A concrete shower floor should be sealed and free of moisture before it is painted. Evidence of moisture, such as water beads or damp surfaces, will make it difficult to paint the floor. This issue needs to be addressed prior to any prep work or painting takes place.
Painting a concrete shower floor can involve a floor that has recently been poured or an existing floor that had previously been painted. For a new concrete shower floor, be sure to wait until the concrete has cured before testing for moisture and painting the floor.
Step 1 - Remove Moisture
To test for moisture in the concrete, lay a piece of plastic and let it sit for a couple of days. What will take place is that any moisture that is in the concrete will bubble up and appears as a film on the plastic sheet. If any moisture appears, you will have to dry the concrete out and retest before applying the paint and sealant.
Use large area fans and a dehumidifier in the area to remove moisture from the concrete. This may take some time depending on how much moisture is in the concrete floor.
Step 2 - Prepare the Concrete Floor
Once the moisture has been removed from the concrete floor and tested, you can begin prepping the floor to be painted. If the floor has been painted in the past, remove any loose paint and other dirt and debris using a shop vacuum.
Patch any holes in the concrete using a concrete patch. Use an etching compound to prepare the floor to accept paint. As soon as the etching compound dries, vacuum the floor again and apply the paint. The painting should be followed by a sealer, which completes the job.