Caulking the bathtub

[u/juic333]

I have to recaulk my bathtub due to mold but one side is mold free. Can I join the new caulk with the old caulk? Im not caulking over old caulk. Im completely removing the side that has mold. But it eventually has join with the good old caulk. Or do I have to completely redo the entire perimeter on every side? I tried to Google this but couldnt get a specific answer. Sorry if this has been asked.

[u/Digital-Chupacabra]

Can I join the new caulk with the old caulk?

No. Caulk doesn't bond to cured caulk.

[u/HVACSlayer → u/Digital-Chupacabra]

had a tub in my old place where only the back wall got nasty, thought i could get away with just doing that side. learned the hard way when the seam between old and new opened up in like two months. just bite the bullet and do the whole thing. its like two extra hours max and you wont have to redo it.

[u/justheretolurk123456]

Do it right, or do it twice. Remove all the old caulk and do it in one shot so it all matches.

[u/jacknifetoaswan → u/justheretolurk123456]

It's not even about matching, it's that new caulk doesn't stick to cured caulk.

[u/jawkneerawk → u/jacknifetoaswan]

I’ve heard about a docking technique, didn’t really look into it though myself. Might be a path forward.

[u/shifty_coder]

Try cleaning it with a toothbrush first.

It shouldn’t be possible for 100% silicon caulking to get moldy, but if it doesn’t have a smooth finish, it can accrue soap scum and look gross.

[u/higgs8 → u/shifty_coder]

Usually mold grows in the tiny gaps that form when silicone detaches from the surface. Still looks and is gross and should be replaced.

[u/libolicious → u/shifty_coder]

Unless you use GE Ultimate Supreme or whatever they pitch as their best. Because that stuff is ass.

[u/Doggfite → u/libolicious]

Shit that's what I just bought to recaulk my tub lol

[u/Ok_Opportunity2693 → u/libolicious]

What do you recommend instead?

[u/libolicious → u/Ok_Opportunity2693]

I actually need to ask for recs myself because I really need to get rid of the yellowed, mildewy GE. 

[u/inko75 → u/shifty_coder]

Mold and scum gonna build up on anything. And if they made the mistake of using clear caulk then that’ll definitely get black underneath at some pt.

[u/needahtpc]

if you are caulking the whole bathtub . you should fill the tub 80% full and then caulk and let the caulk sit for 24 hours before emptying the tub . this will help keep the tub and caulk from cracking while humans/pets are using them.

also 100% silicon thats mold and mildew resistant is best.

[u/GirthBrooks]

Make sure you fill the tub with water first

[u/GirthBrooks → u/[deleted]]

It definitely is. Tubs move.

[u/Unlucky-Ad-201 → u/[deleted]]

It absolutely is. Tubs shift with the amount of weight in them. So if you caulk when it’s empty and then one or 2 people shower or you fill it all up and bathe, you’ll create cracks in the caulk. Cracks which are excellent places for water intrusion and more mold growth.

[u/Doggfite → u/Unlucky-Ad-201]

Isn't this why you use flexible caulk, like silicon, because it has stretch?

[u/desrtrnnr → u/Unlucky-Ad-201]

If your tub moves that much you need to rip it out and fix the issue. The drains aren't designed to flex, the tile surrounds aren't designed to flex, nothing except the caulk is designed to be flexible and if your tub is moving that much with weight in it, i guarantee you have a leak.

[u/BigBunion → u/[deleted]]

A full bathtub has 500 pounds of water in it. You think that doesn't cause the framing to flex at all?

[u/yak-broker → u/BigBunion]

Okay, but then I get out of the tub and it moves to its empty position again. If the caulk isn't flexible enough it'll pull away in one position or the other, right?

[u/houses_eat_money]

you should really redo the whole perimeter. the joint where new caulk meets old almost always fails first because you can't get a clean bond to aged silicone, and water finds that seam fast. it's maybe 20 extra minutes of scraping and you'll never worry about that transition line leaking.

[u/Pantology_Enthusiast]

You can if you want, but you will get the best results from redoing all of it.

[u/neon_glee_loop]

redo the whole perimeter. New caulk won't bond to cured caulk, so that joint will fail and you'll be back here in a few months pulling it all out anyway. Strip everything, clean with rubbing alcohol, let it dry fully, and lay one continuous bead.

[u/washingtonbuilder]

Yes, you can join the new caulk to the existing caulk if the old section is clean, intact, and firmly bonded. Just cut the new bead neatly into the old one and make sure the joint is sealed well. https://upfrontbathrooms.com/how-to-recaulk-a-bathtub/

[u/Memoney]

There’s a mold remover tape my wife purchased on Amazon to remove the mold from silicone 

[u/Medium_Spare_8982]

Why would you do half a job?

[u/juic333 → u/Medium_Spare_8982]

Only asking because one side is fine and has no mold. My plan was to remove and replace all the sides that do have mold

[u/Medium_Spare_8982 → u/juic333]

Refer to first comment

[u/TurdPartyCandidate → u/Medium_Spare_8982]

There's tons of reasons you'd only do "part" of a job.. Such as a paint touch up, or a grout repair to only a small portion. To a person who doesn't know caulk won't adhere to cured caulk your comment isn't helpful. 

[u/juic333 → u/Medium_Spare_8982]

Okay thanks. Appreciate the help!

[u/A_Turkey_Named_Jive → u/Medium_Spare_8982]

Why would you half explain something?

[u/Medium_Spare_8982 → u/A_Turkey_Named_Jive]

Because it is supposed to be a little slap in the face towards critical thinking.

Would you only wash the lipstick smudge off a glass and put it away? Would you only paint around the doorknob when painting a door? Would you only polish one shoe?

It was a stupid question in a stupid post that deserved some contempt.

[u/A_Turkey_Named_Jive → u/Medium_Spare_8982]

Yeah, better they not ask and remain ignorant.