How to Seal a Bathtub with Silicone Caulk

Water is the silent enemy of your bathroom. When the caulk around your bathtub begins to crack, peel, or turn black with mildew, it isn't just an eyesore—it is a direct invitation for moisture to seep into your wall studs and subfloor. A job done well results in a clean, crisp line that flexes with the tub's movement without pulling away or harboring mold growth. Applying caulk is less about artistry and more about preparation and steady pressure. If you rush the removal or leave behind soap scum, the new silicone will fail within months. Treat the prep work as the main event, and the actual application of the sealant becomes a simple, satisfying victory lap.

1. Scrape to Bare Substrate. Use a sharp plastic or metal caulk removal tool to scrape away every trace of the existing sealant. Ensure the gap is completely clear of debris and old residue down to the bare tub and wall surface.
2. Sanitize Every Trace. Wipe the entire joint with a rag soaked in high-percentage isopropyl alcohol. This removes all soap scum, oils, and microscopic mold spores that would prevent the new caulk from bonding.
3. Frame Perfect Edges. Place strips of painter's tape on the tub and the wall, leaving only a small, consistent gap where the caulk will go. This ensures your final bead has perfectly sharp, straight edges.
4. Angle the Cut Right. Cut the tip of the caulk tube at a 45-degree angle. Ensure the hole is only slightly smaller than the width of the gap you are filling to maintain control over the bead size.
5. One Smooth, Steady Pass. Using a steady hand, apply a continuous, even bead of silicone into the gap. Keep the caulk gun at a consistent angle and move at a steady pace to avoid gaps or over-application.
6. Smooth, Then Strip Tape. Run a gloved finger or a specialized smoothing tool over the caulk once to press it into the gap. Immediately peel away the painter's tape at a 45-degree angle before the caulk begins to skin over.