How to Re-Caulk a Bathtub (No More Moldy Caulk)

What you'll need

• 100% silicone caulk, kitchen/bath formula with mildew resistance ($8–$12)
• Caulk gun ($6–$10, or borrow one)
• Utility knife or caulk removal tool
• Caulk remover gel (optional but helpful, ~$8)
• Bleach or mold-killing cleaner
• Rubbing alcohol
• Painter's tape
• Paper towels and rags

Step-by-step

1. Cut out all the old caulk. Score along both edges of the old bead with a utility knife, then pull it away in strips. Get aggressive here — any old caulk left behind is a bond failure waiting to happen. A plastic caulk removal tool helps in the corners.
2. Dissolve the residue. Apply caulk remover gel to stubborn bits, wait per the instructions, and scrape clean. Silicone leaves an invisible film that new caulk won't stick to, so this step matters more than it looks.
3. Kill the mold underneath. Scrub the joint with a bleach solution (1 part bleach to 10 parts water), let it sit 10 minutes, and rinse. If the drywall or grout behind the caulk is black and soft, stop — that's rot, and it needs a pro before re-caulking.
4. Dry it completely. Wipe the joint with rubbing alcohol — it displaces moisture and evaporates fast. Then wait. The joint must be bone dry or the silicone won't cure properly. An hour of air-drying after the alcohol wipe is a safe bet.
5. Tape both sides. Run painter's tape along the tub edge and the wall, leaving about a 1/4-inch gap where the caulk bead will go. This is what separates a pro-looking job from a smeary mess.
6. Cut the tip and lay the bead. Cut the caulk tube tip at 45 degrees, opening about the width of the joint. Hold the gun at 45 degrees and push (don't pull) a steady bead along the joint in one continuous motion.
7. Tool the bead smooth. Wet your finger with soapy water and run it along the bead in one smooth pass to press it into the joint. Then immediately peel the tape away at an angle while the caulk is still wet.
8. Let it cure 24 hours. No showers, no splashing. Silicone skins over in 30 minutes but needs a full day to cure through. Tape a "do not use" note on the shower handle if you share the bathroom.

<div class="safety"> <strong>🛑 Stop and call a pro if:</strong> <ul> <li>The wall or drywall behind the old caulk is soft, crumbly, or black with rot — water has been getting in and the damage goes deeper than caulk.</li> <li>The tub itself is cracked, or the tub moves when you step in it — that's a structural or plumbing issue.</li> <li>You find mold spreading across a large area of wall, not just the caulk line — that needs proper remediation.</li> <li>The gap between tub and wall is wider than half an inch — caulk alone can't bridge it; it needs backer rod or a different fix.</li> </ul> </div>

DIY vs pro cost

Printable checklist

• [ ] Cut out ALL old caulk — no shortcuts
• [ ] Dissolve silicone residue with remover gel
• [ ] Scrub joint with bleach solution, rinse
• [ ] Dry fully; wipe with rubbing alcohol
• [ ] Apply painter's tape both sides of joint
• [ ] Lay steady 45° bead in one pass
• [ ] Tool smooth, peel tape while wet
• [ ] Keep dry 24 hours — no showers

Related guides

• How to Remove Mold from Bathroom (Tiles, Grout, Caulk)
• How to Remove Candle Wax from Carpet and Fabric
• How to Descale a Kettle (Hard Water Areas)