Cracked Caulk Fix: The Dry Time That Seals Tubs
Fresh caulk laid over a damp joint traps moisture underneath, so the mold you just scraped out grows right back behind the new bead.
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Friday is Fix-It Friday, and today's repair is the cracked caulk line around your tub. Most people scrape, wipe, and recaulk in one go, then wonder why black spots return within a month. The variable that decides everything is how dry the joint is before the new bead goes in. Caulk can't bond to a damp surface, and any moisture sealed inside becomes a warm, dark home for mold. Give the joint a full 24 hours with the bathroom fan running and the caulk will grip tight and stay flexible. The whole job takes about an hour of hands-on work and costs around $8.
What You'll Need
- 100% silicone tub-and-tile caulk, mildew-resistant, about $6
- Caulk removal tool or plastic scraper, about $4, or a old plastic putty knife you already own
- Rubbing alcohol, for cleaning the joint, a few cents per use
- Painter's tape, for crisp lines, about $4
- Rags or paper towels, free from the junk drawer
- Caulk gun, about $5 if you don't have one
How to Build It
- Cut along both edges of the old caulk with a utility knife or removal tool, then peel and scrape out the whole strip. Leftover bits keep the new bead from bonding.
- Scrub the empty joint with rubbing alcohol on a rag to kill mildew and lift soap film. Rub until the rag comes away clean.
- Dry the joint completely. Wipe it, run the exhaust fan or a small fan for at least 24 hours, and don't use the tub or shower in that time. Press a dry paper towel into the gap, and if it comes out damp, wait longer.
- Tape both sides of the joint, leaving a gap about 1/8 inch wide. Press the tape edges down firmly so caulk can't creep underneath.
- Cut the caulk tube tip at a 45-degree angle, making the opening small, about 1/8 inch. Puncture the inner seal with a nail.
- Apply one steady, continuous bead along the joint, pushing the gun slowly. Moving at a steady pace keeps the line even and fills the gap without air pockets.
- Smooth the bead with a gloved finger dipped in soapy water, then pull the tape off right away at a slight angle. Let it cure per the label, usually 24 hours, before any water touches it.
Fill the tub with water before you caulk, then caulk while it's full and let it cure that way. The tub's weight pulls the joint to its widest point, so the cured caulk stretches slightly instead of cracking when the tub is full and the joint opens up in daily use.
