That pesky tub flange. You have the tile backer board installed and everything is waterproofed.
Everything except that gap between the backer board and the tub flange. How do you waterproof that?
Estimated reading time: 4 minutes
How to waterproof the tub flange?
To begin with, you can try reading the instructions for the backer board… which then will reveal… nothing.
What about the waterproofing instructions? More nothing. While the tubs themselves usually have some information they differ from brand to brand.
So what do you do?
Well, I’m going to give you three different ways to seal the backer board at the tub flange.
1. Caulk the gap
Probably the simplest way is to caulk the gap with 100% silicone or a urethane sealant.
First, you would waterproof with your favorite liquid waterproofing membrane of choice. In these photos, I used Hydroban liquid waterproofing by Laticrete.
Ideally, you would leave a 1/8 inch gap which would then have the sealant applied to it.
Either stopping the cement board above the tub flange or alternately shimming it out and dropping it down near the tub would both be good options.
Shimming it out is probably only feasible if the tub has a really skinny flange like a lot of the steel tubs do.
2. Band the flange
Another option is to use some of the waterproof banding material that’s available with some of the sheet membrane systems.
Something like Kerdi-Band or another version. Schluter has some good information about this procedure on their website and in this video:
They show using Kerdi-fix, on the tub flange and thinset mortar on the backer board. Then embed Kerdi-band into those adhesives.
3. Seal and (mesh) tape the seam
This is what I’ve been doing lately. I usually have some Wedi sealant in my van and have been placing 2-inch alkaline-resistant mesh tape over the seam and gluing it with Wedi glue.
Utilize whatever you have- Wedi glue, Kerdi fix, or a waterproof polyurethane sealant from a hardware store.
Using a small putty knife spread the sealant smooth across the mesh tape. The mesh tape makes me feel a little better about bridging that seam.
The reason that I don’t recommend the mesh tape with step one (silicone) is that the silicone will act as a bond breaker to thinset if it’s smeared over the surface.
With Wedi sealant (or something similar), you can adhere tile to the surface of it. So with method #1, you want to keep the sealant as clean as possible and in the gap only- not on the surface.
For additional information on mesh tape and backer board please refer to this post.
There you have it. Three different ways to treat the tub seam. None according to instructions. All preferable to doing nothing.
Jason Jay says
I sent you an email and then saw the note that we should leave a message in the comment section.
The short story, (long in email). According to my plumber, I have flex in my shower floor. I’m using a Durock shower kit. Followed instructions, but plumber thinks the thinset was too thin and is crumbling. Called his tile guy and they suggested the following: buy can foam, drill down to thinset, inject foam, and hope it works. My concern, since all there is a styrofoam fleece and waterproof membrane over the thinset, won’t this balloon the floor? Should I put down some weight on the floor? Before or right after the foam? This is a last ditch before ripping the floor out and starting over. And if that happens, we’ve already tiled the walls, so is there anything I can do to save the wall tiles?
It’s hard to know if the foam will solve the problem, or not. You could try it and see if it takes the flexing out. I think weighting the pan immediately after injecting the foam would be a good idea. Also, you’ll want to make sure that you patch any holes that you put through the waterproofing which is the shower pan.
If you need to replace the pan you will need access to the joint around the perimeter where the wallboard meets the shower pan. If this is already tiled then this row of tile will need to be removed.
Hello, great blog. Thank you for putting all this together.
If you caulk the gap then does the waterproofing membrane interfere with silicon adhering and do you have to get the membrane into the gap to cover the edge of the board so you don’t end up with a bare seem between the membrane and silicone?
Would the liquid membrane adhere to the tub flange? Can you cover the tub-to-backer gap with fabric strip and liquid membrane?
I find that it works best to apply the liquid waterproofing membrane first, let it dry, and then use the urethane across the gap. The urethane will stick to the waterproofing but the waterproofing won’t stick as well to the urethane.
You could just waterproof all the way down and use fabric like you mentioned. But I think it’s advisable to scratch the tub flange up with sandpaper, or something, to help adhesion. Also, the gap between the tub should be filled with something. Preferably something flexible which is why I like urethane and tape for this.
Ok, got it. Is the tape there for thinset to grab on to? When you put tiles over the flange, do you cover the seam and flange with thinset and adhere the tile onto it or do you just let the tiles hang over the flange leaving a void behind it? Would water get in there and sit on top of the silicone seal at the bottom?
What do you do where the backer joins the tub at the very edge of the flange and on the side? More caulking? I’m hung up on the edge cases, as you might see from my posts. Backer-to-backer and backer-to-drywall seams and corners are relatively straight forward and at least well covered but I don’t often see what to do where the surface meets plastic or enamel (i.e. window or tub). It would be awesome if you could do a blog post on this.
Thank you for your answers, both here and to my other posts.
If the flange is flush with the drywall then I thinset the whole space. If it’s set back in then it depends but usually I’ll keep that gap clean. It is theoretically possible for water to collect there behind the silicone gap. It’s nice if you have a tub with weep holes but not all tubs have them. Weep holes are indentations near the front of the tub designed to let water out before going over the edge. If your tub has them- don’t grout them in.
For the sides of the tub I caulk to the backer board. Here I will tape it off so it doesn’t make a big mess. You do have to be a little more neat and clean in this space as the tile won’t cover as much of the seam as it does at the flange.
I’ll look and see if I have a photo of caulking to a window or tub. If I do I’ll post it on my Twitter account (@Diytileguy).
If the tiles are hanging over a gap, will there be a problem applying the grout because there’s not a gap with a bottom to pack it into? Will it all just play-doh factory into the void behind the tiles? Can you place backer rod in front of the flange and thinset the tiles over it just so there’s a backing?
Yes. That would be an option.
One more question: Do you do anything to waterproof the screws holding the flange to the studs?
Thank you for your answers.
The technique above will put waterproofing over the screws. I don’t do anything besides that.
This is so helpful. Thank you for all you do. Forums are a mess and this is a nice refreshing place to get info.
I did a version of your first suggestion and caulked the gap between the backerboard (Hardie) and the flange. Some of the caulk smeared between 1/2 inch 1 inch onto the bottom of the backer board. I tried to scrape most of it off but it soaked into the board pretty good. Then I applied RedGard down to the caulk line. Then I went over with silicone again on some of the places where the RedGard was peeling off the caulk. It is sealed and holding fine now. Is it reasonable to expect it will continue to do so or did I do something wrong? One end of the tub is already covered in tile, so I could rip it out and redo it if necessary, but I’m not excited about that.
It sounds to me like you’re probably ok and that you have the entire board covered. Thanks for the comments!
scott hamilton says
My customer has one of those big vinyl rimless (flangless) tubs. This means that when they fill the tub it will probably flex down. I will be using Kerdi on the walls. What is the best method of water proofing the gap between the Kerdi and the tub? Thanks.
I don’t have a link, at the moment, but if you look through my Twitter feed I posted about this just in the last two weeks.
Schluter has a new product designed for this exact thing.
Otherwise you can try to use Kerdi band and Kerdi fix and see if you can seal things up that way.
Peggy Kohus says
Help! Menards sold me a drop in whirlpool tub because I did not want an apron but it is to fit in a five foot alcove. So now tilers are saying there’s no way to fit the tile and flange on a drop in edge. Can you help?
Thanks for all of your posts and awesome information! It has proven to be most helpful with our DIY tile job!
Finally started ripping into the tub surround. I expected a thin flange so I was planning on furring out the studs and dropping the wallboard past the flange. If I was wrong and the flange was thick, I just do any of the methods above. Naturally, my bathroom is plan C so it’s a thin flange but the flange is on top of the old wedi board.
Looks like I’ll be using one of the above sealing methods because it’s about 1/2″ out but do you have any suggestions for filling the space behind the flange? It’s holding steady now but it’ll probably be loose once all the walls come out. I could add wooden shims but I can’t nail them down through the flange. Trying to squeeze cement board between the studs and tub flange to replicate the current arrangement seems like a bad idea.
I think sistering to the studs would be the way to fix it. If I understand correctly, the issue is that the flange is about 1/2″ away from the studs?
If so, you can screw a new stud directly into the stud that’s already there- only it would stick out about 1/2 inch further than the existing stud.
This is a good way to fix walls and if you do this start with each corner and once you get the corner studs plumb and straight you can put a straight edge across them and fill in the middle studs. The middle studs would sit right up to the straight edge and then your whole wall would be straight and ready to tile.
Hopefully, that makes sense. Let me know if I’ve misunderstood the question.
edit: also you could install plywood over the back maybe? that doesn’t straighten out studs though.
The issue that I’m worried about is that the tub is ~1/2″ from the studs all around because they installed it over the wedi panels. The panels came out and now there’s a thin strip of foam and wedi glue wedged between the flange and the studs. It seems pretty sturdy so I guess I could just leave it but that doesn’t seem right.
