If you need to decide which method is best for you I have a free shower waterproofing manual that you can download here. Shower waterproofing manual. Go get it – it’s free! And I’m not gonna use one of those damn annoying pop-ups! I hate those things…

There are several ways to prepare the wall of a shower for tile. Depending upon what was originally there, what stage the shower rebuild is currently in, and what type of tile you plan to install plays a minor part in choosing which method to use.

The most critical aspects of which product to choose are: how much work you’re willing to put in and how much money you’re willing to spend. The end result should be the same – a waterproof box. The methods used to accomplish that vary in effectiveness and cost. So we’ll start with what I consider the most bullet-proof method.

Kerdi Shower System

A company called Schluter makes a shower system called Kerdi. The entire system, which can include everything from the wall membrane down to the entire shower base, is considered by many professionals to currently be the top of the line in shower substrates and waterproofing membranes. And no, I don’t work for them. I don’t owe them money. And they don’t take me on those all expense paid vacations to Bermuda – bastards. I like their products anyway.

The waterproof membrane made by Schluter is called . . . well, Kerdi. It’s bright orange and you can see it from space. It is installed over regular drywall or cement backerboard with regular thinset. It makes your shower a big bright orange waterproof box that glows in the dark. Okay, it doesn’t glow in the dark.

The material is difficult to describe with words, it’s kind of like a fleece-lined rubber(ish) membrane. I like it for two reasons: It is the best available and it happens to be the easiest, least work intensive option (once you are used to working with it). While there is a fairly large learning curve to effectively work with it, Kerdi is fairly easy and very well documented. There is a wealth of infomation on the internet about it. Just Google Kerdi. Go ahead, I dare ya. Noble company also makes a similar membrane called NobleSeal, but it isn’t pretty bright orange.

Liquid Membranes

After Kerdi, a brush or roller applied liquid membrane such as RedGard works very well. It is applied with a brush or roller like a thick paint. It’s bright pink. You coat it once, after it changes to red, coat it again. Usually two coats is sufficient for any shower (except steam showers). After is sets overnight just go in and stick the tile to the membrane itself. It is a bit expensive, but they are also simple and quick to install.

There are several of these membranes on the market, the most common being Redgard. My favorite is Laticrete Hydroban. Laticrete also makes Hydrobarrier and Mapei has Aquadefense. They are all pretty much comparable.

Preparing shower walls with RedGard

If you are building a shower and want a manual describing the entire process you can find it here: Liquid waterproofing membranes for shower floors and walls

Cement or Fiber Based Backerboard

If you don’t want to spend the money for Kerdi or RedGard, this is your next best option. These are products such as Durock, Hardiebacker, and Fiberboard. While the product itself is not waterproof, it is water-resistant. The backerboard will actually hold water, as in water will soak through it. There needs to be a vapor barrier put up between the wall studs and the backerboard.

The unique thing about these products is that, although they are not waterproof, they will not become unstable with moisture. (That just means water doesn’t make it swell up.) To use these you must first install some type of moisture barrier over the wall framing. Get a 4 mil or thicker plastic (mil is just the thickness of the plastic) which can be purchased at places like Home Depot, and staple it to the studs of the wall framing. You can also adhere it to the studs using silicone. Completely cover all areas from the tub to the ceiling. The backerboard is then screwed onto the studs to make your shower walls. Then you just stick the tiles to the wall and shower away.

How to install backerboards

I also have a couple of manuals describing the entire process from the wall studs all the way up to a completely waterproofed shower substrate ready for tile. You can find them here:

Waterproof shower floor and walls manual

If you have a tub or pre-formed shower base and need to only do the walls you need this manual:

Waterproof tub and shower walls

Denshield

Denshield (and others like it) are similar to drywall in that they are lightweight and easy to install.  It is a waterproof core laminated on each side with a fiberglass based face. It is installed like drywall except you need to run a bead of silicone between the sheets to waterproof the seams. You then need to use fiberglass mesh tape over the seams. It does not require a moisture or vapor barrier behind the sheets. When properly installed Denshield is an adequate tile substrate for shower walls and relatively affordable compared to alternative methods.

If you are building a shower and want to use a topically-faced wall substrate you can find that manual here: Building a shower with a traditional floor and topically-faced wall substrates

If you are just tiling around a tub or pre-formed shower pan you can find that manual here: Topically-faced wall substrates for tubs and shower walls

Plain Drywall *DO NOT DO THIS!!!

