Waterproof Shower Manual

by Roger

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Frank

Hi Roger:

Another question if I may.

Is it advisable or necessary to mud and tape the drywall joints behind the kerdi membrane???

Regards,
Frank
- Roger
  
  Hey Frank,
  
  Nope, the kerdi does the same thing the tape does. It’s not needed.
Sid

Hi Roger,
Great website! I’m so glad I found it. I think I went to the end of the internet to find it. The timing couldn’t be any more perfect. I’m in the process of a DYI bathroom remodel. Started scratching my head when I came across all the misleading techniques of the hardibacker board going over the tub flange. Those numbers don’t add up. And then there is the tar paper, hardibacker, and redgard combo. Extra good right? Nope…that’s called a moister sandwich. So tomorrow I’ll be reading your manuals. As they say, “If you don’t have time to do it right. Then you must have time to do it over. Thank you for all your shared knowledge.

Regards,
Sid
Frank

Hi Roger:

I am in the process of remodelling our ensuite bathroom. It will have a porcelain tile floor. There will be a 36 inch corner shower with curved glass doors and 2 tiled walls, also porcelain. The shower has a prefabricated fibreglass base with a 1 inch lip that fastens to the wall studs. I’m am seriously considering using Kerdi wall covering over drywall backing. I’m not sure that I want to tackle the installation myself. I did talk to a contractor but he said he didn’t like working with kerdi because it was too hard to get the air bubbles out. He said he prefers using greenboard with a Redgard membrane. My research has indicated that greenboard is not recommended for this type of application. What is your opinion??? I’m almost tempted to try installing the Kerdi myself. I’m reasonably handy once I know what I’m supposed to do. Again what’s your opinion/advice?

Thanks,
- Roger
  
  Hey Frank,
  
  Greenboard is absolutely not an approved substrate for redgard. It should NOT be used in a shower.
  
  Honestly I see absolutely no reason you shouldn’t do it yourself. Your wall substrate is small enough that the kerdi is not going to be unwieldy. It is NOT difficult to get the air bubbles out of kerdi if you mix the thinset correctly and work from the center out. It isn’t like a massive piece of linoleum, if you can’t get the air out you can peel it back to do so. I’ve never had a problem with that, even with my first shower.
  
  My kerdi walls manual in the library describes the complete process and gives you all the things to look out for. Pick that up and do it yourself, it’ll be a hell of a lot cheaper, too. (Wow, that sounded like a shameless plug, didn’t it?) You can do it without the manual too. There, now I don’t feel sleazy…
- Frank
  
  Hi Roger:
  
  Thanks for the info. You confirmed my belief about the degree of competency of the contractor that was touting the use of greenboard and redgard to waterproof the shower. I think I’ll pass on him.
  
  At this point I’m considering tackling the whole project myself (i.e. tiling the bathroom floor and the 2 shower walls.) I just have a couple of questions to start with if I may pick your brain.
  
  The bathroom is 91 inches by 78 inches. The porcelain floor tiles are 17 1/2 inches square so obviously need to be cut. The question is should I start with full tiles on the long wall and cut just the tiles along the wall on the other side of the room? That wall is mostly covered by the vanity and 1 shower wall or should the start line be down the centre of the room with cut tiles on both side walls?
  
  The tiles for the shower walls are 11 3/4 inches square. The tiled portion of the shower 2 corner walls need to extend out approximately 38 to 40 inches from the corner on each wall. So again cutting is required. The question is should I start with full tiles in the corner and cut the outside ones or start with full tiles at the outside edges and cut the tiles in the corner?
  
  By the way I plan to use ditra under the floor tiles. Is that a good idea?
  
  Thanks,
  Frank
  - Roger
    
    When possible it is said to begin with a full tile, or a grout line, down the center of the room for ‘balance’, whatever that may be. In reality I prefer to have full tiles along the longest wall, the tub, or the largest noticeable space. From your description I would likely begin at the longest wall and cut the tiles on the opposite. And yes, ditra is a good idea, it’s what I use in 95% of my flooring installations.
    