Info about getting the studs straight is good too, I’ll have to do that next. Thank you.
Ok, I re-read my new post and it doesn’t really clarify anything. I’m worried about the gap between the flange and the studs. Keeping the tub firmly in place is the issue and how to anchor the new supports, not joining the wallboard to the flange. Sorry.
I understand now and I agree that if the Wedi board is keeping things in place I would probably just leave it alone. You still may have to shim out the studs but maybe only slightly.
I’ve found drywall shims to work well for this. You may already be aware of these but others reading may not. They are in the drywall section of the hardware store and are cardboard strips. I staple them to the studs and flatten out the walls that way.
But yours is a good example of reading, planning, and preparing only to still run into the unexpected. That’s remodeling and that’s life. :-)
Certainly can’t argue with the last comment and thank you for all your help.
The framing is actually kind of a mess. There’s a bunch of random blocking that needs to be re-done and the studs themselves are kind of a mess. My tentative plan is to sister the studs out by 1/2″ on the side walls. This will take the wall board past the tub flange. The sisters will be cut in at the bottom so I can attach the tub flange to them. The back wall is up against the flange so that will get shimmed and spaced out with plywood. Does that sound reasonable?
Also, if you space out with plywood, do you need to use longer screws for the wallboard?
I think it sounds reasonable. With using plywood for the back I don’t think you would need longer screws. If anything, shorter might be preferable because I think you can just screw into the plywood. 1 1/4 inch screws are the shortest that I’ve seen for cement board screws though.
I don’t think them passing through the plywood is an issue unless there’s something behind that you don’t want them to hit. Taking photos and mapping out anything important is a good idea.
Oh, you mean putting up whole sheets of plywood like sheathing a house exterior? I meant just put strips of plywood over the studs to space them out. I just looked at that wall and the studs are pretty uneven. I may actually have to put shims under the plywood strips (or sheets).
You could just put up 1/2 inch strips and that would save on the plywood. But, in that case, I think you would want longer screws to get into the stud as opposed to just the ply.
And I definitely recommend the drywall shims. The flatter you get the wall now the easier it will go later.
Not so much a question as just sharing relevant experience. Just finished cleaning up the rim and flange on my americast enamel steel tub. The foam board was behind the flange and tile was set over it. They originally grouted the tub/tile joint but I had ground it out and put in silicone instead. So it was coated with a combination of silicone caulk, wedi glue, grout, and thinset. (I think it’s wedi glue, it’s blue and I think the foam board was wedi board.)
The mortar/grout tag-team had to be removed with a combination of razor blade, wooden scraper, and scotch-brite pad. Couldn’t quite tell which was the grout and which the mortar but I think the mortar formed thick caked on lumps that had to be broken up with a hammer and punch in places.
The wedi glue pretty much came off by rubbing it with your finger. The silicone on the other hand was a real champ: it had to be softened with paint thinner then scraped then the residue rubbed off with the scotch-brite pad.
I don’t know for sure if that means the silicone is going to form a better seal than the wedi glue but it’s definitely more tenacious. I’ll definitely use silicone sealant rather than the Wedi based on this experience.
Good feedback and that’s why silicone is so much better than the easier-to-install acrylic caulks that many people prefer.
But it’s not all about adhesion either. How much a product stretches and how big of a space it can fill is something that comes into play also. Additionally, Wedi glue is a light gray color. Not sure what the blue color would be.
But thanks for sharing your testing and I’m always interested in real-world results.
It’s a light gray with a blue tinge. I keep thinking it’s blue because there was blue foam stuck in it.
Dino Morelli says
Hi Tile Guy,
Looking for some advice for my tile install. I am conflicted about which Ditra product to use. I am planning on installing a 12×24 9mm ceramic tile but would like to end up flush with the 3/4″ hardwood. The Schluter website says to use XL for perfect transitions to hardwood, but that is with 7mm tile. With either approach, what would you recommend as far as trowel sizes? Ditra thickness?
I am doing remodel of my bathroom. The questions is which tile end giving more kodern look, the bullnose or the schluter? Thank you!
Metal profiles are more of a modern, minimal look.
You’re kind of in that in between area but the 1/4 inch Ditra XL if probably still the better choice.
However, if you have a hump in the floor, especially in front of the door, then you would probably be better to flatten the floor and use standard 1/8 inch Ditra.
For trowel size, a 1/4 x 1/2 inch or 1/2 x 1/2 would be the sizes that I would use.
Great, thanks for your insight, much appreciated!
Richard Hadley says
Tile guy nice site for information on tile issues. Great job. Rick from Chicago area. Redoing small full bathroom completely down to studs and subflooring. What are your thoughts on Ditra heat underlayment?
On Kirdi board or WEDI board which do you prefer?
Have you ever installed a Kohler castiron showerpan Selient? Concerns about the flanges on alcoves if you look up details on flange you’ll see what I mean. What do you think about marble honed tumbled in shower? I see alot of people say they would never do natural stone ever again in shower area. The regular sealing maintenance is a concern for me But love the real look of Queen Beige honed marble. Thank you. Rick.
I like Ditra Heat underlayment and have a post on it with a couple of tips. https://www.diytileguy.com/ditra-heat-mat-installation-ignore-rules/
My personal preference between the two is for Wedi board but have no issues with Kerdi Board. Either is fine.
I’ve tiled over a Kohler pan before but it was quite a while ago. The Kohler instructions show that they want the walls furred out so backer board drop down past the flange. If that works for you then that’s the way to do it. If you have tile that aren’t very small then I don’t see why it wouldn’t work to put the backer board above the flange.
I do not recommend natural stone in a shower- especially over the more modern “bonded” waterproofing membranes. I’ve seen too many darkening and staining issues. Porcelain tile doesn’t have the same issues and is much easier to maintain. However, some people are set on natural stone and there’s no talking them out of it.
Have you had to set and level a tub? I’ve got an american standard americast tub (enameled metal with foam backing, looks like). The instructions say to set it on a rectangular area of silicone bead but I can’t find regular silicone in larger tubes and it would take 4-5 10 oz tubes to get enough. Instructions also say a mortar bed is acceptable so I was going to put down 1/4″ of flexbond and set it in that. It doesn’t seem to need much leveling, I test fit it and there was only 1/8″ height difference front-to-back and 1/8″ end-to-end so this is mostly to keep it steady. Any advice?
I hire plumbers for installing tubs so I don’t have any hands-on experience but I’ve never seen one set with silicone. I can’t even figure how that would work.
Mortar is generally used to level them out. thinset isn’t really the right thing and I think you’ll need more than 1/4 inch. But you don’t need tons of it and a stiffer consistency is what you want. You want to set the tub, level it, secure it, and leave it alone until the mortar cures.
That’s about all I know. 1/8 inch is a pretty good starting point. Most tubs need more leveling than that so I think you’re in good shape with just a little bit of adjustment.
I think the silicone in the instructions is just there to keep it steady, dampen any movement, and fill gaps. It’s just a 1/4″ bead under the ~1.5’x4′ waffle-pattern “foot” of the tub that sits flat on the floor. I figured the thinset would serve a similar function. When I took it out, it was sitting on top of the edge of the old mud bed floor, a stringer on the back wall and a composite decking plank down the center. I replaced some of the bad subfloor planks and put down 1/2″ plywood below it.
How level is it expected to be? I thought 1/8″ out of level might be good enough. I was hoping to avoid having to shim up the apron but if thats’ what I have to do…
1/8 inch is workable but the better that you can get it the easier it will go.
I worry that I come across as argumentative. If I do it’s not intentional. I always appreciate your answers. I, and a lot of other people, would be up the crick without your help. Thank you.
Brad Bromich says
I have a Sioux Chief tile shower drain. We had a clog and instead of the water backing up into the shower, It backed up as high as the flange and went over the flange and under the pan liner and leaked out onto the subfloor and through to the basement. Is that supposed to happen?
It doesn’t come across that way at all. You are one of the more active members of this community and your questions help others. I appreciate your contributions and willingness to participate.
No, that’s not supposed to happen.
If the shower contained the water then the water should evacuate down the drain. If it gets under the liner then it could be that the bottom of the shower liner isn’t sealed to the drain flange.
If this happens when water backs up then this is probably the cause. The underside of the shower liner is supposed to be sealed to the top of the drain flange.
I’ve got a gap under the front apron of the tub. It’s higher in the middle and sits on the ends. Not sure if it’s bent somehow or if it’s normal for american standard americast tubs. I was going to put shims under it to get it overly level and support the front. They’re pretty thin at the ends but close to a quarter inch thick in the middle. I’ll do the Ditra/Kerdi-Band/Kerdi-Fix waterproofing at the base of the tub. Is the Kerdi-fix strong enough to fill and hold up the gap under the apron or is it too soft? The bottom of the tub will be sitting on mortar.