Yes, you can do it if you must. I absolutely do not recommend this! But I’m also realistic enough to know that if you decide this is what you’re going to do, I’m not gonna be able to stop you from here. You can not just go up to your drywall and start sticking tile to it – ever. There needs to be a moisture barrier between the drywall and the framing. At least then when water gets behind your tile and grout and disintegrates the drywall it won’t disintegrate your wall framing as well. Remember, if water gets to one of the studs not only will you be replacing the shower, you will need to do some serious repair work to your wall framing and possible structural work. Please also note that using this method runs the risk of parts of your wall literally falling apart if it gets wet – drywall disintegrates in water.

And it will. So don’t do this!

Unsuitable substrates for shower walls – no matter what you’ve been told

  • GreenBoard, also known as green drywall. Never use this or you’ll get a lot of practice replacing showers.
  • Backerboard without a moisture barrier.
  • Drywall without a moisture barrier. (I do not recommend drywall as your substrate at all.)
  • Any type of plain wood or plywood. Ever. No, painting it makes no difference.

I’m certain there are a lot of things I’m not thinking of that someone else will. If you wouldn’t let it set in a swimming pool for a week, don’t use it for your shower walls. That should clear it up.

The golden rule

Although there are many products that can be used for your shower wall, many should not be. Regardless of which method you choose one thing to keep in mind is that you need to have some type of waterproof membrane between your tile and your wall framing. Kerdi membranes and RedGard are both waterproof membranes that go directly on the wall. Plastic stapled to the frame before installing your substrate is also acceptable.

The main thing you need to ensure is that no water reach your wall studs – ever. Wood swells with moisture and the only place that excess swelling is going to go is right into the back of your tile. Remember, your tile is not waterproof so you want to adhere your tile to a substrate that is as waterproof as you can make it.

If you need to decide which method is best for you I have a free shower waterproofing manual that you can download here. Shower waterproofing manual. Go get it – it’s free!

{ 1002 comments… add one }

Leave a Comment

  • Ben

    The floor elf ROCKS! I never realized how cool and interesting tile is. I’m gonna tile my whole house!! So be ready, Roger. You’re in for it now….lot’s of questions coming your way

    • Roger

      I ain’t goin’ nowhere. (my wife won’t let me.)

  • Ben

    Hi Roger,
    Thanks for answering all of my questions. Here’s anther one.
    I need to waterproof a shower nook, and a window that is in the shower. I read your article about nooks using kerdi. I can only find the kerdi material in strips, so I was thinking about using redgard or hydroban. I have 1/4 in hardi in the nooks and around the window. I’ve never seen this stuff before. Is it suitable for these applications, and if so, what are your ‘waterproofing tips’ for this technique. Thanks again

    • Roger

      Hey Ben,

      Absolutely it is! Just make sure you get enough coats on there to make it thick enough – about as thick as a credit card.

  • Tim F

    Great Info!
    We are doing a bathroom reno. A 4′ x 4′ (approx) steam shower. 2 walls (1 an outside wall) & 2 walls of glass.
    What should I put on the walls? Green board is no-no it appears. Our contractor has it up not & I’ve started questioning it.
    So if I go Kerdi, do I put regular wall board or cement board? and what on the ceiling? We are planning on tiling the ceiling. What should the ceiling material screw into? studs on 16″ centers? I saw something about 12″ centers.
    Does it matter what size tiles to put on the ceiling? Is 13×13 ok?

    Thanks for the great site!

    • Roger

      Hey Tim,

      The size of tile doesn’t matter – you can use whatever you want on the walls and ceiling.

      The greenboard absolutely needs to go. If you want to use the kerdi you need cement board on the walls. You can use the same on the ceiling on 12″ centers and there needs to be a slope on the ceiling at 2″ / foot. This keeps cold water from dripping on you as you’re using the shower. :)

      A steam shower is a completely different animal and has different building methods than any other normal shower. It is very apparent to me that your contractor does not have experience with, nor knowledge of, proper substrate preparation for steam showers. I would seriously either find someone who does or ensure that he does some proper research before attempting it. Any one wrong thing can have very serious consequences, steam showers are extremely unforgiving.

  • john

    Roger,

    thanks again for the response, dumb question on my part i’m guessing, but the floor is painted strip it yes ? :eek:

    • Roger

      Hey John,

      Yup, unfortunately the paint needs to come up.

  • john

    Roger,

    Sorry, I have to bug you 1 more time, I also plan on tiling the floor of the bathroom, it is a basement concrete floor. My plan is to create a mortar bed to float everything level first, then to tile with thinset . Is this an acceptable application ? Maybe ues a bushing hammer on the floor first to create a better bond between the concrete and the mortar bed ?

    • Roger

      Hey John,

      It”s absolutely an acceptable application – for over 100 years now. :D No need for the hammer, just use thinset to bond your mudbed to the concrete.

