Caulk Caulking over Grout may be OK okay good bad shower tub


Old 12-30-16, 05:52 PM
Thread Starter
Join Date: Jul 2014
Location: usa
Posts: 218
Caulk Caulking over Grout may be OK okay good bad shower tub

I had a situation where I pretty much just had to caulk over grout in a shower. I read much info saying it shouldn't be done. I know that all the inside corners of a shower/tub should be caulked when first built to allow expansion when the tub is filled and from winter/summer frame expansion/contraction. A lot of the times, the installers take the easy way out and just grout those joints while they grout between the tiles.

Best practive of couse would be to remove the grout and then caulk it. They have electric grout removal tools probably around $50 that you may only ever need once but should be well worth the price vs a $5 manual caulk scraper. A filed down flat scrwedriver and a utility knife might also help. It takes forever manually and it like digging out of a jail cell but you'll get it eventually.

Here's what I think it boils down to: If you caulk over black moldy grout, the mold can bleed through and turn the caulk moldy. I don't thikn anyone's mentioned that in debates online about caulk over grout. Any moldy grout should be removed first, and then use bleach and/or a grout mold killer and scrub it really well and then I clean it out with mineral spirits and then do a few rounds of washing out the joints with just water and then allow it to fully dry before caulking. To dry it faster instead of not using the shower for at least a full day, you can use a heat gun on low setting or a hair dryer.

Another reason not to leave the grout there is that if you just caulk over the grout, the caulk will be very thin and not perform well for expansion/contraction and may end up splitting thus lettiing moisture in behind the caulk and won't breathe out easily through such a small rip in the caulk and thus ends up more moldy and probably have to definitly remove all the grout at that point which is harder than just removing grout because the rubbery caulk will interfeir with the gritty blade of a caulk removing tool. Caulk removers don't work very well either on silicone or 'bathroom tub caulk'. You have to let them sit for some time and do many rounds until the caulk comes off. It's a double edge sword. It's like paint remover. When you're installing the paint or caulk, you of course want the strongest bond you can get but when it comes times to strip caulk or paint, it's not as easy as you would like.

Another reason not to caulk over grout is you have to make the caulk slightly wider than the grout to hide it and may end up with a really wide caulk joint, which is fine but some people might really not want that.

The situation I was dealing with was a tiled shower ceiling with molded grout lines. I was told it needed to be recaulked but they mistook the grout for caulk. Most people don't open the shower door/curtain and the window and/or use the exhaust fan after a shower, which greatly reduces bathroom mold/moisture issues such as moldy grout or black mold dots on the celing. The black mold dots on ceilings can usually be eliminated by spraying bleach and wiping with a rag and may not even need painting. Bleach kills mold and doesn't just clean it. If you have a heat vent in the bathroom, even if it's closed, I can understand not opening the window in winter, but in other seasons, it's much better for the drywall etc to open the window and shower door/curtain for maybe 15 mins after a shower.

Anyway, I started scraping this grout out but then realized there's probably a product at hardware stores that will clean mold from grout. I went and bought that (zap brand which got great reviews) but I did like 5 rounds with it and it didn't really help. The grout in the inside corner joints is just too thick for the product to penetrate. However, the thinner grout lines between each tile came out okay from using the grout mold cleaner product and a stiff grout cleaning brush.

The thing about this shower was that the grout lines on the ceiling had rippled tiles as borders and thus the grout lines were all wavy. It could have taken days to scrape out manually and can't use an Oscillating type electric grout removal tool for that, but should be able to use the type like the HYDE Regrout Tool that is basically like a mini chipping hammer/jack hammer for comparison. A spinning dremel removal tool might have worked also but these tools you need most likely need to be ordered online in advance. Be careful not to crack any tiles with the chipping type tool because most older showers, you'll never find the exact match tiles to replace it. Side note, if you have really tight grout lines in between tiles (shoudln't really find joints so tight on inside corners), if you have the really close tiles, the only way to remove the grout may be a razor blade or a sharpened flat head screwdriver.

