This shouldn't be filled. A gap at the bottom of the wall prevents water from climbing up behind the wall by capillary action.

As long as its waterproofed behind there this is correct. Makes it tougher to clean tho.

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Maybe put some weather strip in first then caulk over? I'd probably look into plumbers putty as another option that can take caulk over it.

You can use a thing called backer rod make just for prefilling large gaps prior to caulking they come in different thicknesses and are shoved into gap prior to caulking, gives caulking something to hold onto and if this is a wet area 100% silicone needs to be used. When applying silicone put blue painters tape at the edges of where you want silicone to stop,install silicone then Cann lick finger and wipe one side to other to make sure it's in good. Let set an hour and peel blue tape off should be nice neat line of caulk.Wait at least 12 hours then use shower without fear of water damage.

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It also allows your shower to leak water into the wall

lol

A gap at the bottom won't stop water from working its way up since capillary action will "pull" the water up. And the gaps will get super gross unless it's constantly cleaned.

Not if your wall is properly waterproofed. Red guard on the wall with a seal to the floor membrane, then tile or surround with a gap at the bottom. Standard stuff.

I would argue that old, nasty caulk under there is more difficult to clean. And mold behind the surround or water damaged drywall is much more difficult to deal with.

That's not true. The gap allows a pressure break so the water can just spill right back into the pan.

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Wow, big gap, I wonder why it was done like that. I suggest the backer rod then fill the shower full of water with the drain covered to weigh it down. Then use 100% neutral curing silicone. If it's just white GE makes one that is guaranteed to not mold. I have used it and it's very good. I believe it's call Supreme. Just make sure you us a Neutral curing silicone. You can get it color matched through Mapei, Laticrete etc.

Most big box stores will carry it. Do not use caulk or Siliconized caulk. On all change of planes you must use 100% silicone. Caulk is just gonna crack. Use a smoothing tool to put the silicone in and a spray bottle with water and a couple of drops of Dawn. It will give you professional results. Once put on give it a long time to cure as that is one huge gap. Then drain the water and you should be good to go.

Are you sure the tray hasn't dropped? Looks to me like there was sealer there but it's degraded and split as the tray dropped.

You can clean it out and fill it flush with sanded grout.

After the grout is dry go over it with clear silicone.

Chose a grout that is much lighter than the rest of the grout as the silicone will darken the grout you applied in the crack.

It’s not a perfect solution but it does work.

I had a similar issue - I used pvc 1/2" round and then caulked it with marine grade caulk (more like epoxy iirc). It's been good for over 10 years now & still looks good to boot.

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As others have said:

1.) Remove old caulking. razor blade and peel should do the trick.

2.) Clean the area with a blue non scratch scotch bright pad and some shower cleaner to remove any remaining caulk. (Soap and water is probably best careful of cleaner with alcohol as it will get trapped and reduce the bond of the caulk. Be sure to let the area dry before caulking no matter what you use.)

3.) Apply backer rod; also called rope caulk, or filler rope, in gap, be sure to use appropriate size backer rod for wet areas, typically silicon. Snug but not packed in. You want it to be receded a consistent distance. (For deep areas you can stuff a smaller piece of rod farther back then stick the main single piece in front of that.)

4.) Apply painters tape above and below the gap ~1/4" from area you'll be caulking. I'd suggest using 1" tape because you'll likely be using quite a bit of caulking, especially if this is the first time for you, to cover that area and when you smooth it out you wanna be sure the tape is wide enough to catch excess.

5.) Apply silicone bathroom caulking, I like 'Alex Flex" but if it's cold where you are be sure to verify the caulk will set within the temperature, especially If there is cold outside are coming out via the crack. They make more expensive caulk for colder settings.

6.) smooth out with silicone caulk applicator. You can use your finger but with large gaps you'll have better luck with an applicator.

7.) Remove painter's tape prior to drying. sometimes you can run over the caulk again with the applicator to smooth out the transition from where tape was removed.

8.) Let dry for 24 hours prior to use, lightly touch to make sure the caulk is firm and you're good to go. (12 hours maybe enough dry time but with such a large gap and winter upon us, more time is recommended.)

Hope that helps, good luck.

Silicone is pretty strong and a larger gap actually allows it to absord more movement. With the backer rod it will sit just nicely.

Grout is water permeable and will actually allow water to leak behind causing damage.

Silicone all the way.

Backer rod is the answer.

Like anything is going to be properly done and still contain a gap like this.