  • john

    Roger,

    Hi, thanks for your response. How thick should the firring strips be ? I have been thinking of doing that anyway to save time and the stink of the stripper, not to mention the possibilty of lead in the ancient paint. I don’t want to lose too much space. If i went with 1/2″ treated lumber, then the backerboard, would that be suffice ? From your earlier reply, am I to understand that I do not need a membrane attached to the framing before backerboard is attached ? Also, do I need to put any type of insulation between them ? I watched a few videos of the kerdi system/membrane, it looks to be a great application. Would the backerboard need this type of covering, oris that more typical of going over sheetrock ? My question now would be, do I need to make a new mortar bed inside the berm ? I had planned on confirming a slope and putting the tile diectly to the concrete floor with thinset.

    • Roger

      The furring strips need to be as thin as you can make them and still get a good grab on the substrates. Normally we use 2×2’s for that.

      Once you have the furring strips a regular shower can be built, as I’ve stated above. That, however, includes either a barrier behind the subsstrate or a topical membrane over the face of it. The floor also needs to be built accordingly, that includes a waterproof membrane as well as the proper slopes, tiling directly to the concrete is not a proper shower building method. So yes, you need to create mortar beds for the tile.

      You can place insulation between the furring strips on the wall should you choose to. Kerdi can go over backerboard, it doesn’t need to be drywall – that’s simply an acceptable substrate.

  • john

    Roger,

    Hi i’m wanting to “upgrade” a basement shower. It is a concrete floor and curb, 2 walls are concrete block. I plan on using mulia glass blocks for the other 2. The house was built in 1954, The block walls, curb and floor have been painted numerous times. Should I strip all the paint and somehow seal these surfaces, would it be ok to iether tile straight over, or attach a backer board first ?
    thank you so much
    john

    • Roger

      Hi John,

      You can either strip the paint off of the walls and apply a topical membrane such as hydroban or redgard, then tile directly to the wall – or you can install furring strip and attach backerboard to them and build it as a normally constructed shower. Attaching backer directly to the wall won’t work long-term, you need framing in place.

  • Chris

    I have recently removed my 20 year old tile shower that had begun to leak. When demoing the shower, it was apparent that there had been condensation in the exterior wall cavity. All others were dry as a bone. The cavity had been insulated with faced insulation, and no other vapor barriers.

    My tile setter will Durock the walls and he says he will run his pan liner up the wall a couple feet or more. Lastly he applies Aqua Defense (3 coats). He is saying it is code to use a vapor membrane (on the exterior wall only) behind the Durock even with the Aqua Defense. Also, I called Mapei, the makers of Aqua Defense and asked them about the VB on the exterior wall, and they said, it won’t hurt to use one. Either way, I am guessing I should use unfaced insulation? What say you about the vapor Barrier and insulation?

    • Roger

      Hey Chris,

      I would use the unfaced insulation. If Aqua Defense says it won’t be a problem – it won’t be a problem. If your contractor does it that way, let him do it that way. It sounds as if he is doing everything else correctly so let him at it. :D I do not use aquadefense so I can’t speak to the nuances of the product. I stick with either redgard or Laticrete products, both of which say to not use a barrier behind the backer – so that’s how I do it.

      You did the right thing by calling the manufacturer, and you received their answer. It should be fine.

      • Chris

        Roger….thanks for the reply buddy.

        Out of curiosity, most of the liquid membranes, Aqua Defense included say you MUST use a vapor barrier behind the backer in the case of a steam shower. If its required in a steam shower, then why does everyone get worried about a moisture sandwich in a standard shower installation? In other words, if it doesn’t hurt to do it in a steam shower, then what’s the problem in a regular shower?

        • Roger

          The requirement for it in steam showers serves an entirely different purpose – it is to keep moisture from condensing and entering the substrate from the back of the substrate – from the wall cavity. This is due to temperature differential in the shower. The high heat in the shower causes water to condense on the other side of a neutral barrier. The same thing that happens with a glass of ice water, moisture condensates on the outside of the glass. The same thing will happen on the opposite side of your wall if there is not a barrier to compensate for it.

          If this moisture builds and soaks into the substrate it will eventually reach the inside surface of the substrate beneath the topical membrane and begin applying negative pressure on the membrane, which will eventually compromise it. If the barrier is there this condensation will simply evaporate, if it is not it will end up as water behind the topical membrane, which will debond it an cause it to fail.

          The condensation or moisture in a regular shower derives from water inside the shower. The condensation or moisture in a steam shower (in regards to behind the substrate) comes from the air in the wall cavity. The barrier in a regular shower keeps moisture away from the studs. The barrier in a steam shower keeps moisture away from the back of the membrane.

