How to Seal a Basement Floor

A concrete basement floor is the most likely place in the home for unwanted moisture to seep. This moisture can not only cause mold and bacteria, but it can also ruin stored goods. One of the best ways to prevent this seeping water is to seal the unfinished floors. Although not difficult, it’s important to acquire a good seal through proper technique. Here are five steps to help you through the process.

Step 1 - Clean and Test Floors for Moisture

You may decide to paint your unfinished basement floor and are wondering whether you will need to also seal it. There is a simple way to tell if your floor needs to be sealed before you paint it.

Use strips of duct tape to attach a plastic bag to your concrete floor. Be sure the edges of the bag are completely sealed to the concrete and that they do not allow any moisture under the bag to escape through unsealed edges. Leave the sealed bag on the floor overnight. If you see moisture on the floor the following morning when you remove the bag, seal the floor before painting.

Step 2 - Patch and Fill Cracks and Holes

Like any good seal job, the end result is greatly influenced by the surface preparation. Take the time to fill small holes with concrete patching compound. If you find holes or cracks that are too large to fill with the patching compound, use wet concrete or mesh to fill them. When the concrete has cured, spread the patching compound over the new concrete and let it dry overnight.

Step 3 - Apply the Sealer

When the floor is prepped and dry, it’s time to apply the sealer. Using a large paintbrush, apply the sealer in corners between the walls and floor where you will not likely be able to apply it with a roller. Using a lint-free roller, apply the sealer to the entire surface. Continue applying and spreading the sealer until you create a wet and glistening appearance. Let the sealer dry completely.

Step 4 - Apply the Paint

Brush paint into the corners of the room, as you did with the sealer. When you’ve finished with the corners, use a lint-free roller to apply a coat of epoxy paint to your basement floor. Allow the coat to dry. In normal humidity, drying should take 24 hours. In humid climates, it may take up to two days.

When the first coat has dried, apply a second coat of paint. You can apply a third coat if it is needed.

WARNING: Epoxy products are toxic to inhale or touch, so make sure you're wearing safety gear (gloves, long-sleeved clothes, respirator mask, safety goggles) and check that the work area has proper ventilation before you start working.

Step 5 - Add Texture

To add color and a texture to your basement floor, sprinkle latex chips over the floor after the second coat of paint. Complete this step while the paint is still wet.