So anyway, what I meant to say is I ended up caulking over the wavy grout lines. Again, if you do this, I would at least scrub them with bleach and/or a grout mold killer product and then rinse with mineral sprits and then rinse may times with water and allow to fully dry so that the mold in the grout is less likely to bleed through the new caulk. You want the mineral spirits to lift out any greasy residue from grout cleaner/caulk remover and then wash that out with water a few times and get the grout really dry so the caulk adheres well.

Which leads me to caulk. I see a lot of people in 'caulk over grout?' threads suggesting to use %100 silicone. I would highly suggest to use a caulk specifically made for tub and bathroom/sink instead of just pure silicone. These tub/sink caulks are specially made in a lab for this purpose, and may also adhere to tiles better. Spend the extra ~$3 per tube and get the ones that say they have a 7-10 year guarantee against mold (which some other %100 silicone don't say). It is true that these mold-free tub caulks sometimes also say that they are %100 silicone, but other %100 silicone caulks don't say this and don't say that they are meant for showers/sinks etc so don't get them confused. I also found one that says lifetime guarantee against mold and I use that, but remember, if you caulked over moldy grout, then it still may bleed through.

Tub and sink bathroom caulk is very slippery and greasy and can be difficult to correct errors when making the final swiping of it if it gets on the tiles. If you have contrasting tile and grout colors (white caulk and dark tiles) I would highly suggest to tape the caulk lines first. Check youtube for tape grout perfect grout etc and you'll see how to do that. It's pretty easy and should be actually faster than having to very carefully smooth the caulk line with your finger and avoid making a mess on the tiles. Make the tape edge about 1/8" past the existing grout line to hide it.

Another thing about using the tape is you can make a slightly thicker caulk joint. Remember, the grout is right behind it, so just smearing caulk over it with your finger will leave only a very thin layer of caulk that can crack during expansion and lead to having to remove everything. With the tape method, you can put the caulk on pretty thick and then barely swipe it smooth with yoru finger so you don't press it down a lot, and then you immediately remove the tape for a clean line, don't let it dry at all. After removing the tape, you may end up with a sort of ledge/lip at the edge of the caulk because it was put on thick, but this lip is ok in most places especially vertical lines but I would try to avoid it at the top edge of the caulk on a horizontal caulk line where the tub or shower floor meets that wall because water can collect on top of that lip and lead to mold. in other words, you can still make that caulk joint thick but when you smear it smooth, put a bit more emphasis on the top edge so it doesn't create as much of a lip, but still keeping it a thick caulk joint.

The actual perfect way to install caulk is to have it only adhere on two of its 4 'sides'. Which basically means one side is behind it, another side is the front face you see, and then there's the right and left sides. When only 2 sides are adhered to a surface, it allows the caulk to expand and contract better. This is why caulk backer rod is preffered for many situations. There is also a minimam thickness and width that caulk manufacturers specify on the label or on websites because too little caulk won't stretch well. If you do a google image search for caulk backer rod, you will see what the 2 sides thing means. You wouldn't put backer rod in a shower even if it was newly built because backer rod is usually too thick for that joint and also there's a bit of dead space behind the caulk in the inside corners anyway, so you sill get only 2 connection points. But when you caulk over grout (or over anything for that matter where there's no dead space behind it, you end up with the caulk adhering on 3 of the 4 sides instead of just 2. And this can lead to it cracking during expansion/contraction. But again, it is what it is if you feel you must caulk over grout or caulk over something outside that is already a tight joint and ends up with the backside of the caulk adhering to a surface along with two 'sides' of the caulk.