You're probably right, lol

So:

Scrape/clean out all the old silicone / mold

Clear area with 90% isopropyl to kill mold/moisture. Let that dry/breath for 24h

As other have said, buy some bathroom/tile backing rod and jam it in there this will give an anchor point for the next step, the gap here looks about the widest end of a tile spacer so someone likely put a bunch at the bottom for some reason, and leveled the tiles from there, maybe an uneven tub or floor idk.

Once dry, fill your bathtub with water to weigh it down

Fill the remaining _\ gap with Microban Silicone. Microban or similar generic bathroom specific silicone not regular silicone.

This will prevent mold buildup, regular silicone will be black within 3y

Let silicone dry 72H yes it is a pain in the ass to not use the shower for 72 Hours. You can get away with 48 but if possible give it a full 3 days to cure. Plastic line your shower and run a fan if you must.

Buy more silicone than you think, it won't go very far and depending on how well you do it you might need to do a little touch up.

For a nice seam there is a tool to round it or a bit of canola oil on the finger and smooth the silicone out manually leaving a good amount as it will shrink and pull inwards

Good luck.

Plumbers putty will dry up and crack away of used to fill that gap, won't provide a water tight surface, and would take a lot to fill that. Backer rod would be the appropriate backing for silicone, not caulk

I've done this before. The grout will crack because it's brittle and the shower pan and walls expand and contract at different rates depending on temp and humidity. You need something stretchy like silicone for any transition in surface, even inside corners of the same kind of surface.

Absolutely should NOT be grouted. Never grout a change of plane like this.

This person calks

One small note, sealant needs an hourglass sort of shape to expand and contract at the thinner middle part, with the wider top/bottom having more contact with the surfaces. So even using a backer rod when it’s not really “needed” for shallower joints between parallel surfaces can still help, if there’s room.

Do backer rods work for baseboard gaps? Was planning on shoe molding throughout the house but between cutting and painting it would become quite a project.

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You’re better off with quarter round. Caulking that much linear footage sucks compared to chopping shoe molding with a miter saw

You'll get better adhesion to the shower floor and tile if, instead of using a finger, you use a profiling tool (ideally an angled one, not a concave curve that you'd get with the finger).

Concave silicone in areas that get a lot of water (like showers) mean the part that is doing most of the 'work' to keep water in the shower (where the top and bottom edges of the silicone meet their respective surfaces) is often very thin. A suitable straight angle avoids this issue.

One other good thing to do is wipe the area thoroughly with isopropyl alcohol before applying the silicone (giving enough time for it to effervesce evaporate away). Silicone hates soap residues, grit, and especially grease (another reason not to use a finger!), and alcohol is great at getting rid of all three.

Don’t use the polyseamseal! It gets very hard and brittle. Silicone is the best bet.

> I wonder why it was done like that.

To me it looks like the pan has settled.

Huge caulk

Shoe always looks better than quarter round imo.

Quarter round also takes up an annoying amount of space when you want to sit furniture flush against a wall.

Fill the tub with water before you caulk as well. The weight of the water can cause the tub to slightly lower.

I should think you could get a butyl (gasket material) seal that will fill the void and then use silicone to lock that in place and seal it all up

>effervesce

I think you mean evaporate. Isopropyl alcohol doesn't have bubbles. Yes, nitpicky grammar nazi-ish I know. That's how I roll.

Edit: I should have added that this sounds like a sound approach to resolving the problem but I'm not a professional.

Exactly.

Scrape out the caulking and use grout , seal the grout.

Nice Caulk

Black caulk fills the biggest gaps. (That’s what I have been told.) I have only ever seen white caulk.

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This guys caulks

Isn’t that a bad idea? The grout can crack from tub movement

I’ve always heard to never caulk the baseboard (or shoe molding) to the floor. Something about too much movement between these surfaces causing caulking to crack/separate). (Except, I think, in bathrooms, for purposes of keeping water on the floor from getting underneath). The alternative to shoe molding would be to pull the baseboards and scribe them to the floor (basically trace the contour of the floor and shave off the bottom edge so it sits tight against the floor). Also agree shoe molding looks much better than quarter round.

Bathroom grade white silicone will be absolutely good you just need to apply it properly.

Gloves. Wet your GLOVED finger. It’s hard to really get off skin.

This is a great post, but Alex Flex is not the right stuff for this application. Alex Flex is a siliconized acrylic latex meant for painting projects. It’s not supposed to be in wet areas. The only thing I’m aware of that should be used here is 100% silicone.

