the fact. Sounds like it was not done in your case. Installing a vapor barrier above the concrete is theoretically possible, but not likely to be very effective (see multiple threads on DryLok and similar products).

My suggestion is to confirm the moisture issue with the moisture meter, which you can rent. This will tell you the moisture content of the concrete. The moisture meter gage will have a standard range of moisture for dry concrete, which is going to be low, since cured concrete has essentially zero free moisture in it unless it is in contact with a water source, which is probably what is happening in your case.

Assuming the concrete is moist, my suggestion is to forget about the laminate, use only moisture resistant materials, which could include certain paints, and possibly vinyl flooring. Live with the moisture, it is not going away on its own.

rusty baker

Concrete also condenses moisture from the air since it tends to get colder than the surrounding air.

__________________
"I'm twisted, not sick. Sick implies, I'll get better"
Semi-Retired Installer
Installing since 1973