# Bathtub caulking keeps cracking **URL:** \ **Category:** Factual Questions\ **Created:** [May 4, 2011, 10:28pm UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763 "2011-05-04T22:28:18Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [May 4, 2011, 10:28pm UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/1 "2011-05-04T22:28:18Z")
My apartment bathroom has an ongoing issue: the caulking where the tub meets up to the tiles keeps cracking. The bottom of the tub is pretty flexible and the gap in the crack gets noticable bigger when you step in and walk around. Now I have reported this three times and each time it has ended up cracking again (of course they just keep putting fresh caulk over the old stuff). It seems they’re giving up, saying the caulking is “only cosmetic” and that it’s just something that happens. Personally, I’m concerned about the mildew/mold that grows in the crack and potential long-term damage from water constantly seeping within the crack and getting behind there. So how legitimate are my concerns and any ideas for fixing it? I say the tub must be caulked when it’s full of water and weighted down so that the caulk is normally under compression and won’t be put into tension if someone gets in the tub and weighs it down. I think ultimately I’m going to have go fix this myself if I want it done right. ---
**Author:** ![MobiusStripes](https://avatars.discourse-cdn.com/v4/letter/m/d6d6ee/32.png) [@MobiusStripes](https://boards.straightdope.com/u/MobiusStripes)\ **Post date:** [May 4, 2011, 11:22pm UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/2 "2011-05-04T23:22:10Z")
What kind of caulk? The silicon stuff is pretty flexible. I like the idea of applying it while the gap is large so that it’ll compress. Still, it’ll only cover a gap so large before failing. The rest based on my research when redoing my own bathtub/surround: In theory there should be a vapor barrier (tar paper or plastic) behind the shower surround that overlaps the flange on the tub. Or maybe that’s only if you do tile for the surround. I assume you have a fiberglass tub with a separate fiberglass surround? I know what you mean about gunk getting under there. I lived in an apartment once that had that issue. ---
**Author:** ![SeaDragonTattoo](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeaDragonTattoo](https://boards.straightdope.com/u/SeaDragonTattoo)\ **Post date:** [May 5, 2011, 12:12am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/3 "2011-05-05T00:12:51Z")
Short answer is that it’s a rental. It’s really not your problem. If you’ve notified them, you’ve done due diligence, it’s up to them to upkeep their property properly or improperly as they see fit. If you’re worried about a mold health hazard for yourself, put it that way to them and escalate if needed. If you’re not worried about a health issue for yourself, let it go. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [May 5, 2011, 12:19am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/4 "2011-05-05T00:19:11Z")
put silicone caulk in when you have a couple people standing in the tub. ---
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [May 5, 2011, 1:46am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/5 "2011-05-05T01:46:46Z")
> [@MobiusStripes](#): > > I assume you have a fiberglass tub with a separate fiberglass surround? I know what you mean about gunk getting under there. I lived in an apartment once that had that issue. It’s a fiberglass tub but the surround is made of the standard white, square ceramic tiles. Still, I’m assuming it still has the vapor barrier? > [@johnpost](#): > > put silicone caulk in when you have a couple people standing in the tub. I’ve done this, but it just squeezes out once someone gets out of the tub. The trick is keeping the tub weighed down until the caulk is completely dry apparently. > [@SeaDragonTattoo](#): > > Short answer is that it’s a rental. It’s really not your problem. If you’ve notified them, you’ve done due diligence, it’s up to them to upkeep their property properly or improperly as they see fit. If you’re worried about a mold health hazard for yourself, put it that way to them and escalate if needed. If you’re not worried about a health issue for yourself, let it go. Yeah, it’s just frustrating. These are relatively new apartments (built in '08) that are pretty nice and this is the only issue I’ve had. It looks like I’ll probably end up doing it myself since I’m more annoyed with the mildew that builds up in than concerned health-wise. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [May 5, 2011, 2:01am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/6 "2011-05-05T02:01:20Z")
> [@johnpost](#): > > put silicone caulk in when you have a couple people standing in the tub. > [@BrandonR](#): > > I’ve done this, but it just squeezes out once someone gets out of the tub. The trick is keeping the tub weighed down until the caulk is completely dry apparently. get a bunch of people that really like each other and throw a tub party. ---
**Author:** ![IvoryTowerDenizen](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ivorytowerdenizen/32/17937_2.png) [@IvoryTowerDenizen](https://boards.straightdope.com/u/IvoryTowerDenizen)\ **Post date:** [May 5, 2011, 2:02am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/7 "2011-05-05T02:02:41Z")
I read somewhere to fill the tub with water first and leave it full until the silicone sets. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [May 5, 2011, 2:09am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/8 "2011-05-05T02:09:07Z")
> [@BrandonR](#): > > I’ve done this, but it just squeezes out once someone gets out of the tub. The trick is keeping the tub weighed down until the caulk is completely dry apparently. So fill it with water, lead weights, dead bodies, whatever – something you can leave in place until the silicone sets. On preview, what he said – but I like the range of options I mentioned. 😃 ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [May 5, 2011, 2:39am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/9 "2011-05-05T02:39:58Z")
The real problem is that the tub itself is not sufficiently supported underneath, thus if flexes when occupied, so that movement inevitably makes the caulk crack. Replacing the caulk is a cosmetic fix. Replacing the caulk with a more flexible caulk, like silicone, is a better cosmetic fix. A real fix would involve removing the tub, providing better underfloor support, and then reinstalling the tub. Very expensive. A landlord isn’t going to spend that, when they can just replace the caulk every year or so. So you just have to live with it as long as you live there. If it bothers you, call them every few months. Washing the area with bleach will reduce the growth of mold or mildew, if that’s bothering you. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [May 5, 2011, 2:45am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/10 "2011-05-05T02:45:48Z")
I have a 60+ year old house with a bit of movement in the tub. I’ve had pretty good luck using the “fill the tub with water” method that has been mentioned a few times already in this thread. If there is enough movement in the tub it’s going to crack again no matter what you do, but filling the tub first before caulking lasts a good while. Since this is a rental you will probably move out before it becomes a problem again. > [@SeaDragonTattoo](#): > > If you’re worried about a mold health hazard for yourself, put it that way to them and escalate if needed. Trying to escalate the issue seems like far more bother than it’s worth, considering the alternative is just a couple of bucks worth of caulk and a bit of your time. That’s just my opinion though. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [May 5, 2011, 11:45am UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/11 "2011-05-05T11:45:20Z")
[QUOTE=BrandonR] I’ve done this, but it just squeezes out once someone gets out of the tub. The trick is keeping the tub weighed down until the caulk is completely dry apparently. [/QUOTE] The best you’ll be able to do without gutting the thing out and re-installing the tub with proper structure underneath is to clean out the old caulk, then fill the tub with water, caulk the joint, then leave the water in the tub until the caulk has cured. It’s one thing for a fiberglass tub to flex when you get in or out, but if it’s actually moving like you describe, it’s going to be someone’s headache later on. With that much motion either the tub itself or more likely the drain pipes are going to eventually crack and it will start raining downstairs. Just be glad you only rent the place. ---
**Author:** ![Max\_Torque](https://avatars.discourse-cdn.com/v4/letter/m/e9bcb4/32.png) [@Max\_Torque](https://boards.straightdope.com/u/Max_Torque)\ **Post date:** [May 5, 2011, 2:31pm UTC](https://boards.straightdope.com/t/bathtub-caulking-keeps-cracking/580763/12 "2011-05-05T14:31:50Z")
Another note, if you’re going to do this yourself: in general, caulk doesn’t stick to caulk. To get a good, lasting seal, you need to get rid of the old stuff. Scrape it off, dig it out, clean it up, so you have a nice clean surface to work on before you apply the new stuff. They make a tool to get caulk out of deep cracks. I think it’s called a “caulk-sucker”. (okay, the last line was a joke, but not the rest of it)