    On the shower walls always begin with a full tile on the outside edges and cut at the inside corners.
Amanda

I’m back and I have an issue…… My dads carpentar had installed the cement board in the bathroom after I reminded him that we would be tiling in there. He’s had some attitude since I overruled his opinion on the shower and went with the kerdi shower kit for the shower which my mother and I will install. So here where my problem comes in…. the cement board extends beneath the drywall so I can’t tell if he left the rigth amount of space for expansion, then there are four corners that come together in the middle of the floor where they should have been staggered, then the floor in the shower is not one piece of cement board but one plus two small pieces that are not level, and finally, while he did glue the cement board down he used what appears to be finishing nails from his nail gun instead of screws, and I just thought it out and I think he used drywall screws in the shower on the cement board that was installed!!! What should I do, remove all the drywall screws and replace them with the correct screws, then screw down the floor ? or should take out the cement board on the floor and do it right by my standards?
- Roger
  
  Hi Amanda,
  
  If you are using kerdi on the shower walls then just leave the screws, water won’t get to them. The cement board can be installed with nails, it’s an approved method (one which I don’t agree with, but I don’t write the specs…). If you are installing either a mud deck or the pre-formed schluter pan then you don’t need to worry about the non-level floor there, mud will compensate for it as will thinset beneath the pre-formed pan.
  
  I’m more concerned with whether or not there is thinset beneath your backerboard on the floor. If there is not then it needs to be removed and installed properly. If so then you’re likely fine, just be sure to leave expansion space around the perimeter in the tile installation.
Chris

Elfie,

I’m thinking that I want to use urethane grout on the shower I am about to install in the tropics. Mud preslope, kerdi drain & “pan”, durock walls coated with redqard. “Mold sandwich” issues with the urethane grout?? Mold here is a HUGE issue. I am tempted to redgard the ply subfloor even, just as added insurance. I’ve been here too long and seen too much rot …
- Roger
  
  Hey Chris,
  
  No mold issues to be concerned with when using urethane grout over a kerdi shower.
Anita

I just had a shower enclosure removed and replaced with a tub. I’m still going to use the shower, but the builder installed a purple drywall around the tub. It’s a drywall that they sell at Lowes that rates high against resisting mold and it is moisture resistant. However, I don’t think I should tile directly on it. Removing it is not an option. What would be the best thing to do before tiling it to make sure it’s waterproofed. Should I install something like kerdi, plastic sheeting, or redgard and then put up backboard before tiling? What would be the best way to do this?
- Roger
  
  Hi Anita,
  
  Your best bet would be kerdi directly over it with thinset and tile installed directly to the kerdi. No need for backer. Alternatively you can install backerboard over the drywall and install redgard over it, tile is installed directly to the cured redgard.
  - Anita
    
    I was on Lowes website and they sell Kerdi. The description says it “waterproof/ protects subfloors, and is a lightweight alternative to backerboard”. Since it says it protects subfloors, is it still ok to use on walls? Or is there a different version for that. I only saw the one on Lowes site. Thanks by the way for responding so quickly!!
    - Roger
      
      The kerdi is for waterproofing purposes in wet areas like showers, ditra is for subfloors to be used in lieu of backerboard. Lowe’s mixed them up or something.
Amanada

Morning, I subscribed this morning, but my little laptop isn’t tough enough to view the manual, so I have to wait untill I get back to my other computer but I had a question and can hardly wait to settle in my mind the answer. I bought the kerid shower kit, but haven’t had time yet to open it up and expamine the complete instructures. What should I use behind it for the best wall base? I read in your main page to avoid green board but I’m not sure if thats ingeneral or even with the kerdi. could you please clarify for me.
- Roger
  
  Hi Amanada,
  
  Green board is no longer approved for use in or around wet areas. It can be used behind kerdi, but it shouldn’t just on general principle. If it’s already up there then leave it, but if it isn’t yet installed then use either cement backerboard (best) or regular drywall.
  - Amanada
    
    What would be your most highly recommended material. My carpentar is going to argue with me on this. I was going to use the cement board but couldn’t figure out the transission on the wall from the board to drywall. So it is better to use regular drywall rather then green board? how come? I thought GReen board was water resistant, wouldn’t it repel water? should I put up some sort of water barrier all around the bathroom? Its completely gutted right now includding most the floor.
    - Roger
      
      Greenboard is no longer approved for wet areas. It is also not recommended behind kerdi. It feeds mold. Cement board butted up to the drywall and taped and mudded, just like drywall, is the best method. No need for a barrier all the way around unless you want it.
      - Amanda
        
        thanks, I had read your reply some time ago but hadn’t had time to reply back thank you. what about using green board at the top of the shower on the ceilingis that a no no?
        
        Roger
        
        Nope, that’s fine.
Brody

Roger –

I am doing a shower redo and have been doing a lot of research so I can get it done right and wanted to get your opinion on a couple of things. I am planning on doing a Kerdi Membrane over a shower base I have installed. The base I am using is a Lyons Elite Seated Shower Base.

Here is a link to a picture of it: http://www.menards.com/main/plumbing/bath/bathing/shower-bases/elite-48-x-34-x-20-rh-seated-shower-base/p-1481607-c-8349.htm

At the top of the base there is a lib that attaches directly to the studs. I have attached my drywall down over the lip about 1/2 from the top of the base.

I saw in the Schluter Kerdi Installation manual on using Kerdi when using a Tub, and I would assume I would follow the same directions. Where I first start with attaching a Kerdi Band at the bottom and using Kerdi Fix to run a bead of sealant between the Kerdi Band and the shower base.

I would then install the Kerdi on the walls.

Does this sound correct so far or do you have any better suggestions?

I have C-Cure 911 Dry Thin Set right now that I was planning on using to install the Kerdi, but after reading your site was thinking about possibly switching to Mapei Kerabond because that is one of your “best” ones that I can get locally.

I have a 1/4 x 3/16 v notched trowel to put the thin set up with. I would assume that would be good?

Other concerns I have is about thin set thickness and consistency. I have tiled many times, however, this is my first shower wall tiling job.

Would you believe that installing Kerdi is something that shouldn’t be too hard for a first time wall job when I have done tiling a number of times before? And do you have any additional tips or tricks that might help the process and make sure it goes more smoothly?

Thanks for all your help!!
- Roger
  
  Hey Brody,
  
  Your order of events is correct. I would switch to the kerabond if it’s available. The trowel is fine. Installing kerdi is simple enough provided you take your time and ensure you get good coverage. The best advice I can give you is NOT to peel the kerdi off after the thinset is cured. People do that for some reason. It’ll peel off a bit, but tile never puts that type of stress on it.
  - Brody
    
    Thanks Roger.
    
    When mixing the thin set any tips on getting it mixed to the best consistency? And what is that consistency?
    
    And when you say take your time, how much time do you think I would have for each wall before the thinset starts to setup? I have three walls, two are about 3’x6′ the back wall is 4’x6′. On the back wall I plan on placing the Kerdi horizontally and then fill the seam with Kerdi Band.
    
    Thanks again.
    - Brody
      
      Forgot to mention a couple more things in my reply.
      
      I used to have one of those all in one showers in that place. So at the top there was already drywall, that was painted like the rest of the room. Will the thin set and Kerdi stick to that painted drywall or should there be additional steps taken on that painted drywall? Also, between the drywall sheets I have not taped or mudded anything, is that ok?
      
      Lastly, I am going to be tiling with 3×5 white subway tiles, with the tiles being so small is there anything else I should be concerned about when putting the Kerdi on the wall so that there won’t be problems when putting the tile on?
      
      Thanks!!
      - Roger
        
        You want to rough up the paint a bit with sandpaper so the thinset will bond well. No need to tape and mud the drywall, kerdi does the same thing essentially. No worries with the 3×5’s, no different in that respect than anything else.
    - Roger
      
      Hey Brody,
      
      Consistency to install the kerdi would be about like pancake batter. Just thick enough to hold the ridge of the trowel. Once on the wall you want to get your kerdi up withing 10-15 minutes. When I say take your time I simply mean don’t try to rush through it, be particular.
      - Brody
        
        Roger –
        
        Ok, The Lowes in my area no longer carries Kerabond. I can’t seem to find Megabond or 317 either.
        
        Any other suggestions for thin set. I’m in Wichita, KS and can’t seem to find any goods ones. The tile store I got the Kerdi from are the ones that recommended the C-Cure 911 that I originally had and was going to use.
        
        When I talked to the guy at Lowes he said the Keraset was the best unmodified they had.
        
        Being that this is my first Kerdi install I really want it to go smoothly and it sounds like the thin set plays a big part of that.
        
        BTW, I was just around your area visiting family. If I would have already been looking here I could have gotten in contact with you to get the proper product.
        
        Thanks again for all your help.
        
        Roger
        
        Hey Brody,
        
        The 911 would be your best bet short of ordering some 317 online somewhere. That requires shipping, which isn’t cheap. The 911 will be fine.
Rob

Hello Roger,

I’m building a new 4’ X 5’ shower in my basement. The pre slope is done. Walls are framed, but I do not have the floor line down or backer board up yet. My wife wants a bench in the shower now. Could you please give me some advice on the best method for building and waterproofing a bench without causing my dog to burst into flames? The bench will be tiled.
Thank you very much,
- Roger
  
  Hey Rob,
  
  The easiest way is to build your bench into the framing and run your liner up over the top, and up above just like you’re doing another floor on the top of the bench. One continuous membrane from the drain to above the bench. Easier than that would be to build your bench into the framing, install your liner and top deck, install your backer then use a topical membrane such as redgard down over the bench overlapping the top of the membrane. With either make sure the top of your bench is sloped correctly beneath whichever waterproofing you choose.
Linda

Don’t know if anyone has asked or answered this question here, but here goes. I ripped out my bathtub (after part of it fell through the floor) and redid the floor with new plywood + cement board… all except for that little plumbing trap that held the bathtub drain. I just couldn’t figure out what to do with that, if I should seal it or leave it open. Anyway, I’ve decided to install one of those “goof-proof” showers where my tub used to lay. So wth do I do about that plumbing trap? Thanks for reading.
- Roger
  
  Hi Linda,
  
  It is normally rerouted to use for the new drain. Pipe is added, removed or channeled to meet up with the new shower drain. Your new shower will have a drain, yes? It needs a plumbing trap as well.
John

Roger,

My wife and I are doing a major bathroom/laundry room remodel. The remodel includes building a shower into our new bathroom. I have two things to ask about.
1) We have an older home which has it’s original lathe and plaster walls. I know this might be a dumb question but our new shower will incoperate two exhisting walls with the third being new construction. Need/Should I take out the original lathe and plaster down to the studs or if I’m mounting the cement board to the studs and using a liquid membrane can I skip the extra labor of demolition?

2) I have purchased a Tile-Redi Shower pane , which is currently being shipped to me, however I wish we had discovered your website before I had ordered the pan as I actually had no idea (because the DIY store clerk didn’t mention it and was probably also not aware) that the tile-redi pans require an epoxy to tile. (btw the store’s cute little how to video forgot to mention that as well) But my question is How big of a pain in the but is this?

It might be important to include that this is our first tiling project.

any advise will be greatly appreciated
- Roger
  
  Hi John,
  
  If you are using redgard for your shower walls you do not need to remove all the lath and plaster. Although it would be better, and plaster is not an approved substrate for redgard – it works. (Don’t tell the tile police I said that… )
  
  Epoxy setting material is a pain. The time issue is the biggest you’ll need to deal with. The epoxy should be included with the pan, you can weigh out the liquids and powder and split them into smaller, manageable batches, that makes it much easier. Don’t wear your church clothes when you do it.
Galina

Hi Roger,

thanks so much for waterproofing manual – easy to digest. I am planning the bathroom remodeling. Plumber will change the bathtub, but I want to change the tile myself
I have an idea how to remove the old tile and install the new one, But – should I waterproof walls before new installation? Please help

Thanks!
- Roger
  
  Hi Galina,
  
  Only if you plan on using the shower. It does need to be waterproofed in some manner, the method is up to you – that’s what is in the waterproofing manual. It’s normally easier to remove the entire wall with the tile attached than it is to attempt to remove individual tiles. I don’t know how big of a wall you can carry, though. I can carry pretty big walls.
  - Galina
    
    Thanks:)) the thing is that I am removing only 2 rows of tiles and planning to install 1 2×2″ row – the new bath is much higher than the old one. House is about 40 y.o., so I thought it has “traditional” waterproofing and if I remove the tile carefully and don;t damage backerboard – I shouldn’t worry about additional waterproofing. I just don’t want to buy a big bucket of RedGuard and use 3 tablespoons (I will, if necessary, just want to understand if it’s really necessary:))….. well, it’s all sounds stupid girl’s talk….. will appreciate any feedback…
    - Roger
      
      Oh.
      
      Your replacing a bathtub, not remodeling an entire bathroom. As long as the walls are in good shape (no water damage, etc.) and you carefully remove the tile you can go right over the existing with new tile. Be sure to place a bead of silicone around the new tub before installing the tile to seal the transition to the wall.
Joe

I’ve been looking at books to get ideas for remodeling my bathroom. One book had a picture of a bathroom with a shower in the corner (not a separate shower but shower head and faucets coming out of the wall, I think it was a “wet room”). The walls and floor were not tiled. The darn book gave no information on what the walls and floor were made of. I like the idea of not having tile but have had no luck in finding any information. Have you heard or seen of such a thing?

Thanks,
Joe
- Joe
  
  Forgot to mention: Whatever the surface is, it is paintable because the book did mention the brand and color of the paint used.
  - Roger
    
    Hi Joe,
    
    I’m sorry, I don’t talk to people who don’t like tile.
    
    I don’t have any idea what that would be – I’ve never seen it. I imagine you could do concrete walls and floors and coat them with either an epoxy or acrylic made for tubs or boats – but I really don’t have any idea what it may have been since it was paintable.
    
    Sorry, I’m a lot of help, huh?
Dianna

We recently purchased a 13 yr old house. After a month or so we noticed a lot of mold in two of the showers. We decided to replace the tile starting with the smaller br first since we don’t have much experience. Upon taking out the tile and backer we found all kinds of interesting things. First, the builder used some sort of backer with a blue barrier but only about 2 feet up the wall. The rest of the shower was green board. There was a vapor shield half assed tacked to the furring strips on the concrete block walls but nothing on the one interior wall. The pan liner was cut at the corners next to the curb. Tile was adhered straight to the vinyl liner. There was no pre-pitch when we took out the mud bed. In fact, there is a shallow trench all the way around the shower floor perimeter. Oh, oh, and you guessed it…MOLD. The pan liner, backer board, vapor shield, tile, it goes on.

Now, I am not an expert as I stated before but come on. Common sense tells you where the water is going.

I know you want to know where I am going with all this. First, I’m venting. Second, being paranoid that this will happen again I want to make sure I do this right. Since we have concrete block walls here in Florida, do I need a vapor shield/barrier and a water proof membrane or just the membrane? Also, can you use the pan liner and put the liquid liner on the Hardi backer? I didn’t know if that would make sense if you have to put a mud bed in after the backer board which would soak up water anyway. Does that make sense?
- Dianna
  
  I need to clarify something. The tiles were adhered to the vinyl on the curb. I assume that is were the compromise began. There was a mud bed on top of the liner but it wasn’t pitched very well.
  - Roger
    
    Hey Diana,
    
    With concrete block walls you can use a topical membrane right over them, but you’ll also need to use a topical membrane on the floor. Unless you can install a floor with the liner, then the backer over that, then you can use a topical over the walls. So yes, you can use a liner with a liquid membrane on the walls, you just need to make sure the liner is run up the wall behind your substrate. The waterproofing on the walls need to run down into the pan.
    - Dianna
      
      Hi again Roger,
      
      I love your website by the way. We are going to pre-pitch and use a liner. I guess we’ll have to decide which we want to go with. No problem.
      
      Now, I mentioned before that there is a trench in the concrete floor of the shower around the perimeter. Do I need to fill that before the pre-pitch or will the pre-pitch take care of that?
      - Roger
        
        Just fill it with deck mud as you’re creating your pre-slope (or slope, if you use a topical floor).
Dave

Hey, I must have had too much to drink last night. Here is a better description. I am putting in a walk in shower, about 40″ x 100″. My drain is 30″ off the back wall and my shower head is on the long wall with the shower access door. I put in a plastic sheet as a vapor barrier, then tar paper over that. I installed an oatey shower liner for the shower pan, and I have cement board as my substrate. Unfortunately, I put the oatey liner right on the flat concrete floor.

1. Can I put my sloped mud deck over the top of my flat oatey liner?

2. I am a rookie and have never done a mud deck. Any tips on pouring a bigger deck?
- Roger
  
  If you don’t yet have a mud deck on your liner then you’ll need to install a preslope first. With larger floors just take your time and only do as much as you can reach over at a time.
Dave

I put it in before I found your web site. It is very helpful. I wished I would have found it before.

I used an oatey liner on a flat concrete floor. Question; Will that be OK or will i need to put a water proof coating on top of my mud deck?
- Roger
  
  Hey Dave,
  
  Your only viable option at this point is to either leave it as is or tear it out and do one with a preslope, or do a single layer with a topical membrane. You do not want to install any type of waterproofing on top of that deck. It may create a mold sandwich. That will cause many more problems than it will solve.
  - Dave
    
    Sorry, I am kind of dense here, I guess I kind of know what I did is not right but I do not want to tear out what I have done. So are you saying I can leave my oatey liner on the flat concrete floor and put my sloped mud deck over that?
    - Roger
      
      You can, but you’re correct, it’s not right. It may lead to problems – it may not. I can’t guarantee a failure but I can give you methods that will not fail. A proper floor with a pre-slope will not fail provided it is installed correctly. A flat liner is likely to have mold and/or mildew issues sooner or later, all the water in the liner will never fully drain.
      
      If it were up to me I would take it out and replace it with a properly built one. But it’s not up to me, eh?
      - Dave
        
        Thank You. I kinda knew that was the case.
        
        If I may with one more question. Can my pre-slope go to the drain I set for the flat floor or will I need to raise it up to som minimum for a pre-slope mud deck?
        
        Roger
        
        You can go right to the existing drain. Just make you pre-slope a hair higher than the bottom flange of the drain.
        
        Dave
        
        Thanks for the tips. I got my pre-slope in after fretting for weeks, it wasn’t that bad.
        
        Dave
lynn

just starting a retile of a shower that has a concrete floor below the tile. Previous tile job was done directly over the tile wiIth no “barrier” or anything below the tile. I am reading your info but would like a “quick” answer to get me motivated to go on ! Do I need to put anything over the concrete floor before starting the tiling process? I’ll bet I do, since the reason we are redoing the floor is that apparently water is leaking “somewhere” and some of the bottom row of wall tiles are obviously wet and we need to remove them and the floor. Probably the grout on the floor failed – maybe too aggressive “cleaning” ?? THANKS
- Roger
  
  Hi Lynn,
  
  Your quick answer is yes, you need a proper barrier in place for a correct shower construction.
  
  Everything is wet and leaking because tile and grout are not waterproof. Your entire substrate needs to be waterproof before tile and grout are installed to it. That has nothing at all to do with the grout failing. The grout likely failed because there is no waterproofing in place, water saturated and swelled your (wall) substrate, cause the tile to move which in turn caused your grout to fail. Failing grout is normally a symptom of the problem, not the cause.
Lori

We’re adding a bathroom to our house and asked the contractor to do everything necessary for the shower stall except for the tiling, which we will do ourselves. They say they’re done, but the cement backerboard seams aren’t taped and mudded. But that doesn’t concern me as much as the fact that I saw how they did the plastic moisture barrier before they put up the backerboard and I don’t know what to do now. The membrane they put in only covers the shower stall floor, and maybe goes about a foot up the wall. I downloaded your manual and read that you should either do a moisture barrier behind, or in front, not both. But since the moisture barrier doesn’t go all the way up the wall, should we do a topical membrane on top of the cement board?
- Roger
  
  Hi Lori,
  
  The membrane on the floor is your pan liner, it needs to go up a minimum of 3″ above the curb – so that sounds fine. It doesn’t sound like they put a barrier behind your backerboard, or did they? You said the ‘plastic moisture barrier’ but the latter part of your question sounds like they only have the pan liner in there.
  
