Silicone Caulk: How to Caulk a Shower or Bathtub
The problem: ‘Caulking’ with 100% silicone sealant can be quite frustrating.
First of all, it can create a huge mess, be almost impossible to clean up, and make your shower look uglier than before you started.
Latex, acrylic, and siliconized caulks aren’t the answer either as they are ineffective, don’t last, and can turn into mold. Read more about caulk vs silicone.
Finally, relief is here! This post will share a simple technique to get good-looking and clean caulk joints that you would swear were done by a professional. Except that professional is you!
This post contains affiliate links. The site owner may earn a commission should you click on an affiliate link and make a purchase. Read more
Caulking Tools Needed:
- caulk gun
- paper towels
- clean rag
- denatured alcohol
- empty spray bottle
- 1/4 inch foam backer rod
- Caulking tool (optional- can be your fingers)
Fill the spray bottle with denatured alcohol and proceed to the first step
How to caulk a bathtub or shower
Clean area that will be caulked
Spray some alcohol on a rag and wipe the area down that will receive the caulk.
You want to make sure that there’s a clean and dry surface for the silicone to adhere to. Because the alcohol evaporates quickly you shouldn’t have to wait long.
Backer rod:
Insert the backer rod into the gap.
The backer rod helps the performance of the caulk joint. Firstly, if you can get the backer rod in the gap then that indicates the joint is cleaned out which is a good thing.
Also, it keeps the silicone from being too deep and adhering to the back of the joint which is another plus.
The One Thing Every Tile Installation Needs: Movement Joints
I usually use a putty knife to stuff the foam backer rod in the joint but other tools will work as well. Mainly what you want to accomplish is to get the foam in the joint and not have it stick out.
Apply the silicone:
Using the caulk gun put a bead of silicone in the joint. Because you’ll be spraying the alcohol you want to make sure that the joint is well filled with no gaps.
Spray alcohol over the silicone sealant:
With your spray bottle spray denatured alcohol right over the caulk joint.
Tool the joint
The concept is that silicone won’t adhere to wherever the spray is. Consequently, when you tool the joint the silicone caulk shouldn’t make a big mess.
For tooling, I usually just use my fingers but they do make specific tools for just for this task.
However, you could use your own DIY tools as well. For instance, I’ve used popsicle sticks before with good success.
Wipe with a rag and alcohol
Spray some of the denatured alcohol on a rag and detail the joint as needed.
Corners
When it comes to a 3-sided corner I will usually caulk all three joints at once. If you did just one joint you’ll get alcohol into the other two if you spray the corner.
So I usually just caulk a 6-inch, or so, bead out of all three joints and meet up with them later.
Other silicone caulk tips:
Start at the bottom
Because you are spraying the alcohol it’s going to want to run downward.
Consequently, this presents a problem if you haven’t already done the joints below because the alcohol will run into the open joint and keep the silicone from sticking.
As a result, you’ll want to start at the bottom and work your way up.
Except when caulking around bathtubs
If you plan on caulking vertical wall corners and the tub rim at the same time then I don’t recommend doing the tub rim first. The reason being is that the tub tends to move.
This matters because if you caulk the tub rim then climb into the tub to reach the wall corners you will be flexing the fresh silicone caulk around the rim. It’s the same thing with a fiberglass shower base.
Due to this I recommend caulking the vertical wall joints first and then caulk the tub rim when you finish. Possibly you’ll have to wait a bit for the tub rim to dry before caulking this area.
That’s the crash course. Hopefully, this will be enough to convince you to leave the latex and siliconized caulks behind and install 100% colored silicone around your tile.
I use silicone caulk exclusively now, and I am not handy. I actually use masking tape to line both sides of where I am going to caulk, lay the bead down, smooth with my fingers, remove the tape, and run over the line again with my finger. I leave quite a small gap between the tape lines, because when I smooth it after removing the tape, it spreads the line of caulk out slightly. It actually looks like a professional did it!
Thanks for the comment. Tapping is another way of doing it and that works well also. Sometimes you don’t want alcohol on the surface that you’re caulking so taping is a good alternative way to tackle that.
I’ve seen recommendations to leave a short break in the caulk toward the front of the tub to let water drain out and and avoid leaks over the front edge of the tub into the adjacent wall. Sounds like opinions are pretty divided and it’s almost a regional thing. Do you have any opinions on leaving these weep holes in the caulking around a tub?
Some tubs have weep holes designed into them and, if this is the case, you’ll want to leave those open.
If its your own tub then you can handle it however you want. As a professional, leaving a gap is a guaranteed call back.
Additionally, just because a gap is installed doesn’t mean that water will find its way out as it’s not designed to exit through the weep hole. Some may get out but it’s not like there’s a pitch to the exit location.
But it would allow air to get back there and it may help in evaporation. It also leaves an area for mildew to collect.
I am attempting to replace grout around the tub with silicone caulk. I can see why the contractors that remodeled the home we purchased used grout because the marble tiles are not perfectly even and filling with grout must be easier than filling the gap then caulking over top. In some areas the gap between the tile wall and the tub is maybe 1 mm and 1/8″ in others. Is this a matter of getting different diameters of backer rod, filling in the appropriate size gap, and then caulking over that?
Probably not. You can pull backer rod and thin it out so the 1/4 inch backer rod should fit into 1/8 inch gaps and a little bit smaller. If it’s really tight then you won’t be able to get it into there.
Typically, I fit the backer rod in where I can and if it’s too tight I don’t worry about it. I’m probably supposed to tell you that you are supposed to fill it with something but if it’s that tight the silicone usually won’t go too deep anyway.
Thanks so much for this information. Is it best to grout the tiles first then do the corners. Also I have two different grout colors, bone and bright white. The bone is on the shower floor and bright white on the white subway tiles. Which color would you use at the btm joint realizing that some may blead into the the other where joints intersect. The btm is a 2″ mosaic with 4X the joints so I am thinking bone. Thanks again since I know know I have done these joints wrong forever.
The right way to caulk the joint around the tub is to fill the tub with water, which will open the joint as much as it can be opened. Then caulk/tool/etc. Let it set overnight with the tub full. Then drain the tub, which will put your shiny new caulk joint in compression. Note that all silicone caulking is designed to “stick” to adjacent surfaces 180 degrees apart – the two edges of the joint you’re caulking. It will always fail prematurely if it’s adhered on three sides (those two edges and the back of the joint) because the third side “stuck” prevents the joint from expanding/contracting freely – that’s why you should use a backer rod or other ‘bond breaker’ behind the joint if it’s deeper than about 1/8″ – something nobody does – which is one reason why caulk fails prematurely. Other reasons include trying to caulk over anything but pristine-clean surfaces, not completely filling the joint not tooling it correctly, etc. etc. There’s more to it than just squirting caulk in the joint and then spritzing with alcohol.
The caulk around the bottom could go either way but I always prefer to match the shower pan color- so in your case, bone.
You will have to be careful about it bleeding into the white and may have to touch up after the fact.
Years ago, when everything was tight joints and nonsanded grout we use to silicone first- then grout. But these days it’s rare that I do that. Almost always I grout first and caulk second.
Thanks for your comments!
A wealth of information in that single comment. Thank you!
If sanded grout is used, is it necessary to caulk vertical wall corners and around the tub or is grout sufficient? Thanks, Mike
If sanded grout is used, is it necessary to caulk the vertical wall corners and around the tub?
Sanded grout shouldn’t be used in the corners not around the tub. It doesn’t flex and will just end up cracking and molding.
Silicone caulk is something that could last for years of it’s done right.
I won’t go into long details, but we’re just finishing up a DIY cursed bathroom remodel. I ended up with a 3/8″ caulk line around the front edge of my shower niche. I’m not sure how my plan went awry, but it did. I’ve used silicone caulk and I know the niche and walls are waterproof. I’m the only one who uses the shower, but I don’t like the appearance. I was thinking I could take some of the glass accent tiles, cut them down to 1″ width, and make a picture frame around the niche by affixing the tiles on top of the existing tiles/silicone caulk. A little different, but more aesthetic than the 3/8″ line of caulk. What can I use to attach glass tile on top of silicone caulk? Thin set? Gorilla Glue? More cursed silicone?
So I am reading this at 2 am as I am frantically trying to find a fix to the horrible silicone caulking job the tile guy did on my new shower. Don’t need to give you the whole story-suffice to say the guy didn’t know how to use silicone caulk and instead of stopping right away-he continued on. We got a lot of the extra off using soap and a cloth-in my terror, I forgot I’d read to use alcohol. My plan is to remove the silicone and start again-with somebody who is experienced with silicone! I need removal advice.
I plan to use a razor and cut out as much of the new silicone as I can. I will then wipe residue with denatured alcohol or mineral spirits (which do you prefer?). What if I can’t get all the silicone out between the tiles-will the new silcone still work?
Thanks so much for any and all advice-I’m off to take a Tums and try to keep from throwing up over this disaster. BTW the actual grout job looks ok-just the silicone is a mess.
To remove the silicone, I’ve used a razor knife to get the majority of it. Then some silicone caulk remover from a home improvement store and a small brush will get there rest of it.
Then dry it out and recaulk using alcohol to keep it clean. That should work ok.
You mention meeting up with a previously done bead later on when doing 3-way corners. How long can you wait before joining two beads so they blend together? Is it safe to wait for the alcohol to evaporate?
Nevermind, you already answer that specific question in the video. 15 minutes. Sorry, should have payed attention better.
I don’t have an exact time and it is one of those things learned through experience but hard to define.
The alcohol evaporates quickly and that’s one advantage of using denatured alcohol to spray the silicone vs something like soapy water or Windex, which both work for this also. So 15 minutes isn’t a hard and fast rule. Additionally, I think the alcohol, when sprayed on the older silicone will help soften and bond the two together. So, probably over 15 minutes is OK but the concept is to not let it sit too long.
Is there a good way to smooth out silicone caulk once it’s set up? I got overambitious and gunned too much at once. It started setting by the time I got to tooling and now I have some rough bumpy sections where it started to skin over.
I don’t think there’s any way to do it. You can cut it out and redo it of you like.
I’ve been able to spot repair silicone before. You might try it and see how well it bonds to the existing.
What is your recommendation in regards to the idea of “weep holes” when working with an approx 1/4″ gap between the bottom of the tile and flat horizontal section of the edge on a pre fab fiberglass/acrylic shower base pan?
It was set up with hardyboard, coated with Redgard water proofing, and the gap between the board and rim of the pan sealed with urethane.
I see some recommendations for leaving the gap below the tile open, and others say to seal it with a bead of silicone, and since it would seem either could work, though differently it is a difficult call to caulk or not so thanks in advance for your opinion.
The theory on this is that water will travel to the silicone and not have a way out. I believe the reality is that it’s a non issue. If the shower or tub has a weep system designed into it then those need to be kept clear. But otherwise, I seal everything up.
Appreciate your reply!
There were not any weep holes in the pan so ended up sealing the gap with the leftover grout color match silicone.
Also since there was a section of tile and part of the base beyond where the glass enclosure was to be mounted I decided to create one small sweep hole at each end that will double as a way to see physically that water is getting behind the tile and needs to be checked (should that ever happen in the future).
Thanks again for all your efforts here!
I’m glad it was helpful!
Thank you for sharing your video, great info! I was taught that the bottom of a shower stall should have a convexed shape to aid in water runoff. Based on your video am I to assume that what I was taught is wrong & this is not needed?
I see no downside to having a convex shape at the bottom of the shower
Hi Jim. Found your site while doing a bathroom tile project and it’s very useful. Thanks for taking the time to share all this info.
I’m having a little trouble finding a definitive answer about the edge where tile meets with the bathtub. Should there be a gap (1/8 to 3/16″ or so) with no grout that is sealed with 100% silicone? Or should grout be in the gap between the tile and tub surface (in my case an acrylic tub) and then that is in turn sealed with 100% silicone? I saw in one of your videos how you used a backer rod in the gap, so is it best to not grout the tile/tub joint but instead put a foam backer rod in there before sealing with silicone?
Thanks again for your help and insights.
nick in seattle
The proper way is to leave a 1/8 inch gap between tile & tub. Fill the joint with backer rod then caulk with 100% silicone. The silicone joint is supposed to be twice as wide as it is deep. That’s the by-the-book way of treating that joint.
Thank you for the info and fast reply!
One more question. In this particular situation the Hardie cement board stops just above the tub flange (approx a 1/8″ gap). The gap is sealed with Wedi joint sealant. The flange is approx 1″. When installing the tiles, is it okay to adhere tile to the tub flange with thinset?
As long as the tiles aren’t too small I don’t see an issue with it
Does alcohol kill spray bottles? Seems like if I leave alcohol in a spray bottle, they stop pumping after a few days. Lost 2 good ones already that way. Do you empty them out and rinse after you use them?
I have them wear out after a while but I’ve not found it to kill spray bottles. I’ve used the same bottle for some months now and it’s just an empty bottle that I bought at a home improvement box store. It could be the bottles that they sell are more industrial than others? I don’t know.
Ive got a tile shower in the master bath of my moms house that is showing signs of curb failure or lack of acceptable waterproofing. Ripping it out isn’t an option for several months so my thought is to try to stop the bleed until I can get in and see just how extensive the damage is. My question is: should there be grout and silicone where the walls meet the floor or just silicone? Currently there is grout and some sort of caulking that isn’t 100% silicone and was clearly laid in by someone who didn’t know what they were doing.
If you are trying to seal up that gap then you want 100% silicone in there. No grout. No acrylic or “siliconized”. Urethane is also fine. Even if the caulk job is ugly it might help keep some of the water out until you can get to it.
Hi, quick question I can’t seem to find any dentures alcohol local like you have pictured that says can be used for cleaning glass. I have found some that say on the can Clean burning Alcohol appliance and Marine fuel. Not sure if this can be used, its definitely denatured, But seems to be the wrong type. Must not be popular anymore since no one has it in store. Would you recommend I use glass cleaner instead, or is dish soap better, if I use one of these options, how long should I wait for it to dry, thanks for all your help
Denatured alcohol is all the same whether it says that it cleans glass or not. It’s a fuel for camp stoves also. If you can’t find it you can use glass cleaner or soapy water. All of those options work for silicone.
Hi Jim, thanks for this site! I’m about to tile around my bathroom sink. The existing wall is t & g pine. I’m putting in a tile backslash. My question is this: if I screw 1/4″ backer board into the pine and tile almost to the top, is there a square cap tile made to use on the edge to hide the backer board? My tile consultant says no, that I should tile all the way to the edge and I’ll need to use a quarter round wood frame or something like that to finish it. What do you think?
Mostly this depends on the tile and the design. If your tile comes with some sort of trim that would work for that then that would be an obvious solution. Or, you could cut trim tiles down to go around this. I wrote a post on alternative trim options here.
A final possibility is to use a metal tile trim (#3 in the linked post above). Normally, these are designed to fit underneath the tile but I suppose you could find one deep enough to fit behind the backer board and trim both the tile and backer board edges.
There’s also the wood edging possibility that you had mentioned above. That’s about all I can think of. Hopefully, that helps.
I used GoBoard as my substrate, and have a couple of extra Pro Sealant tubes laying around. Can I use this instead of the backer rod underneath the caulk?
I just started tiling over the weekend, and it was the first time I’ve done walls. It was messy and challenging, but the extensive prep work paid off. Here’s a Google Photos link of my progress: https://photos.app.goo.gl/Q83ckuv7UGQSozb86
btw, the comment section in the GoBoard page only shows 1 comment, and clicking on ‘older comments’ only refreshed the page.
Weird, I’ve been having issues posting to this site lately. Let see if this one goes through.
My wife and I started tiling over the weekend, and since I have a couple of extra tubes of the GoBoard Pro Sealant, I was wondering what your thoughts are on using this instead of the backer rod to fill the tile gaps. Thanks!
Also, here’s a picture of my progress. Since it’s my first time tiling a wall, it was messy and challenging, but the extensive prep work paid off. Having a laser level also helped!
https://photos.app.goo.gl/qFZMhoYJAZazKJmd6
The backer rod is designed to be used with sealant and you can’t use a sealant in place of it. The point of it is to keep the sealant from bonding to it on the underneath side.
The reason that your comments weren’t showing is because of the links in them. The site filtered them out for me to manually approve in case they were spam. Hopefully, you’ll be white-listed from now on but I’m not sure if it the system is that smart.