As long as the tub is supported by mortar I don’t think a gap is an issue. The apron is simply cosmetic and you don’t want that supporting the tub. That’s my understanding anyway.
I don’t think Kerdifix will support the gap but it will fill it in and seal it. If you want something to fill and support I think a spray foam product might work better for that.
If you are tiling the floor then the tile should hide the gap at the bottom of the tub.
Time to get the studs straight in the walls around the tub. I want to get advice so I don’t start on something over-elaborate and pointless. I’ve been asking about this here on and off for months but I want to get a good plan now that this is the next step in the renovation. The situation is the house is 70 years old, the bathroom started out with mud walls on metal lath, and the studs are all out of whack. It was plaster on purple board and foam board by the time I got to it but the tiles were smaller and not all that straight. The studs are as much as 1/2″ out of plane, crooked, curved, twisted, and I need to shim them out about 1/2″ to come out past the tub flange.
I already did the wall at the faucet end of the tub by sistering most of the studs. A few were shimmed with thin planks I ripped to proper thickness on a table saw. This wasn’t too bad and I’d do a better job if I had to do it again but it took a lot of planing and some of the studs will need shimming with cardboard shims. I think I’d like to go another way for the other two walls. The short wall along the long edge of the tub is exterior and the space is better used for insulation (which is already in place). There’s also a window in it so the structure is complicated.
There’s a few ways I’m considering. Covering the whole thing in plywood then attaching the CBU to that as you suggested sounds pretty good but I would want to shim out the studs to keep it flat. Can I put up shims at regular intervals like 12″ then attach the plywood at these points? Can I do the same for narrow strips just along the studs? My next best idea was to trace the contour of the stud bow on a straight-edged 2x, cut it out, and screw it to the stud. Would it be a bad idea to put furring horizontally across the studs and attach cement board and drywall to those? I could just uniformly shim out the studs with plywood, attach CBU over the crooked shimmed-out studs, and rely on planitop but that doesn’t seem structurally sound; a lot of bend in the CBU and a lot of patch.
You’re not just about to put up a post on flattening out walls, are you? I would appreciate any tips. I can take pics if you want illustrations, hopefully not under “what not to do.”
Hi Paul, of all the things that you mentioned the only one I really like is the horizontal cross-blocking option but the cross blocks would have to be 16 inches on center at a maximum.
But if you can get the bottom flat across then do the same across the top this would allow you to simply put a straight edge on both of these points and bring the center cross blocks out to the straight edge. This would keep everything flat and inline with each other.
Otherwise, sistering is a good way of doing it but I understand that you would rather have insulation in there. Also, planing and shimming can work but it sounds like your existing framing is pretty uneven.
I don’t have plans for a wall flattening post in the near future. I did do some filming for one before my GoBoard post but it has some gaps and missing segments so it will have to be revisited down the road.
When I mentioned that horizontal option, I meant lay 1×3’s or something similar perpendicularly across the faces of the studs similar to what they do for ceilings around here, not add horizontal blocking between studs and attaching to those. The cross-blocking is an option as well but seems like if I’ve got room to do that I may as well sister and plane. Flat furring across stud faces doesn’t give me a lot over just putting it up vertical along the stud as a shim other than that it’s flatter because it doesn’t pick up the twist of a warped stud. It’s also a bit easier to add shimming behind it if there’s insulation in the wall.
How much is it safe to bend a sheet of permabase CBU to put it up over warped studs? If I ever find a place that sells planitop around here, I may just have to rely on that to flatten things out.
Too bad about the post. Can’t complain with all the helpful information you already have here. Thank you!
If you have cement board mounted horizontally above the tub and overlapping the tub flange, do you try to avoid having a tapered edge at the bottom? Sounds like a choice between a flat edge or an edge that’s less likely to crumble.
I much prefer the tapered edge. Not really sure why but crumbling would certainly be a factor.
Could you please recommend specific brands and types of sealants that you use? There’s kerdi-fix and wedi glue but are there any particular silicone or urethane sealants that you use?
Typically, I use Wedi sealant as I always have it on hand. I usually use color matching silicone that matches the grout.
Sometimes I will buy generic white 100% silicone rather than the “color matching” version. Usually, this is either DAP brand, Premier Xtrabond, or the newer Gorilla brand. I usually stay away from GE 100% silicone but that’s based more on 2nd hand rumor than my actual experience.
Bostik Ultraset is one of the best urethane’s around (my opinion) and it’s really expensive. But it’s one of those “if you can’t do it with “X” then it can’t be done” products.
Lastly, if you are looking for alternatives to Wedi or Kerdi sealant you could always consult the GoBoard Alternative Sealants list. Sika has a good reputation and I know one industry person that speaks very highly of OSI Quad Max- both listed on the GoBoard list.
Thank you, that is very helpful. The substitute sealant sheet is great. Do you have an opinion on MS polymer vs straight polyurethane?
I looked up Bostik ultraset and it looks like it’s a waterproofing membrane that comes in a bucket. Did you mean Bostik 915 or did they change it?
I started on this because I was looking at sika and noticed that they don’t recommend it for vinyl surfaces so I can’t use it to seal redgarded CBU to the vinyl window. Would be nice to use the same stuff to seal the gap between CBU and both tub and window frame (not to mention substitute for Kerdi-fix to seal ditra to the tub).
I don’t have anything intelligent to add to MS polymer vs polyurethane. I don’t know enough about the chemistry.
Ultra set comes in a sausage tube and it’s fantastic tenacious stuff. But probably not what you are looking for.
Didn’t know that about Sika. I don’t use their products all that often as I usually have something else on hand but it’s good to remember.
In case you’re interested: I emailed Schluter tech support and asked if kerdi-fix can be used to seal surround to a vinyl window. They said that a) it adheres to vinyl (good to know) and b) can be used in wet areas (I sure hope so) but c) I should contact a regional representative to get help with my specific application.
I’m glad to hear this because I’ve used it for that very purpose before. :-)
I would like to know what needs to take place to tile on a concrete wall. My contractor says Redguard should be sufficient but there is a large gap on the side of the tub between the concrete wall and the tub. What should he fill it with and how do you make that area waterproof before tiling? Also, he placed hardiebacker over the two sides that had drywall I read that it should be attached directly to the studs instead and that drywall should be removed.. My biggest concern is the waterproofing because I’m on the 10th floor of a building. Thank you in advance.
I’m glad that you mentinoned that you live in a condo because that makes a difference. The drywall that the contractor fastened Hardibacker to is quite likely a fulfilling a sound and/or fire requirement for the multifamily dwelling. However, they do make longer screws and the panels should still be fastened to the studs.
As far as the concrete wall, I’m a little bit afraid to speculate on the situation. It’s important in multifamily dwellings to understand the reasons behind the building components. My guess would be that this would be a good place for a waterproof foam board. But it’s hard to say without inspecting the inside of the unit.
So there’s nothing wrong with questioning the contractor’s reasons for doing things but it’s probably advisable to consult with someone that has more knowledge about your particular building.
I have an older home that has a cast iron tub with a flange. The walls are tiled and have a cement board with green board behind it. I recently removed the caulking that was between the tile and tub and noticed that water is seeping behind the caulk and tub flange. Since tile and grout is not completely waterproof and cement board will absorb some water wouldn’t caulking between the tile and tub trap that water and eventually find its way out (usually not where you want it to)?
You bring up a good point about there’s merit to it.
Some people have reasoned this way decided to leave that joint unfinished. Alternatively, some leave weep holes to let water escape.
But as a contractor, if I leave that joint with holes I will be guaranteed to have to “repair” it.
If it’s your own home I don’t see anything structurally wrong with leaving it with voids. But it may not be fun to clean.
Jim Kart says
Hello, there is a piece of wet/soft drywall just adjacent to the end of the bathtub which is opposite to the shower header. A few months ago, I have a contractor replaced that piece of wet drywall. And I caulked around the tub, and small window with a small wood deck/platform just right above the shoulder when standing inside the tub – thought the water may splash to the platform and traveled to the bottom. Since then the situation didn’t improve. the new drywall in particular the area meet to the tub from floor to tub surface are wet again. I cut a small hole on the caulk along that vertical edge where the tub meet the drywall, and saw the water came out.
Was the shower water seeped to the lip area from the bottom caulk and then travelled laterally out and wet the dry wall adjacent to the tub. I checked the tile grout. everything looks fine. This issue is sitting there for a long time now and really bother me. What can I do to fix the problem? Many thanks for any suggestion.
You have to try to track down how water is getting in. Could be the window or a hole in the grout or caulk somewhere.
