Since concrete is so porous, it can also absorb and transfer ground moisture.
Floor covering manufacturers will also list the allowable concrete moisture content on which their products can be installed.
Moisture can be a problem when a floor that looks dry really isn’t.
The Spruce / Sanja Kostic
If given ample space, warmth, and ventilation, water vapor will simply evaporate.
But when flooring is laid directly on the concrete, it effectively creates a watertight and airtight barrier.
Moisture builds up and has nowhere to go.
The Spruce / Sanja Kostic
verify the plastic has no holes or tears.
Secure the Plastic
Spread each plastic square out flat over a dry area of concrete.
Tape along all four edges of the square with duct tape or other waterproof tape.
The Spruce / Sanja Kostic
Firmly press the tape to create a moisture-tight seal with the plastic and concrete.
Use as many squares as needed to test all the main areas that may get flooring.
Tip
confirm that the concrete where you place the plastic is dry.
The Spruce / Sanja Kostic
If it is damp or even darkened by moisture, it will skew your test results.
Examine the Plastic
Wait at least 48 hours, then inspect each plastic square.
First, check the top surface of the plastic to see if any moisture has beaded up on it.
The Spruce / Sanja Kostic
This is an indication of excess moisture in the air.
Next, peel up the plastic and feel its underside.
This will give you a sense of what it will take to keep the floor dry.
The Spruce / Sanja Kostic
This can help you choose a flooring material that can tolerate the measured level of moisture.
The sleeper system is usually placed atop a vapor barrier such as 6-mil plastic.
Another is to cover the concrete with subfloor panels, such as DRICORE.
The Spruce / Sanja Kostic
These are common techniques used under carpeted basement floors.
The manufacturer’s literature will specify installation requirements to satisfy the flooring’s warranty.
However, the amount of moisture present in the concrete may or may not cause issues.
Watch for salt residue on the floor from condensation.
It’s always a possibility that a slab home will have moisture problems in the concrete flooring.
Moist concrete that is not mitigated can contribute to mold and other problems in a slab home.