Thanks for bringing the comments issues to my attention. I’ve made some changes to the site to try to speed it up and I will look into what the issue is with that page.
It looks good and flat and I like how you designed the niche. Thanks for updating us on your progress!
I had a feeling that was the case, in case someone was posting an unsavory or malicious link. That said, apologies for the multiple redundant posts!
I have 2 extra tubes of the sealant, and trying to think of ways to productively use it up. What’s your thoughts on using it to seal up the perimeter where the GoBoard meets the ceiling and/or floor, just to fully seal up the bathroom?
And thanks for whitelisting my links. I’ll be continuing to post my progress as I go along.
Yes, either one of those places would be fine. You’ll want to make sure that you tape off the ceiling so it doesn’t make a mess where you’ll need to paint.
Thanks. This was MONTHS in the making. The careful planning was mostly out of fear and paranoia. Even before tearing down the drywall, I’ve watched your GoBoard install video like 20 times!
Also, I’m a designer in advertising, so using graphics programs, I planned out every stud, GoBoard cuts and tiles. I also incorporated tub, toilet, and fixture specifications into it.
I threw some of the layouts into the same link as above:
https://photos.app.goo.gl/qFZMhoYJAZazKJmd6
I wish I had the skills with those graphics programs. It would help show the customer what things will look like. Thanks for sharing!
Using those programs was invaluable. It made planning so much more manageable. I added a few more images to that link—one of them is a 3D render of what the bathroom would look like when it’s all done, and all the fixtures are in.
The other images however, was a grave mistake I made—I accidentally installed a tile with a sliver cut out to fit the corner wall, but somehow never noticed it until the next day. Fortunately, the thinset wasn’t fully cured yet so removing it was much easier than anticipated. One thing I noticed was that the thinset didn’t really adhere to the GoBoard Sealant or to the GoBoard Seam Tape. I’m hoping it’s because the thinset wasn’t cured yet.
I was also disappointed by the lack of coverage. I should’ve pushed the tile a bit harder onto the wall.
Two things to keep in mind is that the bond will become greater as time goes on. Also, the bond only needs to meet or exceed 50psi. according to industry standards. So the bond may not seem great but I bet it was just fine.
Thanks for that affirmation. Everything I’ve read about tiling in wet areas is that it requires 95% coverage, so seeing that made me paranoid.
That said, I just completed tiling the bathroom walls today. It was truly a love hate experience, but I’ve learned a ton.
I added a few more images to the Google Photos link
https://photos.app.goo.gl/qFZMhoYJAZazKJmd6
Looks great! And the walls look nice and flat. Nice job!
Thank you!
However, there were a lot of hiccups and flaws—the back wall wasn’t completely plumb, so it was about 1/4″ further back than the base of the tub, so it was a joy measuring and cutting tiles. Also, another mistake I made was a lot of stopping and starting, so lippage and mis-alignment was a problem throughout. If I were to do it again, I’d at least get the baseline row installed, and then a column in the center first.
For those DIYers looking to use black grout, there are a LOT of caveats to that. One, a dark grout over white tiles WILL accentuate every single flaw, matter how invisible to the eye it seemed, and no matter how well you sand down that cut edge. There were also a few super-tiny chips on some of the edges that I wasn’t even aware of until grouting.
There were plenty of occasions where I’ve had the tiles stacked, and if they shift around without protection, the movement caused enough abrasion where it wasn’t visible, but enough for the pigment to seep into.
Some of the wedges from the leveling clips created some abrasion as well. That probably would’ve happened even if I handled every tile carefully.
Another dumb mistake was cleaning out thinset from the grout lines using a rigid putty knife. It created imperfections along the tile edge where the black grout showed through. Fortunately, I switched over to using a disposable razor knife, was was far more effective, and far less destructive.
I added additional pictures to the same link: https://photos.app.goo.gl/qFZMhoYJAZazKJmd6
Fortunately, an acid washer removed about 90-95% of the stains, but it was a major pain in the butt to rub them off.
Do you think it was a poor quality tile? Or do all tiles cause these stain-prone micro-scratches when stacked? These were $2/sq-ft porcelain rectified tiles from Lowes, so I’m not sure if it’s a get-what-you-pay-for situation.