  If there is plastic behind the entire backerboard then no – you don’t need a membrane on the face of it. If the only barrier you have in your shower is the pan liner which runs up about a foot then yes – you need a barrier on the face of your backer before you tile. The pan liner running up the wall a foot is not going to cause the problems I describe with the double-barrier. That describes two full membranes with your wall substrate between them. You can cover the entire face of the backer all the way down to the floor – the pan liner behind that portion of the wall will not cause any problems.
  - Lori
    
    Thanks so much for the response!
jim

Thanks for the quick response Roger. What I meant by the vapor barrier question is that the entire house is wrapped in unfaced insulation and covered with vapor barrier (plastic). the back wall I was refering to in the bathroom is an outside wall. I just wanted to double check with you that if I remove the vapor barrier, the kerdi will perform the same job as that was doing. I live in upstate ny and it gets quite cold up here. Thanks for your book, it was an eye opener and gave me a big piece of mind,
- Roger
  
  That’s what I figured, just needed to make sure.
  
  Yes, the kerdi will do the same thing, it’ll just have a layer of backer in front of it.
jim

Floor Elf;

I have a question, I recently took out a perfectly good one piece shower, why you ask? because the wife did not like the color any more. Mauve), that led to the removal of the whirlpool tub, toilet and sink. Now it is a total rehab because of a color. Anyway elf, here is my question. I have oredered a shower base that is rounded in the front. Will meet the back wall and right wall but will be open around to the back wall again. Also this has unframed glass enclosure with it. Where the shower base hits the back wall (exterior) I have 2×6 studs and renoved the insulation and replaced it. (unfaced) I then put my vapor barrier over the studs. I plan on using hardy board for the back and right side walls.The right side walls sits in the room abot 15 inches. Reading your book, I have changed my mind and want to use hardy board with keerdy membrane. This means that I have to remove the poly vapor barrier on the exterior wall correct? This will leave unfaced Insulation with the backer board over it and then the membrane on the other side. This will still act as a vapor barrier correct? In addition. I am told that the backerboard only goes down to about 1/8″ from the top of the tiling flange so it never contacts it, is that correct? I use tape and thinset on all joints and in the corners even with using keerdi correct? last question, when i leave the backerboard a little off the top of the flange, it will stickout past the flange (1/2″ backer board vs 1/8″ flange). How do i run the kerdi down and underneath the backerboard to I assume adhere it to the flange to make the whole thing water proof.
- Roger
  
  Hi Jim,
  
  The backer can go to within about 1/16″ from the base, but it should not sit on it. The acrylic bases tend to move. The kerdi is a waterproof barrier as well as a vapor barrier, unsure what you mean by that question. You do not need to tape and mud the seams – the kerdi does the same thing once installed as the tape and mud does. It ties the entire wall together. The kerdi runs down over the flange and the back of it is siliconed to the face of the flange. This waterproofs the entire installation.
jen

Hi, floor elf,

I have a question about my shower pan and the caulking around it. Would it be possible for you to give some suggestions?
I got a new shower installed about a month ago. It is cut pebble tile, so it is flat but still more grout than usual. There is hot mop underneath, since we are in CA. The contractor put in clear caulks around the shower pan, where it meets the walls. After we using it for 2 weeks, part of the caulks turned white. So the contractor came to replace those sections. Now after 1 week of usage, those sections turned white again!
What else can we do? My husband suspect that it is because the pebbles are irregular shape and water sneaks behind the clear caulk to turn it white from inside. If that is the case, do we still need caulking around a pebble shower pan? If we do still need caulking, what can we do to prevent it from turning white again?
I’d like to show you a photo of the caulk but haven’t figured out how to post a photo here.

Anyway, thanks for any advice you can share.
Jen
- Roger
  
  Hi Jen,
  
  It could be a number of things. One being what your husband suggests, that it is allowing water build-up and is turning white, which can happen if it is an acrylic-based caulk rather than silicone (which it should be). Another possibility is latex leeching from your setting material (the thinset).
  
