How to Seal Cracks in Concrete Slabs Prior to Laying Ceramic Tile

Concrete slabs are commonly used as a foundation for flooring surfaces. It creates a stable subfloor on which a more comfortable and functional material can be laid. Before installing ceramic tile, the cracks in the concrete slab should be properly sealed. This can be accomplished using a polyurethane caulk. It is an adhesive compound that hardens and fills the cracks, creating a more solid foundation for the tiles. The appropriate tools and proper method will enable you to complete the task without professional assistance.

Things You'll Need

• Urethane caulk
• Caulking gun
• Utility knife or scissors
• Foam backer rod
• Spatula or old spoon

Instructions

1. Cut open the tip on a tube of urethane caulk using a utility knife or pair of sharp scissors. Load it into a caulking gun.

2. Apply a bead of the urethane caulk no more than 1/4 inch thick directly into one end of a crack in the concrete. Continue to squeeze the sealant along the entire length of the crack, smoothing the caulk with the tip of the gun as you go.

3. Insert a foam backer rod into cracks larger than 1/4 inch wide. Purchase a rod slightly wider than the targeted gap so it conforms to the space.

4. Push the backer rod firmly into the crack, below the surface of the concrete. Proceed to fill the crack using the caulking gun, with the backer rod as support for the urethane sealant.

5. Prevent direct contact with the caulk by wearing protective gloves. Use a smooth tool such as a spatula or the back of an old spoon to level the urethane caulk with the concrete.

References

• Lowes: Using and Applying Caulk
• Reader's Digest: Caulking Cracked Concrete