All in all, I’m actually pretty happy with the results. It’s one of those situations where no one would be able to point out the flaws, but I know where they all are, and I have to learn to live with it.
Black grout is definitely no fun to work with as it gets all over everything and is difficult to remove. Additionally, some of the imperfections and damage from movement can happen with any tile. But I do think you experienced some issues because the tile is from Lowes. It’s a nice tile but it’s going to be of lower grade than similar tiles carried at specialty tile stores.
The bathroom still looks great and I appreciate your sharing your experience for the benefit of others.
I think your right. $2 a square foot was too good to be true for rectified porcelain tile. Since I was saving thousands of dollars by doing this myself, it wouldn’t have killed my budget to have spent more for quality.
I just finished tiling the floors last night. One lesson learned from doing the walls is to avoid stopping and starting on different days to avoid lippage and unevenness.
I encountered a problem with a couple of tiles marked in red in the link https://photos.app.goo.gl/qFZMhoYJAZazKJmd6 where they’re butting up against the wall. Prior to this, I did a complete dry fit of all the tiles, with the 1/8″ leveling spacers in them, and it was perfect, with 1/8″ movement joints all around. Will these tiles be an issue with movement? Or should I take an angle grinder and shave off a bit of the edge? Thanks!
The link isn’t working for me but there should definitely be a gap where they butt into the wall. If the gap disappeared then I would cut a bit out to allow for movement.
Might be a typo. You can click the same link I posted earlier.
You’ll need a little space in there. Even if it’s not a full 1/8 inch. It’s difficult to get everything to go in the exact same as when it was dry laid so 2 small spots should be considered a win.
Yeah, it was a little infuriating at the time, because I’ve done my due diligence by measuring over and over before and after dry fitting every last piece, so each millimeter was accounted for. I underestimated how a sliver of drywall between spacers can quickly derail all that effort.
I’m finally getting to the point of grouting and sealing my tub enclosure. Couple of questions. I know you’re supposed to use silicon wherever there’s a plane change. This is obvious on the end & back walls, and along the tub itself. What about the outside (convex) corners of niches or, more specifically in my case, a windowsill which has bullnose on the sill meeting the subway tile on the wall? This is an outside (convex) corner. Should it be siliconed? Elsewhere, I have a 2″ jog in the wall which I used radius tiles to go around. Should I silicone the curved end of the radius tile, or is it OK to simply grout this joint?
Also I am inclined to do the sealing before the grouting. Otherwise it seems like it would be harder to keep grout out of the corners where I’m going to seal. I’m not in any hurry so I have plenty of time to let the alcohol dry. In another comment you said this used to be the standard technique, but you don’t exactly explain why it changed.
While there’s an argument to be made for putting the sealant in the outside corners it’s rarely done. I would recommend just grouting the outside corners unless you start seeing cracks. The silicone will stand out more on the outside edges rather than the inside corners.
I’m not sure that I’m visualizing your rounded inside corner correctly but I think you will want to silicone each side of this corner piece if this corner piece is on the inside corner. On an outside corner, you are probably good to use grout on it. Is this maybe a quarter round piece?
The reason many don’t silicone first any more is because tile styles have changed. Tight joint 4.25 and 6-inch ceramic tiles were common to silicone first. Once tile got bigger and the grout joints opened up then it stopped. It’s difficult to keep a consistent sealant line when the silicone falls into the grout joints. So, grouting first and cleaning out the corner later became the norm.
Good questions!
Thank you for the fast reply! I will grout those outside corners. The radius tile I was talking about is not an inside corner, it’s another outside corner that I did a different way, not using bullnose but using radius tiles instead. It’s not a quarter round; it’s an actual official radius tile, part of the very common Home Depot Restore subway tile line. On the box it’s labeled 2 x 6 radius bullnose, Home Depot Store SKU # 1002655464.
Anyway, for the question of silicone first or grout first, after doing more reading I think I’ll stuff some thick string (or maybe sacrificial backer rod, I have lots) in those inside corners on the tub enclosure, grout, then carefully pull out the string. This is supposed to keep the grout line clear for later backer rod+silicone.
I see the tile that you are talking about. It’s probably not a bad idea to silicone the short end of that piece. The longer side of the tile will be better adhered and could cause some flexing on the short side.