Thanks! I'm doing this now

Thanks for the detailed advice!

Thanks! I think the gap is there because the installer wanted to make the shower floor sloped for drainage. The existing caulk is my first attempt at sealing it.

Thanks! I appreciate the drying time tip especially. I'm sure i didn't wait long enough last time.

No problem 👍☺️

Thanks!

Thanks for your experience!

You will have to do it in stages. I have a corner shower that I redid. On the big gaps, put a base bead in, then leave it alone to dry. That’s how I did mine. Obviously take that old caulking out, clean it, then start over.

Some Siliconized acrylic latex is rated for wet areas. Any tub and shower caulk that’s not 100% silicone will probably be siliconized acrylic latex.

That’s true, and they’re definitely easier to work with, but Alex Flex is definitely not the right thing to use here. If not pure silicone, should definitely be using something that states for use in tubs and showers for this application.

Why not grout it ?

That's not how capillary action works. There is no "pressure" with capillary action.

And for the love of god if this this is a tub and not just a shower pan, FILL THE TUB WITH WATER before you caulk. You need to weight the tub down before the caulk is applied so it’s applied when the tub is maximally displaced.

Made me smile

I thought that was only for floating floors that aren't attached to the subfloor.

Yes, and in addition to creating a joint that is attached on only 2 sides and can flex properly, it will also solve OP's problem of too much sealant oozing out while drying.

By using less sealant, properly adhered with a backer rod, all of it will perform better.

Yes that's true. Technically it's surface tension. I figured it would just be simpler for others to understand if I said pressure break. And it doesn't change the point of having a gap.

I noticed our friend here said to wait an hour before pulling your tape. Not to nitpick but I was taught to pull your tape immediately after your final swipe. But what do I know, I don’t even tape when I do these types of caulk jobs.

Yeah, backer rod is what I was thinking. It's basically the same thing as the weather strip tubes, different sections of the store for sure.

I guess I grew up using caulk as a general term for anything that covered a joint, be it silicon or traditional stuff. OP should choose their goop for their situation.

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Happy to help.

As one of the replies to my post said Alex Flex may not be the "best" option compared to a 100% silicon caulking alternative. That said Alex Flex is marketed as 100% water proof, so long as it is not submerged. In my experience it would work fine in this application since it's above the tubs water line but 100% silicone is better.

Edit: I'd probably go with something like GE's "supreme silicone kitchen and bath" for a 100% silicone option. It's readily available.

Fair point. The 100% silicone is the best option. Honestly never paid attention to the fact it was a mix. Alex Flex is commonly available, "100% waterproof" (when not submerged), and often cheaper though.

Since the area in question is above the tubs water line it would do the job fine but you are right, 100% silicone is better so long as you don't want/need to paint the area.

This is good, but to dress it up better use denatured alcohol and a tool to smooth it out.

https://youtu.be/ExlfAGdssR8

Thanks, grammar angel on my shoulder! You are correct, though effervesce is a much more fun word to say.

Yeah whoever flipped my house just grout in places like this. It all cracked within the first year. Pretty annoying I must say

Quarter round

I've used silicone meant for pools and the back of a spoon to smooth the seam. This has held for several years.

Silicone will start drying before you finish applying, tape will pull it off more the longer you wait. I don’t use tape My choice 1 -That needs to be cleared out first. 2-You can use a silicone grout that matches the existing grout or Try Amp caulking very little sag. Just a simple reminder there’s a 1/4-1/2 “ lip extending upward on that tub you can’t see. Curious if that sub floor is sagging

This makes sense. I hadn't thought of this.

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I’m really NOT liking what I’m seeing here. I have extreme doubts that the water has not penetrated the surface and is now behind the wall. Eventually an entire wall of tile is going to end up coming loose. I would put the likelihood of this at 90%. It won’t happen tomorrow or the next day but eventually it will.

If this is your home I would get it taken care when funds allow. I would recommend not showering in there for a few days and even put a small box tan or whatever pointing at that joint just to get some airflow going to make sure it’s to reduce any moisture that has penetrated the surface. If it’s a rental, I’d recommend using the backer rod and a silicone caulk. It’s not ideal but at least it should stop it from getting exponentially worse.

I really hate saying this because I’m not bragging but just to give a background. I’ve owned a flooring company for 34 years specializing in all sorts of tile, remodels, etc. We have done everything from residential homes, schools, hospitals, to military bases, etc.