Another thing I've seen mentioned is if caulking a cracked tile is ok, which because of the 3 side connection thing isn't the best thing to do, but if you can't find a matching replacement tile or just don't want to remove the tile, then using tub caulk over the crack line should be fine. Just keep and eye on it. But if you have a decent amount of grout lines that flaked out and you want to simply caulk them instead of grout, I would recommend grout if it's a decent amound. Grout can be sort of a process, and some require two parts from seperate products and end up costing maybe $30 of materials for the smallest amount you can buy vs just a $7 thing of caulk that can be done quickly. Try and find a small container of grout that doesn't need another part/product to it, and possibly get an additive. I'm not going to list all the info about sanded vs non sanded grout and additives, but it depends on wall/floor and the size of the joints. Also sealers, even when sealed, the grout is still meant to breathe, which is why I would suggest to use grout if there's a decent amount of lines between the tiles that have flaked out and need repair. Because you don't want to seal the moisture in with caulk and possibly cause mold or water damage to the wall or possibly an electrical outlet on the other side of the wall etc. However, maybe the sanded caulks they sell near the grouts are meant to also breathe and you can use that instead. Yes when the shower inside corners are caulked and no groute is used (which is the correct way), you seal those areas but it's not enough to cause damage, but caulking a decent potion of a wall instead of regrouting could lead to a problem.
Sponsored Links
Old 12-30-16, 08:15 PM
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 18,709
I'm sorry, but do you seriously expect someone to read such a long post?
Old 12-31-16, 03:48 PM
Thread Starter
Join Date: Jul 2014
Location: usa
Posts: 218
lol right. But I copy pasted it and will greatly consolidate it for my own notes. I figured there were a lot of threads and reddits etc when I googled about this and I felt the need to add my experience, it just sort of ended up a huge article.
Old 12-31-16, 04:41 PM
czizzi's Avatar
Forum Topic Moderator
Join Date: Jul 2007
Location: USA
Posts: 7,203
As a contractor who does tile, I want to say that this is terrible advice on many levels. I have done repairs to showers that were over caulked instead of re-grouted and the results were as expected. Constant mold issues everywhere and as caulk tends to fail over time caused water to seep behind the caulk and infiltrate the wallboard behind the tile. This happened to be an older home that used drywall behind the tile. The result was a failed wall structure and a fairly expensive tear out and replace. So, where ever you copy and pasted your notes from, it was not from a reputable professional site. Experience and first hand knowledge say that you don;t know what you are talking about.

Yes, re-grouting is a pain, yes we would love to find easier ways, but I will not advocate to any of the members or guest reading this a method that is a short term fix and something that will fail in the long run. Invest the time and sweat equity and do it right the first time. There are many ways to fail and only a few ways to succeed.

For the record, I DID read your whole post.
Old 01-02-17, 07:46 PM
Thread Starter
Join Date: Jul 2014
Location: usa
Posts: 218
well, I'm not trying to persuade anyone to caulk over grout. I made it clear at the start that caulking over grout is a no no.

I have done repairs to showers that were over caulked instead of re-grouted and the results were as expected

You aint supposed to grout inside corners. I think you know but just saying. Maybe there's flexible enough grout for inside corners but I would caulk. On a wall/floor, yea it should be grouted (or possibly the grout caulk tube sold near grouts is breathable and acceptable). I addressed this:

...Another thing I've seen mentioned is if caulking a cracked tile is ok, which because of the 3 side connection thing isn't the best thing to do, but if you can't find a matching replacement tile or just don't want to remove the tile, then using tub caulk over the crack line should be fine. Just keep an eye on it. But if you have a decent amount of grout lines that flaked out and you want to simply caulk them instead of grout, I would recommend grout

Bottom line is people grout over caulk all the time regardless if they might already read it was wrong.
Even this contractor suggests you can caulk over with sanded or unsanded caulk, but he does also say the better way is to remove grout first *****

I gave options if someone simply refuses to remove all the grout or watched that video etc. In short: scrub with grout cleaner/bleach first, rinse, dry, use the right caulk and put a thick bead so it doesn't tare as easily when expanding.

The whole post stemmed from dealing with a wavy grout line that would need specialty tools ordered to remove. Deadline was just a couple days away and the shower owner was informed that caulking over grout wasn't the best option but it was ok'd. I was told it needed to be 'recaulked'.
The ceiling was tiled and inside ceiling corners had these wavy grout lines. The rest were straight grout lines I removed.
I ordering a tool so 1/16" that lines my oscillating tool is too big for, and the rare wavy grout aren't an issue.

Last edited by Shadeladie; 01-03-17 at 05:41 AM. Reason: Link removed

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes