How to Fill the Gap Between the Bathtub & Flooring

Kevin McDermott

When you build or remodel your bathroom, you'll need to leave a small space between the flooring and the tub (regardless of what kind of floor it is) to allow for small movements in the building materials over time. That space can create all kinds of problems if moisture from the tub gets down into it, including mold and damage to the subfloor. Sealing off that gap takes minutes.

  1. Mix bleach and water in a 1 to 3 ratio in a spray bottle. Spray down the gap between the tub and the flooring. Let it dry for an hour.

  2. Place a tube of caulk into your caulk gun. Use your utility knife to cut a diagonal hole in the end of the tube, about ¼ inch in diameter, or wider if the gap you want to seal is a little wider than that.

  3. Push a framing nail into the hole to break the internal seal and release the caulk.

  4. Compress the caulk gun trigger until the caulk rises out of the tip of the tube. Hit the release latch at the back end of the caulk gun to stop the flow of caulk.

  5. Set the tip of the tube onto one end of the gap between the tub and the flooring. Compress the trigger until the caulk starts flowing again.

  6. Slowly draw the gun backward along the gap as the caulk comes out so you're laying a smooth, even bead of it. The caulk should completely cover and seal the space between the tub and the flooring. Press the tip of the gun firmly enough that the bead is slightly flattened as it comes out and is sitting fully in the gap.

  7. Hit the release latch at the back of the gun when you get to the end of the gap, and lift the gun. Let the caulk line set for 24 hours.