Also, water can shoot around the perimeter around the tub so if water gets in anywhere it can shoot around to the side that is getting wet.
Thank you for all the great information and help you’ve provided with your site. I’d like your suggestion for filling the void between the tile and the tub flange. We’re in the middle of remodeling the bathroom and removed the single-piece tub surround and have now had to sister all the studs of the three wall alcove to have the 1/2″ goboard backer meet the existing walls that were about 3/4″ out (5/8″ plus tar shingles they used to meet the old surround flange.
Installed is an acrylic-fiberglass soaker alcove tub with flange on three sides.
So, now I’ve got one wall with goboard approx. 1/2-3/8″ extended out from the inner edge of the tub flange. I can seal the 1/8″ space between the flange and the bottom of the goboard with the urethane (goboard brand) sealant as well as coat the bottom of the goboard for good measure. But what to do with the 1/2-3/8″ gap between where the back of the tile and the flange meet? I read earlier here in the comments that putting a backer rod would be one way, but can you offer any other suggestions to help back that bottom edge of the tile?
Is the backer rod too flexible being its styrofoam? I’m hoping to be successful using 10″X14″ tile so more than 80% of the tile will be thinset to the goboard above the tub deck.
Further, I was thinking I would also seal in “gap-filler” to the flange before tiling over, is that a good idea?
Finally, I thought it best to bring the tile down to about 1/8″ from the deck. Initially I was thinking to fill in that 1/8″ gap between the tile and tub deck with 100% silicone. I could use more of the urethane sealant instead? What do you suggest?
Though the tub is level, on a mortar base, has stringers for the edges, and roofing nails into the studs holding down the flange edge, I still presume there will be some flexing as its a acrylic-fiberglass and a filled tub with a person in it, plus changes in room temps for the MN seasons will all attribute.
Thank you VERY MUCH for hopefully understanding and suggestion to the above. I’m also hopeful this reaches you soon as I am in the middle of the project.
Best regards and much success!
I forgot to add, the distance from the bottom of the tile backer to the deck of the tub is about 1.25-1.5″ for which the tile needs to cover.
One way to handle it is to notch the back of GoBoard so that it fits over the flange so that you still have something to adhere to. This is probably the best way to handle it.
What I did in my video is use sealant and mesh tape over that whole section. That will fill in some of the gap. Then I just filled any void with mortar.
I’m not sure how “by-the-book” that is but in not sure that there is an industry accepted practice either.
But definitely have a gap between tile and tub. I would use urethane as a finished seal. I think silicone will look better.
Thanks for the fast reply and suggestions. Well, I realized this after I had fastened the goboard, and learned a lesson. Instead of taking out the goboard and notching the back and rearranging things, I took extra leftover stock of the go board and sealed that in to make up for the backside gap. Thanks again, keep up the great content, its a help to a lot of us.
I guess that would work if it’s sealed to the board above it.
Definitely not plan A but a means to an end. ?
Yes, I sealed it in well and it set nicely. Plan B worked, thankfully.
Fred Sager says
Good afternoon TILEGUY. I have read your information on sealing the gap between the top of the tub flange and bottom of wall board. I have questioned all the manufacturers whose products I have used to complete my tub-to-shower conversion, and all seem to either offer no solutions or are non-committal about their products. My first question/concern pertains to WEDI JOINT SEALANT; is this the same as WEDI GLUE that you mentioned in your posting? I hope so, because I already purchased the WEDI JOINT SEALANT. I have installed a shower base made/sold by ONYX COLLECTION, and I have installed half inch HARDI BACKER BOARD to all three alcove walls where the original tub was removed. ONYX specified to leave a 1/8th inch expansion/contraction gap between the top of their shower pan flange and the bottom of the HARDI BACKER BOIARD. DONE THAT! ONYX also recommended to fill that gap above their shower pan with 100% silicone. I do not want to use silicone in that gap because OVER TIME IT WILL MOLD. I want to use the WEDI JOINT SEALANT because WEDI says it is MOLD/MILDEW PROOF, but WEDI also says it is not to be used as a gap/joint filler. I ask my second question to you….can I successfully put this WEDI JOINT SEALANT in the gap between my ONYX shower base and HARDI BACKER BOARD to prevent water from going through that gap? My last question concerns liquid water-proofing products such as REDGARD. I have talked to the company that makes REDGARD and also WEDI. Both give me inconclusive info about products that will BOND to their products. I DO know by researching each that THINSET will bond to WEDI JOINT SEALANT, and REDGARD will bond to THINSET, so I GUESS that a good THINSET will be the only way to proceed, IF the WEDI JOINT SEALANT will actually adhere to my shower base and backer board and prevent water seepage ??????????
I have many concerns. Please comment and all help will be appreciated. THANK YOU.
If the instructions for the product say to use 100% silicone then that is the way to proceed. 100% silicone doesn’t mold. You have to make sure it actually says 100% silicone on the tube and doesn’t say anything like acrylic, paintable, or cleans up with water.
Myself, I would have no issues with using Wedi joint sealant (aka “glue”) in that joint. But if Wedi doesn’t ok it for that use and your shower manufacturer wants a different product then why not use the other product?
So here’s the order:
1. Shower pan installed
2. hardibacker installed with gap above the pan
3. Redgard over hardibacker
4. 100% silicone in the gap (with backer rod. Read my silicone caulking post if you’re not familiar with this product)
5. Tile installed with modified thinset mortar
Fred Sager says
Thanks TILEGUY. I just wanted to make sure that all the different components were bonded together properly. I didn’t want to have leaks that would require a TEAR OUT and REDO.
I totally understand wanting to get it right the first time! ?
Reg Simard says
Hi, good morning. Love your videos. Well executed, a lot less “show” and a lot more “go”. Lots of very good info. Quick question, and I will try to keep it as short as possible….. I do the opposite of everyone else. I/we, okay my wife wanted to convert our walk in shower to a tub (jet and air). I’m a carpenter/cabinet maker, so pretty darn handy …. Anyway the existing was only four years old, so I figured, at the laugh of my contractor buddies, and I do know better, that I could save the bathroom and carefully add the tub. So far, so good. I was able to remove the existing wall tiles and save them. They are spot applied with thin set (nice globs) to DensShield. After demolition it was nice to see absolutely no water penetration/damage. I think the walls benefit from the added air space between the porcelain tiles and the DensShield because of the spot bonding with the thin set. I know a lot of people think this is not a great way to set tile, but from what I see, and the fact that they definitely did not “fall” off of the wall while I was trying to remove them …. Anyway, long story short ….. I will be bonding new ¾” fir ply to the existing 5/8” subfloor when the drain work is done. I will then be laying ……. ¾” rubber sheet (gym floor/horse stall mat) on top of that. I assume that will deaden the floor noise considerably (tub on second floor) then the tub on that. So, the aluminum tile flange on the tub (which they did not tell me was an applied one when I ordered it) will end up just below the edge of the DensShield. Now my question … and I know you have video options for this ….. filling the gap between tub and backer board ? Here is my plan, feel free to laugh …. I plan to add ¼” to 3/8” spacers on the studs at flange area, so as to bring the front of the tile flange just back approx.. 1/8” from the front edge of the DensShield, (by the way, the tub manufacturer, Oceania in Quebec, is adamant about no mechanical fasteners in or above the tile flange, only silicone to the studs), painters tape the tub, then fill gap and onto the DensShield with Kerdi Fix, then apply Kerdi tape and smooth out…… after drying RedGard as much as possible …. Thin set and tile …. Voila! I spared you the other one hundred steps like having to change the mixer set, insulate, etc. etc. Anyway, if you can decipher any of this and have a second to respond it would be much appreciated to have a second opinion ……… Wish I could have attached photo’s ……
I think it sounds OK. However, I don’t recommend spot bonding and would encourage you to use a notch trowel and aim for 100% coverage.
Otherwise, I don’t see a problem!
Thank you. A second opinion is always valuable.
So many ways do things. Sorry if basically same questions asked by others. I’m stuck in analysis paralysis after reading all options for quite some time. My space for tub/shower is 1.25″ too wide. Have purchased 1/2″ USG Ultralight Foam Tile backer Board, sealant & membrane. Space adjustment issues result from need furr out wall aprox 1.25″ causing vanity/door spacing & toilet rough problems. Original plan was to furr out so that the foamboard notched or lays over the flange edge. Just seemed like bit more waterproof if front plane in front of the flange.. However, if I shift tub so that face of the foam board is flush inside edge of the flange on both ends I’m off only .25″ which could be brought out with plywood or other “furring material” in strips or sheet. My particular tub instructions state to screw through flanges to studs specified intervals.
Options seem to be
1) Furr out 1.25″ the plumbing side (unfortunately no room other wall due to doorway).
