Short answer
Cut out every bit of the old caulk with a utility knife or caulk remover, then clean the joint with rubbing alcohol and let it dry completely. Tape both edges, fill the tub with water, and run one steady bead of 100% silicone labeled for kitchen and bath. Smooth it with a wet finger, pull the tape right away, and wait 24 hours before the first shower.
How to re-caulk a bathtub
1Cracked caulk lets water in
Gaps, cracks or caulk peeling off the tub mean water is getting behind the tile. New caulk will not stick to the old, so it has to come out.
Read all the steps
- Cracked caulk lets water in. Gaps, cracks or caulk peeling off the tub mean water is getting behind the tile. New caulk will not stick to the old, so it has to come out.
- Cut out all the old caulk. Run a utility knife or a caulk remover along both edges and pull the strip out. Scrape off the last bits until the joint is bare.
- Clean, dry and tape both edges. Wipe the joint with rubbing alcohol and let it dry fully. Put painter's tape on the wall and on the tub, leaving a thin gap for the caulk.
- Fill the tub, then run one bead. The weight of the water opens the joint like a full bath. Cut the tip small and at an angle, and run one steady bead of 100% silicone.
- Smooth it and pull the tape. Run a wet finger along the bead once. Pull the tape right away, while the caulk is still wet, pulling it away from the joint.
- Wait 24 hours before showering. Most silicone needs about 24 hours to cure. Leave the water in the tub until then, and check the tube for its own time.
- Still not fixed? Call a handyman Especially if: the wall feels soft or tiles move when you press them.
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Why the caulk fails
Caulk stretches every time the tub fills and empties, and the bathroom goes from steamy to dry every day. After a few years it hardens, cracks and pulls away. Black spots under clear caulk are mold on the caulk that got behind it. If the tub flexes when you step in, the joint keeps tearing until the tub is braced.
What not to do
- Do not caulk over old caulk. New silicone does not bond to it and peels off within weeks.
- Do not use plain acrylic or painter's caulk in a wet area. Look for 100% silicone labeled for kitchen and bath, with mildew resistance.
- Do not caulk a damp joint. Trapped moisture is how mold starts under a new bead.
- Do not grout the joint between the tub and the wall. That corner moves, so it needs caulk.
If old silicone will not come off
A thin film of old silicone keeps new caulk from sticking. Scrape it with a plastic razor blade, then rub it with a silicone caulk remover or rubbing alcohol on a rag. Rinse, dry, and only then tape and caulk.
When to call a handyman
- The wall feels soft or tiles move when you press them.
- There is a stain or a drip on the ceiling below the bathroom.
- The new caulk cracks again within a few weeks because the tub flexes.
- Black mold keeps coming back under fresh caulk.
Frequently asked questions
Can I put new caulk over old caulk?
No. New silicone does not bond to old caulk, so it peels off within weeks. Cut out the old bead, clean the joint and let it dry first.
What is the best caulk for a bathtub?
100% silicone labeled for kitchen and bath, with mildew resistance. It stays flexible and stands up to water better than acrylic caulk. Pick a color that matches your tub or grout.
How long after caulking can I shower?
Most silicone needs about 24 hours to cure before it gets wet. Some fast-cure products say less, so check the tube. Showering too soon can wash out or wrinkle the bead.
Should I fill the tub with water before caulking?
Yes. The weight of the water lowers the tub a little, like when someone is in it. Caulk it that way and the joint will not tear the first time you take a bath. Drain it once the caulk has cured.
How do I get old silicone caulk off?
Cut along both edges with a utility knife or a caulk remover and pull the strip out. Scrape the leftovers with a plastic razor blade, then wipe with rubbing alcohol or a silicone remover.
How often should you re-caulk a tub?
Whenever you see cracks, gaps, peeling or mold under the bead, usually every few years. Check it once a year. Small gaps let water behind the tile, and that repair is much bigger.