Why does bathtub caulk keep cracking over and over?
Bathtub caulk repeatedly cracks shortly after application, which traps mildew underneath and forces people to redo the job every few weeks. This endless cycle wastes time and money while failing to maintain a proper waterproof seal around the tub.
What the numbers show
Counted from the threads quoted below. How we count
- People have been saying this in most months since September 2026.
- This comes up 21.5× more often in r/HomeMaintenance than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Using more expensive brandsDid this help you?
- 2Switching to 100% silicone caulkDid this help you?
- 3recaulking frequentlyDid this help you?
- 4filling the tub with water while caulkingDid this help you?
- 5using alcohol to clean the areaDid this help you?
- 6using 100% silicone or stretchy caulkDid this help you?
- 7using a dehumidifierDid this help you?
- 8cleaning with hydrogen peroxide and dawn powerwashDid this help you?
- 9cleaning the surface with alcohol before applying caulkDid this help you?
- 10pushing a toothpick into the gap to test for moisture or spongy materialDid this help you?
- 11putting more caulking over the affected areaDid this help you?
- 12Scraping off the old caulking and replacing it with fresh silicone caulking using a caulk scraper and caulk gunDid this help you?
- 13Scraping it out and redoing the job with 100% silicone sealant, filling the tub with water before caulking so it cures in the shifted position.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“I have recaulked this tub *four times* in the past year or so, and it cracks almost immediately, then grows mildew underneath.”source ↗
“I really don't have time to recaulk every few weeks, and I don't have money to hire someone.”source ↗
“I noticed these small spots where the tile meets the tub, where the caulking (?) seems to be degrading or has been pushed underneath the tile.”source ↗
“I actually noticed this a number of months ago but forgot about it and didn't do anything about it... How concerned should I be about water that has leaked in there?”source ↗
“Bath silicone sealant starting to fail. Is this a relatively easy fix or does it all have to come off?”source ↗
“we cannot seem to get ANY caulking to stick and hold, including silicone, and caulks made specifically for showers/tubs. after 6ish months, it starts to just peel off. we ensure the shower is dry, clean with alcohol first, and it still fails after a period of time.”source ↗
“ugh that pink slime is relentless, i swear it has a personal vendetta against white grout. for the caulking peeling off like that it's usually because the gap between the tile and the tub is too deep, so it can't grip both sides properly. stuff some foam backer rod in there first and then try the silicone again, that should give it something to actually hold onto.”source ↗
“I've sealed my tub with caulk I don't even know how many times now. And it always ends up with the caulk just cracking.”source ↗
“Cleaning the shower today I noticed some caulk was stripping off as I was wiping it. New construction house only moved in about seven months ago.”source ↗
Where this came up
People with this problem also raised
- 7Second-floor bathtub is cracking and flexing with no backup bathroom
- 20Should I put caulk over missing grout in shower corners?
- 9Do I need to caulk my new shower or was it left unfinished?
- 17How to get dark buildup off bathtub caulk
- 2Why is my bathtub overflow leaking behind the wall?
- 7How to fix a botched DIY bathtub finish?