2) Shift tub so board panels flush with inside tub flange (resulting only need furr out wall aprox 1/4″-1/2″. or possibly small notch over flange.
3) Furr out only the tub area which would result in aprox 1-1.25″ plane difference rest of bathroom wall. (Bath is basically 5×8 so every inch counts.
My dilemma is Delta has specific sealant warnings & recommendations for the tub. It states “Silicone & acrylic latex sealant are not recommended due to potential adhesion & shrinkage, which could lead to leaks. For best results, use an advanced kitchen & bath polymer sealant such as DAP 300, Red Devil RD3000, Eco-bond.”
If the foam board is notched to any degree to go over the tub flange (is there a minimum thickness that should be in front of the flange?) is it just a sealant under so water can’t go up & overflange or can a membrane & sealant or ? still be used? With acrylic tubs just seems always possibility movement & that seam busting open. New construction so can do this any way necessary but hoping good solution without having give up too much of my bath space (& resolving other resulting issues) to furring whole wall. Guess, another question…is there a way to nicely transition (without looking to hokey to use a technical term) if say the tub area is furred out but the remaining wall is not? 1-1.25″ plane difference? Note: this is to be more of a cottage/rustic appearance cabin..
My curved tub with apron has the same thick flange down front edges so same issue applies sealing that area.
Last thing I want is leaks (I’m overkill in preventing those everywhere). Not sure if logic same as practice but having waterproofing in front of potential leak better than behind? Is sealant plus membrane or mesh as strong seal as overlap of the board?
Which would you do or something else you would recommend?
Thanks so much! Great website by the way.
No matter what, the backer board and waterproofing need to hang over the inside of the tub flange so that water will fall inside the tub rather than behind it.
Personally, I like the idea of just sliding the tub all the way to one side and building a corner that is 1.25 inches (+/-) on the other end. Preferably, this would be the non-plumbing side so that the plumbing doesn’t have to be moved but it doesn’t sound like that’s the case.
If you can split a bunch of differences and make it so that water is managed properly then that will work too. I just think the amount of space is a bit too much to overcome.
Thanks so much. I agree with waterproof layer to run inside tub (not behind!). Sorry additional question(s) help resolve in my mind.
The Goboard video looked like you put the board flush with the inside tub flange & sealed & taped the joint. Is that type joint as strong as the board complete overhang or notched to overhang (blocking behind that area in any case)..
Seems like that would be in effect be a continuous one surface water layer with the board flush inside & sealant in gap plus sealant &membrane/fabric. Is that acceptable & is risk any greater than overhang with sealant in that overhang to flange space?
Maybe, answering own question but analyzing worst case potential risks of methods. If flush seam (what appears in goboard video if I looking at it correctly) busts loose water could easily go through that gap (only protection tile & grout). If overhang the board & that seam busts the tile & grout plus tile board still blocking plus the flange height helps keep water out of the wall space. Is this sound reasoning?
Ok so hopefully final question. What is minimum board lip overhang flange to provide adequate strength if notch the board? Asking as have similar situation in other bath shower space (fortunately no complicating issues there). Long gone fired builder took rough in opening sizes & added to them (you should have seen window door openings! Fun times!
Thanks again for all the great help this site provides.
How flush the board is with the tub flange is more of a matter of circumstance than anything. You are correct that one side of the tub is flush in my GoBoard video. However, on the other two sides, it hangs over significantly. It’ just a matter of how the tub was positioned in the space. Some tubs have a much thicker flange- like 3/8 inch which will result in a more even installation. So there’s no correct way but rather a matter of working with what you have.
As far as notching, I’m not aware of an official statement on this from the people at GoBoard. I know they make GoBoard in 1/4 inch thickness so maybe that would be OK? That’s just speculation on my part.
With method #3 (or even method #2) , how do you deal with screws going through the flange on acrylic tubs? Delta requires round head or pan head screws and they stick out about 1/8″. Do you stop the mesh tape or banding above the screws? Or somehow adhere it right over the screws?
The screws can’t stick out to the point where they would interfere with the tile. If they do, then something has to be done about them. Either furring the wall out past the round heads or going against the manufacturer’s rules and installing different screws or possibly counter-sinking them might be options?
Assuming the round heads won’t stick out past the backer board and interfere with the tile wall I typically will mesh tape and seal over them. Sometimes care has to be taken to make sure the sealant seals completely around the head.
I’m still at it…
I mentioned above that the bottom of the tub apron was curled above now I’m trying to figure out how to tie the ditra to it correctly. The tub is mounted on top of 1/2″ plywood and the floor in front of it is 3/4″ plywood (so it sits 1/4″ higher) with a 1/8″ expansion gap in between. This was done on purpose so ditra would get above the gap but it’s not quite enough. The gap between the taller plywood and the tub is 1/4″ to 1/8″ at the edges of the apron but as big as 1/2″ in the middle. So that gap is 1/2″ wide and 1/4″ deep throughout the center portion, not including the 1/8″ gap between the 2 plywood sheets, which seems too big to fill with sealant to keep the ditra supported.
Do you have any advice on how I could handle this? Wish I just put in a freestanding tub. Thank you.
I almost think an expanding foam might work best? As long as the tile on the floor ends up covering the gap. Might be a little tricky keeping the foam out of the waffles unless you prefill the Ditra and tape everything off.
The ditra isn’t down yet. It’s just the two levels of plywood and the tub. I want to put something in that gap that will support the Ditra but not cause excessive movement so the seal between ditra and the tub breaks down.
Thought of putting sill gasket in the plywood expansion gap and along the tub and filling the rest with the same floor patch that I’m using to level the floor. Or cut a strip of 1/4″ plywood to fill the gap and maybe glue it to the side of the taller sheet. The foam sounds like a good solution but would it bulge up if the plywood moved? What kind of foam would you use?
Thank you for your help.
So it looks like I misunderstood the situation a little bit. But the sill seal and floor patch, like Planipatch, would be the way to do it, I would think. Then you can cut the sill seal off with a razor knife after everything has dried.
You said in your tub flange sealing instructional: “The reason that I don’t recommend the mesh tape with step one (silicone) is that the silicone will act as a bond breaker to thinset if it’s smeared over the surface.”
This really has me confused because I am planning to use GoBoard and I watched your installation video and you appeared to be sealing all seams with a silicone caulk. I am just about to install my GoBoard and i don’t want to put a caulk on the seams and spread it out a inch or so on each side of the seam if it may act as a bond breaker to the thinset. What I have purchased (not used yet) is a product called OSI Quad Max. PLEASE steer me in the right direction so I don’t put tile over something it may not bond to.
GoBoard sealant isn’t 100% silicone caulk. They are two different products. It’s ok to install over the sealant.
The long end (60″) of my tub flange is not straight. I put a 1/8″ spacer in the middle but I have close to 1/4″ gap on each end. Sort of a mild banana shape. Do I need to cut a u shape in my Goboard so that I have no more than an 1/8″ at every point or can I put extra sealant and mesh tape over those areas to insure a good waterproof seal?
Sorry for all the questions Tile Guy but this is my first tile job and I want to get it right. I plan to use 12X24 wall tile and I purchased a thinset product at Menards call TEC 383. It’s a polymer modified, ultimate large tile mortar. I’ll be laying my tile over prepared Goboard. Also, would you recommend a 1/2″ X 1/2″ trowel?
Am I on the right track or would you recommend something else? I’ve read a lot of your material and watched a couple video which have helped very much. Thank you for providing this for us DYI’ers.
Probably the proper answer is to cut it to fit but I think the sealant will work just fine in a 1/4 inch gap
Sounds good to me! Don’t hesitate to ask questions. If you are wondering then others probably are too.
Christine Grant says
I’ve tiled floors but I’ve never tiled tub-surround walls. I understand most of the details I’ve been
reading on your website but I don’t understand the purpose behind some of the details. I thought the idea was to isolate the tub from the tiled walls so the tile field doesn’t crack when the bath tub flexes. Is that not the reason for the 1/8″ gap filled with flexible caulk/silicone between tub deck and tiles? But it seems from what I’m reading that I’m actually supposed to attach the backerboard to the bathtub flange (as per your “three methods”). If the two surfaces are connected, won’t it cause cracks in the grout/tiles if the tub shifts?
I’m planning on using 1″ strips of leftover Ditra underlayment to fur out and the tub flange so that it’s flush with the backer board, securing it with mesh tape, Kerdi membrane and thinset. My tiles will be finished at top, sides and bottom with Schluter tile edge (Schiene basic). I planned on putting a bead of caulk (silicone?) between the bottom Schluter strip and the bathtub to isolate the backerboard/tiles from the tub. But it seems the main concern is waterproofing not separation of the two elements??? Do I not have to be concerned with keeping the tiled backer board separate from the bathtub?
