Testing for Moisture before Painting a Garage Floor

What You'll Need
Plastic sheet
Duct tape

When painting a garage floor, you need to make sure that you are not putting paint on top of a concrete surface that has excessive moisture in it. If you paint on top of a concrete floor that holds a lot of moisture, the paint will peel up as the moisture tries to get through. Here are the basics of how to test the floor for moisture before painting.

Step 1 - Tape the Plastic Sheet Down

First, tape the plastic sheet down to the concrete floor. Use a square of plastic about 2 feet by 2 feet. Place the plastic sheet down on the concrete surface and make sure it is spread out evenly. Then, take the duct tape and tape around all of the sides so that it is sealed up.

Step 2 - Wait

Allow the plastic sheet to sit undisturbed. You need to allow it to sit for 72 hours.

Step 3 - Test

Take up the plastic sheet and see if there is any moisture under it. Use a hygrometer to check the moisture level of the floor. If it appears to be wet, you have excess moisture in the slab. The humidity level should be below 80 percent.