How to Seal a Concrete Slab

Seal concrete slabs to prevent excessive moisture from seeping into the surface.

Concrete slabs are sealed after they have been poured and had a chance to properly cure. Sealing a concrete slab keeps excess moisture from penetrating deep into the pores of the concrete. This layer of seal also helps to prevent spills and stains from seeping into the concrete, which would make a concrete surface that is hard to keep clean. To create a permanent barrier against moisture and spills, apply a non-breathable, penetrating concrete sealant.

Things You'll Need

• 5-gallon bucket
• Concrete degreaser
• Long-handled scrub brush
• Pressure washer
• Box fans
• Gloves
• Safety goggles
• Non-breathable penetrating concrete sealer
• Paint tray
• Long-handled paint roller
• Small paintbrush

Instructions

1. Fill a 5-gallon bucket with warm water. Add the concrete degreaser cleaner into the warm water according to the package instructions.

2. Wash the concrete slab with a long-handled scrub brush to remove dirt, loose debris and grease. Rinse the concrete with a pressure washer to clean the surface of all concrete degreaser residue.

3. Allow the concrete to dry, which could take up to 48 hours. This is best done in the warm summer months so the concrete will have a shortened drying time. To help accelerate the drying time of the concrete slab, place several box fans around the perimeter so they blow over the surface.

4. Fill a paint tray with non-breathable, penetrating concrete sealer. Cover a long-handled paint roller with the concrete sealer, and apply an even coating over the entire concrete surface.

5. Cover small areas on the concrete, such as edges and corners, with a small paintbrush. Allow the concrete sealer to dry according to the package instructions.

6. Apply a second coat of penetrating concrete sealer with the long-handled paint roller, as instructed by the manufacturer. Some brands of sealer recommend applying the second or third coat before the first coat has a chance to fully dry.

7. Allow the concrete sealer coats to dry before using the concrete slab.

Tips & Warnings

• Allow new concrete to cure completely for at least 30 days after installation before applying a coat of sealer.

• Wear gloves and safety goggles when applying the concrete sealer to protect yourself from harmful chemicals that may splatter onto your skin or face.

• Read the instructions on the package of the concrete sealer beforehand to reduce the chance of mistakes.

• Wait until temperatures are steadily above 50 degrees Fahrenheit before applying the sealer onto the concrete.

References

• Ask the Builder: Concrete Sealants