Could you just outline the basic principles for me? Thanks so much for all your comments and advice.
Things can move a bit and that’s OK. The reason for flexible sealant vs a mortar is that the sealant allows for the movement.
You didn’t specifically mention this but I’m assuming you are using Kerdi membrane over your whole tub surround walls? The Kerdi helps absorb the different movements between the tile and the tub/wall board.
I don’t know if that helps.
Thanks so much for your speedy reply. I have tile backer board on the three walls but I was not planning on putting Kerdi Membrane overall. I bought a Kerdi waterproofing band and had planned to fold it into an L-shape with about 1/2″ under the Schiene edging where each of the three walls meets the bathtub, and the rest of the band
(4 1/2″) over the shimmed out tile flange and the bottom of the cement board.
So, working from back to front the order would be tub flange shimmed level with
backer board by strip of Ditra underlayment, mesh tape joining strip of underlayment to backer board, thinset, Kerdiband, more thinset, leg of Shiene tile edging, thinset, and finally tiles.
I plan to run a bead of caulk (silicone?) on the tub deck before putting the metal Schluter strip in position. Thank you, once again, for your invaluable help. Much appreciated!
Hopefully, you are planning on putting some sort of waterproofing membrane over your cement board walls otherwise, it sounds like an OK plan. Good luck!
Is kerdi-fix alone sufficient to seal the 1/4″ gap between the horizontal tub surface and bottom of the wallboard in a tub surround? Flange on the tub is behind the wallboard, the wallboard has liquid waterproofing on it, and there’s foam backer rod at the back of the gap to avoid a 3-sided bond. No mesh tape or kerdi-band.
I believe Kerdi-fix, or similar sealants, are OK for that application.
However, I am warming up to banding, like Kerdi-band, being used for that as my preferred method. Not because sealant alone doesn’t work or that I’ve had any problems with it. But I think it provides a better and wider bonding surface.
Kym Ng says
We have our bathroom redone about 6 months ago. We know our contractor used dry-wall panels specified for the shower/tub area. We have 3/8 inch quartz whole-piece panels all around over the drywall. I have no worries about the area covered by the panels but I worry about the gap between the panels and the tub.
The contractor (with 30 years of experience) thinks the L-shape tub lip and the slightly slanted design will keep the water from going behind the quartz panels. I am not certain if they have done anything to prevent water from sipping through the connection and reach the water-proof (mold resistant) drywall. It seems to me the only thing he did was silicon caulking on the outside.
Now 6 months after, I accidentally found out the other side wall (blocked by some furniture) have a few spots (1-inch to 4-inch diameter) bulging out and they are around the same level of the tub lip. The rest of the drywall did feel slightly wet to touch. So, we suspect a slow leakage that has worked its way through the studs to the other side and reached the drywall.
I then found our caulking between the quartz panel and the tub has a slight gap. After a shower, I dried the area completely, I stuck a paper towel next to the gap and water oozed out right away and soaked up the whole paper towel.
Do you have any advice on what to do to plug the gap between the very small gap before reapplying new caulking?
It sounds to me like your shower was built incorrectly and the best thing to do would be to have the contractor redo it before more time passes. In general, you never want to rely on tile (or quartz panels, in this case) and silicone for your waterproofing. There should always be a primary waterproofing system behind the finished product.
But, to answer your question, I’m not sure what you would use to plug the gap other than more sealant.
I have to be honest, out of all the blogs I’ve read in tub surrounds, yours has been the most helpful.
Couple of questions in hopes that you might be able to help a DIYer.
I had the tub installed but the guys never put the screws in the tub that I noticed you had in your pictures. Is this something that’s necessary?
For the gaps in between the durock, I pretty much butted mine up to one another. Should I take it all down and put a 1/4 inch gap in between them?
Lastly, I brought the durock over the flange on 2 sides and put silicone underneath. On side 3, because of the wall set up, I had to bring the durock above the flange and then silicones. Is this ok to have the two sides different? Also, I have not red-guarded yet and already put silicone in some gaps. I’m guessing this was a mistake too.
I’m strongly debating taking it all down and redoing it.
Lot of pressure lol but I know I can handle it with the right guidance.
Hope you can help and thank you in advanced.
If you are installing Durock cement board, and not foam board, then you don’t have to gap the boards, especially not 1/4 inch. Also, I wouldn’t worry about the two sides being different. As long as the Durock sits past the flange so that water will run down into the tub and not behind it then you’ll be OK.
It’s best to Redgard before silicone but it’s not the end of the world if you do it the other way. But you might have some issues with it sticking where the Redgard meets the silicone.
I’m pretty sure the tub is supposed to be secured to the studs. If it’s a steel tub, a lot of times I just see roofing nails installed on top of the flange. Fiberglass is usually drilled through and screwed. You can always look your exact tub up and see how they want it installed.
Thanks for your comments!
Jim. I says
Thank you for sharing your expertise. I am using 1/2″ cement board on the walls hopefully doing everything correct. I am new to tiling and see there is much concern over the cementboard-shower flange interface. My question is this. Can I stop the 1/2″ board about a foot above the flange and use two 1/4 inch board to finish this section? The first 1/4″ board stopping 1/8″ above the flange and the second 1/4″ board extending over the flange an 1″-2″ or so. It’s extra work and time and I’m not sure if this is even a feasible idea or not. What do you think? Thank you again for your generosity in time and expertise. It is very much appreciated.
katherine crumpler says
I am a homeowner who hired a guy to install a tile surround around my tub. It looks ok….but I noticed the tile does NOT cover the tub flange! Is there any good way to seal this, short of tearing off all the tile? He became very defensive when I pointed this problem out to him.
Not only should the tile cover the tub flange but the backer board and waterproofing should also.
But make sure that you understand where the flange is. Tubs vary and I’ve seen some weird situations before where it might look like a flange but it isn’t the real flange.
Hey DIY Tile Guy,
I got my hands on some Wedi Sealent.
I have the Durock installed already and can use the Wedi or mortar with fiber tape to seal the screw heads and corner gaps.
Do you suggest using wedi in the corner and then thinset over in the corners or just use wedi on the corners with tape (one corner has a 1/4 inch gap I have to fill. Also, I’m going to redguard but I’m unsure if the red guard will cover the Wedi.
What do you think?
I was thinking Mortar on the screw heads and in the corner gap use the wedi with a thin coat of mortar over it and then red guard.
Appreciate your thoughts.
Thanks a lot
I’m not really sure what the application is? If you are using Durock foam board with Wedi Sealant then I would use the Wedi Sealant in place of where you would use the Durock sealant: in the corners, seams, and over the penetrations. But you’d be better off using Durock sealant with their own board, in my opinion.
If you have installed Durock cement board then I wouldn’t use the Wedi sealant at all. I would thinset over the screw heads and thinset and mesh tape all seams and corners then Redgard over that.
If you want to use the Wedi Sealant to seal the tub flange then that’s the only area that I think it could be used.
What waterproof silicone do you recommend that stays flexible but doesn’t shrink? I’m re-Tiling my shower bench (weight bearing). Awesome tutorials by the way.
Anything that says 100% silicone assuming that it is something that will show. If it’s underneath the installation then a urethane is a nice choice.
Have you used R guard or noblesealant 150 before. If so which would you prefer.
My husband installed a new cast iron tub and backer board for the tub surround. He installed the backer board so the tile will sit directly above the tub flange, not the backer board. The backer board face lines up with the back edge of the flange. I am installing the tile and need some advice on how to best protect from water intrusion. I will not be able to overlap the tile over the tub flange; the tile will likely sit slightly proud of the flange–taking into consideration the thinset thickness. Do you have any suggestions?
I’m not sure what R guard is? Short for Redgard? But I’ve used noblesealant 150 before and have found it to be an excellent sealant. But I would advise making sure that you are using the correct sealants with the correct products. Not all sealants and products go together.
I don’t recommend doing it that way. If we assume that tile and grout are not the waterproofing layer, which they are not, then how will the water travel behind the tile? It sounds like it will hit the backer board and go behind the tub. Or absorb into the backer and go behind the tub into the wall.
I don’t think that’s what you want.
Seth H says
I have a contractor that has installed backer board and did not seal it between the tub flange and backer board. I have pictures that better represent my statement. I am hoping that I can get an experts advice on what work I have received and what I need to do in order to remedy the situation. At this point the issues have been covered with tile. The remodel has gone well over a month past our original date. My wife and 2 children are ready to be back in our home but at what cost? This isn’t a flip or a home to sell in the next few years even. We have chosen to remodel to live here for 10 years or so longer. Please help
We have attached kerdi board to the walls setting it near the top of the tub flange just barely in front of it leaving a 3/4″ gap between the tub and the bottom of the kerdi board. Can this be filled in or is the gap too wide?