  What I’m afraid of, though, is that a pre-mixed mastic was used to install your wall tile and it is re-emulsifying behind your tile and running down the wall behind the caulk. If that’s the case then you have larger problems than a simple bead of caulk. When the tile was installed do you know if they used thinset? It would have been a powder mixed with water to bond the tile to the wall. Or was it a pre-mixed adhesive, normally white, scooped out of a bucket?
  
  You can upload photos here: FloorElf’s upload page
hoke hinson

hello floor ELF,
i learned some good info from you…thanx.
i read some where that when setting the tile onto the redguard treated backerboard the tile should have about 1/8th” clearence from the tub edge.
this sounds correct to allow the water to weep from the edge of the backer board if moristure is absorbed.
could you please advise me on the above subject…
thanx,
tub shower junkie…:)
- Roger
  
  Hey Hoke,
  
  All tile should have a gap 1/16″ – 1/8″ from the change of plane – tubs included. That gap should be caulked and weep holes left in the bead like I describe here: Weep holes in tile installations to assist with drainage.
  - hoke hinson
    
    roger, thanx plenty for your advice & all the work you put into your site to help DIY’ers. so i CAN caulk the lower gap but just leave two weeps holes an inch long as @ the picture in the weep hole article.
    
    thanx…….again!
    
    hoke
Sean

Roger,
We are installing a jacuzzi bathtub in our bathroom.
We would like to use it as a shower as well.
I was going to put cement backerboard up,
paint it with a waterproofing paint, push the tub all the
way up against the walls then fill the gap between with caulk.
We were then going to tile down to the top of the tub.
First time we have done this so I am a little nervous about water leaks.
Sound like an ok plan?
Thanks for any more info.
- Roger
  
  Hey Sean,
  
  You have all the pieces in place – just in the wrong order. You need to put the tub in there first – against the wall studs. Then run your backer down to about 1/16″ from the tub, silicone that gap, then install your redgard or hydroban (waterproofing paint). Then just tile away.
  - Sean
    
    Thank you sir.
    The tub does not have the built in lip so
    I was wrong in my assumption with the backerboard.
    Is there any harm in painting the redgard on the bottom
    of the backerboard and maybe wrapping it around to the back?
    Or would that just hold more moisture in the backer board should
    it ever absorb water?
    Again thanks for the reply and offering your advice.
    - Roger
      
      No harm in it, but no need for it. The silicone bead between the tub and backer prevents any water from getting back there. But yeah, you can if you want.
Misty

Dear Floor Elf,
love your attention to detail!!!

I’ve put up hardibacker and joint taped the seams including 2 shower niches, now I need to know how long to let the mortar dry on the tape before I can paint on the laticrete water tight membrane and then how long to let that dry before I put up the tile??

No floors just walls…’

Thanks,
Misty
- Roger
  
  Hey Misty,
  
  24 hours for the mortar and you can install tile right after the membrane is cured – that varies due to room conditions. You’ll be safe with 12 hours or so after the last coat.
Mike

Roger,

I am considering tiling the floor in an old garage which is being converted to a studio apartment. The floor obviously has a slope towards the old garage door along with control joints in the slab. I have read about testing for water absorbency, flat to within 1/8″ over 10′ (or so…ish). What do I need to know about cleaning, prepping, bonding, membraining (you’re not the only guy making up words around here buddy) and any other associated jargony stuff. Thanks in advance, this site is awesome, I feel like I’m home, ’cause you ARE cool like that.

Mike
- Roger
  
  Hey Mike,
  
  Membraining – I like it. As long as your slab correctly absorbs water so the thinset will adhere correctly and there are no debonding agents on it (stuff like oil stains, etc.) the only other thing you need to take into consideration is bringing the control joints up through the tile installation as well. If you can place a grout joint directly above it, or within three inches or so, and create a soft joint there with silicone rather than grouting it in. That joint is going to move – that’s why it’s there. You need to make sure it doesn’t destroy your tile installation when it does.