Probably the best thing to do is to remove the bottom row of tiles and seal the flange area. I’m not sure how it was waterproofed but usually the waterproofing manufacturer will have a method that they prefer. Then install a new row of tile.
It’s too wide. I’d move the board down or maybe cut it differently to eliminate that issue.
Thanks for our excellent articles! I have a new tub installed, with hardiboard walls, coated with Redgard. The flange gap is sealed/bridged with mesh tape and polyurethane adhesive. I am planning on installing 3×6 Datile subway tiles on the walls, but am not sure how to adhere the first course (the layer that abuts the tub), as most of the width of the adhesion area is polyurethane adhesive. Will thinset stick here, or is there a better alternative method?
John Tile says
Thanks for our excellent articles! I have a new tub installed, with hardiboard walls, coated with Redgard. The flange gap is sealed/bridged with mesh tape and polyurethane adhesive. I am planning on installing 3×6 Datile subway tiles on the walls, but am not sure how to adhere the first course (the layer that abuts the tub), as most of the width of the adhesion area is polyurethane adhesive. Will thinset stick here, or is there a better alternative method?
Assuming the right sealant was used the thinset should stick to the sealant. I’ve asked this question before of multiple people and no one seems to think it’s an issue.
Hello, I will be installing a acrylic shower pan with a 2.25″ high flange/lip and its 1/4″ thick, I will be installing 1/2″ durock 1/8″ above it at the bottom, with backer rod and a 100% silicone bead, now how far down do I over lap the first row of tile over the durock on the bottom if any? and do I seal that with another bead of silicone or do I use grout? Also what might be the situation where I would consider notching the studs possibly for my install if at all? Thanks for your time,Wayne
I think the tile should come all of the way down to sit 1/8 inch above the tub. So if you’re using subway tile it gets interesting. If you can seal the tub with a waterproof banding material or with the sealant and tape, as shown, I think you can thinset the tile to that surface. I would be concerned if the tile was only bonded to that surface though. That’s why I think you need a big tile at the bottom so it’s bonded to the backer board as much as possible.
Hi, there. I’m preparing to replace a plastic tub surround with tile. There’s an access panel to the plumbing side of the bathtub. From there, it looks like there’s a 1 1/2′ height of cement or fiber cement backing board that extends above the tub, and then some drywall-type backing above that. The tub (60’s cast iron?) seems to have no flange – the tub curves up from the overflow to a flat edge upon which the backer board rests. (I have a photo that I could email to you if this is hard to visualize.)
If I find that there is indeed no flange when I tear out the front wall, should I install the new concrete backing board so that there is a 1/4″ gap between the board and tub rim that would then be filled with silicone or some other sealant? Or should the board rest on the tub rim as in the previous installation? And if the second option is appropriate, how would one make a waterproof seal between the tub and board?
Sometimes, the old tubs don’t have flanges. If it doesn’t have one, you can do either method that you’ve described. For your application, I prefer the Schluter-style fix with Kerdi-band for waterproofing that is shown in the second option in this post. The embedded video shows how to install Kerdi band on the walls and around the tub. Make sure that you seal the bottom of the band to the tub with Kerdi fix or something like that.
Gapping the cement board above the tub 1/8-1/4 inch would be advisable.
I’m working on my bathroom where I’ve ripped out a faulty fiberglass one piece tub/shower. I’ve got a new steel/porcelain tub in but the flange depth is huge. In order to get kerdi board over it, I’m going to have to shim 1/2″ or more out. I can do that, but then the problem is how to join the kerdi board to the drywall that’s just one stud over and still set back to the original stud depth. I need the kerdi flat for tiling, so I can’t just bend it to meet the drywall. I have the same problem at the horizontal joint at the top of the board, but I’m planning on wet-shimming to adjust for variations in the studs and I presume I can gradually adjust the depth as I go up so that the top (60″) meets the drywall better.
The local shop I ordered my kerdi board from recommended notching the back of the kerdi board so that it doesn’t have to be shimmed forward fully to go over the flange, and to also notch/bevel the vertical edge where it meets drywall. Those two things together would probably help keep that joint mismatch to a minimum, and then the tile (10″H x 20″W) can bridge (and hide) that joint. Is this an appropriate thing to do with kerdi board?
Another idea I’ve had is to just overlap the kerdi onto the drywall and then use an outer corner bullnose all along that edge. I’d rather not go that route since we’d have to find, buy, and set a matching bullnose.
Other ideas? thanks!
If you can set the Kerdi-board on top of the flange then you can use the K-banding technique that is shown in the Schluter video under “Band the Flange.”
However, if the flange is in front of the tub then you have to shim the Kerdi-board out to where it’s at least flush with the flange and then you can band it like above.
As far as blending it with the sheetrock walls, your best bet is probably going to be to put a jog in and treat it as an out-corner like you mentioned at the end. Another option is to re-drywall the entire wall but that’s probably not really an option.
One trick that I’ve used is to shim out the end of the drywall up to 1/8 inch using drywall shims. I cut the screws and tuck them in behind the board. That will buy you 1/8 inch but it may not be enough for what you need.
Good evening, thank you very much for all of this information, I’ve been reading different posts from your site for the last couple of days. Would like to ask one question from an expert. We have just had our americast tub installed by a plumber and now thinking to put the walls (goboard) up. However, there is a 3/4″ gap between the studs and the tub on the plumbing/faucet side (apparently the drain position required the tub to be placed that way). If we put 1/2″ goboard we still need another 1/4″ (at least) to bring the goboard flush with the tub flange, otherwise the board will be behind the tub lip. We can shim the studs and bring them forward but the issue is that if we do that than the transition to the adjacent drywall will be problematic. Goboard will be 1/4′ out compared to drywall, it will not be a smooth transition. What would be your advice how to approach this situation? How to meet the requirement of bringing the goboard flush with the tub flange and at the same time flush with the rest of the drywall? Would really appreciate any solution. Thank you in advance for your reply!
The most important thing is to have GoBoard in front of the tub flange. However, doing this will have a couple of consequences:
1. The wall will have to be shimmed out
2. The faucet and/or tub spout may also have to move forward
3. There will probably need to be an angle on the end of the wall that returns into the drywall
The other options would be to remove the tub and reinstall it so that it’s closer to the wall or remove all of the drywall on the one wall and shim it out so that it’s flush with the new backer board
You probably won’t like any of these options but that’s probably all that’s available to you that I can think of. Sometimes the tubs are a little bit shorter and this can happen.
Thank you very much for your fast reply. To build upon your suggestions. 1) If we go with the option of shimming out the studs, what kind of angle on the end of the wall/goboard would you recommend? We’ve been looking for different metal trims but so far did not find anything that would work.
2) If we leave everything as is and place the goboard behind the tub flange, and then use kerdi band to transition from gobard to the tub flange, do you think that may be an option?
3) Repositioning the drain unfortunately is not an option, it would require cutting the ceiling downstairs, moving the drain below sub floor and then reinstalling the tub. Removing all the drywall on one wall and shimming it out is probably a better option, although we would have to replace a ceiling as well, since I have no clue how replace walls with popcorn ceiling and make a smooth connection between walls and popcorn texture.
1. This post covers your edge trim options. If you’re shimming out the wall then I would shim it out as much as you can so you make the cuts on the end of the wall as big as you can. You may as well embrace it, is the way I see it.
They do have a lot more profile options then they used to and you may not see all of them in stock at the stores. This will show some of them here.
2. I don’t think that will work because your tile has to sit flat on the tub. I’ve tried to finess this before and all that happens is you make things more difficult.
Thank you, really appreciate your replies and suggestions. 1) Upon further evaluating different trim options I’ve realized that since out of 3 goboards only 1 is going to sticking out it will be very challenging to cover that with trim. I would need one thick trim on that problematic wall and then matching thinner trims on the other two walls, so things will look asymmetric and be noticeable, sigh.. (i got excited about finding a solution with pencil trim but now realize that it is going to stick out more on good walls and stick out less on problematic wall, unless i am missing something…?)
2) it looks like going with replacement of the whole wall (i.e shimming out the entire wall) and replacing the ceiling is our only option. In this case would you recommend we go with regular drywall/sheetrock or the moisture resistant one for ceiling and wall above/next to goboard. I am thinking about 1/2 in. x 4 ft. x 8 ft. UltraLight Panels Mold Tough (by USG Sheetrock) or will regular sheetrock be just fine and mold resistant is an overkill?
Thank you very much again for your time and advice.
I was thinking that you would tile the front of the small return wall. Then you would only need a normal piece of metal trim that would cover the tile only. An alternative is to put a metal drywall corner on and paint the front of the angle.
This photo that I found on Google images illustrates what I’m referring to: https://images.app.goo.gl/8dvm8CSeyZaYnmbs7
For option 2, I don’t see any reason that you need to remove the ceiling drywall and I would advise against it if you have an attic above. All that you would do is make a big mess of the insulation falling down.
Instead, look into removing the popcorn off of the ceiling. It can be done with a spray bottle and a scraper. FIRST- you’ll need to take it to a lab and get it checked for asbestos. This doesn’t cost a lot of money and is important to know. Here is some information on asbestos and can answer whatever questions that you have about it.
I typically use normal drywall outside of a shower but I think either is fine.
Gerard Robinson says
DECEMBER 13, 2020 AT 11:04 AM
2) If we leave everything as is and place the goboard behind the tub flange, and then use kerdi band to transition from gobard to the tub flange, do you think that may be an option?
Hi DIY Tile Guy
In respect of wall/tile flange joints, my company offer a solution that might be of interest. The solution is explained in the video on the top of the homepage of the website below.
Thank you for your sharing your expertise, it is very educational!
I would appreciate some help with a small but critical project.
A section of my bathroom wall was opened to replace Tub/Shower valve. A total of 6 X 6″ tiles and drywall was removed around the vale and another tile in the centre just above the spout was removed. There are no seams of drywall as the wall was cut along the grout lines. There are steel studs of 1.5″ width.
I am installing Hardiebacker 500 cement board. the board is quite heavy and so are my porcelain tiles.
The question I have is There are two more rows of tile below the spout line to get to the tub lip – should I remove those as well so I get to install the cement board all the way from the valve level down to the tub lip although they are solidly situated but against the original drywall or should I just install cement board in the T-shape in which is was opened to fix the plumbing?
The question is important to me when I consider the weight of the new install and the fact that it is only being held by about 6 screws. Hardiebacker tells me that the studs must be 18 guage. I am not able to confirm the guage. Also if I do this, there will be half tile left near the corner (right of the valve) and 2 tiles left near the outside (left of the valve) they are on studs.
Will opening the remaining two rows (6 more tiles) so cement board meets the lip of tub be the right approach?
Also as there is no seam is it OK to put the mesh tape against the side of the original drywall and the other part over the cement board or should I just use polyurethene caulking and leave it at that?
It would be great if I could add a pic.
Thank you in advance.
If you have extra tile then I would recommend removing the Hardibacker at the studs and replacing it with new. Additionally, the repair should be done with the tile removed past the backer board so that you can screw in through the backer and then cover it with tile. This also helps so that you can mesh tape that seam.
So, if you can make the hole bigger and go stud-to-stud then that’s the best way. If you can’t then I recommend removing one more row of tile around to expose the Hardibacker. Then clean the residue off of the Hardibacker really well. Then patch the new Hardibacker in, mesh tape the seams, and replace with new tile.
I sm so grateful for your reply, thank you!!
I have a follow up question – I bought oscillating tool blade scrape the thinset offand release the tile after removing the grout around the tile. Problem is the blade is only 2.5″ long and the tile is 6″×6″. 2.5″ of the drywall stayed on the cardboard that is still on the drywall between the studs, 3.5″ came off with the tile.
1. Can i rebuild that drywall by laying thinset between the remining drywall since the yellow paper board is intact between the three surrounding tiles?
2. Is there anyway to remove the tiles even it means breaking them and preserving the drywall? These are mono serra tumbled marble tiles. I tried with a carbide oscillating blad but sparks fly off and it makes a small indebt after a long time. I qas trying to cut the tile in half so I could get behind the remaining portion.
If there is a way to break the tiles it might help.
But I need to preserve the remining row of tiles.
I apologize for all the typos – I had posted earlier using my cell.
I bought a diamond grinder blade and I am planning to cut the next row of tiles in half so I can get behind the remaining 3″ half with an oscillating blade and scrape the thinset off after cutting out the surrounding grout using the carbide oscillating blade. This way I should get the 2 to 3″ to tape over the drywall and 2″ tape over the new cement board. I just hope I am able to control the grinder when cutting these tiles.
I’m not aware of any way of guaranteeing that the drywall won’t crumble behind the tile. Oddly, one of the best tools for preserving the drywall was a small demolition hammer. Apparently, it vibrates so much that the tiles come off easier? I don’t know the science behind it but it worked pretty well. But it still didn’t guarantee perfect results.
You probably one need about 1 inch of existing drywall. It tends to crumble in between the studs more than on the studs. Hopefully, your solution will work out well.
I missed the part at the very beginning of the article where you start out with the waterproofing of the backer board (in my case I used Hardibacker) before proceeding on to the various sealing methods of the tub rim to board.
Now I’ve ended up applying fiber tape/kerdi-fix before waterproofing (planning to use Mapei AquaDefense).My question is would the Aquadefense bond to Kerdi-fix/tape area if I apply it now? If not, could I cut-in with the Aquadefense around the Kerdi-Fix/taped seam and not actually cover it and still be waterproofed at the seam via the Kerdi-fix?
I don’t think it will stick to the K-fix but, at this point, just do the best that you can with it. It’ll be good enough.
Hey there – Love your website! We are tiling over our tub on three walls and adding a showerhead. The two side walls are plaster and drywall, around 3/4″ thick. The back wall is an exterior wall, cinder block with the same depth of plaster/drywall I would assume. There is a 12″ space at the end of the tub, we would love to make a little towel cubby shelf area.
Two questions: My plan was to tear out the drywall/plaster to the studs on the sides, but how should I handle the cinder block side?
Also, if we only have a 12″ space, do we have to build a 2×4 wall on the end of the tub, or could we use something thinner, like 3/4″ plywood or a 2×2 stud wall with backer board? The tile will go from tub to the ceiling, as will the wall.
Thanks for your help, you make diy much less stressful!
In my opinion, the best way to handle a masonry wall is to install a waterproof foam backer board over it. Schluter has a good video of using their Kerdi-board over this type of application and other brands are done in a similar fashion. https://youtu.be/7O6bNoS6NW0
For the end wall, you could use 2-inch foam but framing the wall out of 2×4’s and turning them sideways so they are only 1.5 inches thick might work better for what you are wanting to do.
Right, I was kind of afraid that would be the answer. Don’t the schluter boards cost about a hundred bucks per 4×8 sheet? We were trying to do something a little bit more on a budget, I read your article about the go board, but I’m having trouble finding it in my area of Virginia.
Good idea on the 2x4s sideways, And then I’m assuming I would just put 1/4″ cement board over those and then tile? And on the side with just drywall and studs, I should just tear out the drywall and put 1/2 in cement board in its place?
Thanks again for your response, your website has been crucial in my tile projects!
Yes, the foam board is expensive. GoBoard is probably less expensive than Kerdi-board but obviously that’s not advantageous if it isn’t available to you. The only other way of doing it that I’m aware of is to frame it out and then cover with cement board.
I recommend 1/2 inch cement board on the walls. Hardibacker will let you go with 1/4 inch on walls but I would stay with 1/2 inch.
And, yes, it’s probably best to remove the drywall on the one end and replace it with Cement board. If it’s lath and plaster and 3/4 inch thick then you may need to shim out the backer board before installing it.
I have a two-wall separate shower with backer board installed. The pan is prefab cultured marble. I purchased 24″ x 48″ tile for the job. I test fitted two rows of the tile against the backer using clamps and put a level against it and it wasn’t flush against the tile resulting in an approx. 1/8″ gap at the bottom. I determined the problem is the 1″ flange is at a slight angle sloping towards the pan. I put a 1″ wide piece of wood in front of the flange, set a piece of tile on top, and there were no gaps when level put against the tile, so I know the problem is with the flange. Some possible solutions:
1) Even though it would be a pain, remove the bottom backer board and shim bottom out 1/8″.
2) install the tile at bottom of backer board so it doesn’t protrude over the flange and then install a 1″wide piece of tile to cover the flange, as filling the gap with colored silicone wouldn’t look good.
Which of the 2 better options, or other suggestions?
James Upton says
Unfortunately, I think #1 is the way to fix it. However, you will be shimming the tile up sightly at the bottom to level them out and provide a movement gap. This might be 1/8 inch (+/-). But I don’t know if shimming them up 1/8 inch would provide any relief to your situation, or not.
I tried cutting back edge of tile 1/8″ using my handheld wet saw and clamped a steel bar in front of it so I could cut it evenly, and that solved the problem and now tile completely flush against the backer. However, I cut the corner of the back edge too deep and I want to fill it in so doesn’t chip from the finished side if hit against it after installed. What would be the best product to fill in that corner so it’s even with the remainder of the cut…thinset, bondo, jb weld, or other? If jb weld, which item#?
James Upton says
If you’re talking about the back corner of the tile then I would fill it in with thinset. That should fill in around it and provide support.