  • Scott

    Will thinset adhere to painted drywall? I have a closet that I want to convert to a shower. From the sounds of what I have read here, I am thinking that Kerdi over the top of the existing walls would be the best and easiest solution. Your thoughts? Any need to add additional screws? Would I just run the Kerdi from the new shower pan up the wall and then overlap the wall membrane over it?

    • Roger

      Hey Scott,

      Yes, but you want to rough up the paint to ensure a good bond with the thinset. And yes, just run the kerdi over the top of the existing walls. The seams in kerdi don’t matter, they can be either way. What I mean is that you can lap the floor membrane (kerdi) over the wall membrane (kerdi) as well and it will still be waterproof.

  • Randy

    We have pulled down all the drywall in our bath/toilet room (vanity is in separate room) since tile was on the lower half all around. We have removed the tub/tile shower and are having a Kerdi system tiled walk-in shower installed. Before the tiler comes we need drywall put in. Drywall installer suggests green board for a little extra moisture control in the whole shower/toilet area. Doesn’t sound like a bad idea to me. Any thoughts?

    • Roger

      Hi Randy,

      I have all kinds of thoughts. :D Most of which derive from the fact that I hate greenboard. (Unless you are speaking of e-greenboard, which is a cement backerboard) To answer your question, though, I think it’s a bad idea. I know that it is not needed, nor required. If you have a correctly installed kerdi shower with correct installation of your waterproof barrier there is absolutely no need at all for ‘extra’ moisture control – no moisture will ever get to the drywall.

      You can lay rice paper beneath a sheet of kerdi and seal around the sides. If you submerge that kerdi the rice paper will never, ever get wet. Ever.

      You can do it if it helps you sleep at night, but if you’re doing it for that purpose use cement backerboard instead.

  • janice

    Hi, I just spoke with the tech people at Durock. They said: “If installed properly there is no need for plastic sheet vapor barrier behind durock” in a shower installation. I am reading a lot of different sites on the web and everyone says you nneed a vapr barrier behind Durock. It is weird that the manufacturer syas not to. I am totally baffled now. Can you respond????

    • Roger

      Hi Janice,

      Sure, I can respond: Bullshit! Howzzatt? :D

      I don’t know to whom you spoke (I would LOVE for you to send me a name and number, though) but it seems either they are seriously misinformed or the entire rest of the company is feeding everyone else in the world a load of crap – you pick.

      Straight from Durock: “…Where the wall is exposed to moisture, use a moisture-resistant barrier behind …” Doesn’t get much clearer than that. Combined with ANSI and TNA specs which both call for a barrier I think the person you spoke with loses the argument. :D

      And his statement makes absolutely no sense – to be “installed properly” it would HAVE a barrier behind it in a shower installation – his second variable “no need for a barrier…” is null and void as it creates an illogical loop. (Sorry, I went to college for that and everything! :D ) Use a barrier – really.

      Or you could always get that in writing. Or try to, anyway.

    • janice

      Fascincating!!!! I sent him the quote which is from THEIR literature and here is his response. Please give me your response too:

      “Hi Jan,

      That is just a footnote associated with a UL Fire Rated Assembly. It is still USG’s position that a moisture barrier behind the Durock Panels is not necessary unless required by the local building codes.

      *EDIT: I’ve removed the contact information from public view. Without explicit permission from the company or individual in question I will not (don’t even know if I’m allowed to??? – although that normally doesn’t stop me…) post contact information publicly. I won’t do it with my readers either! ~Roger

      • Roger

        Fascinating indeed.

        I have contacted the individual you sent me the information for – thank you for that! (People think I’m just talking out my ass when I say I want to know where that information is deriving – I’m serious) I have also removed his information from public view and edited your post to do so.

        After a couple of emails it was stated to me that it is USG’s position that when properly installed (fasteners, taping and mudding, NO additional product ‘sealer’ application over the hardi – not sure to which product he is referring, and the correct adhesive or mortar) that the durock will not move.

        Agreed, it shouldn’t considerably expand and contract from the given installation. He mentioned short of the wall being smashed into, it won’t move. Again, agreed. He then mentions that if all these parameters are followed, and the wall does not move, then there is nearly zero chance of the grout lines developing hairline cracks. Once again, agreed.

        This is the point at which it comes apart. The specific phrase used was: “It’s these cracks in the grout that allow water to penetrate through the wall and cause problems” That is a direct quote. This goes back to my very first rule and premise which MUST be understood:

        TILE AND GROUT ARE NOT WATERPROOF! It’s apparent that even larger companies have this misconception as well. They are apparently under the impression that should their product be installed correctly and no hairline cracks develop that water will not get back there and cause problems. That is absolutely incorrect.

        I am going to post and begin this discussion at the JB forums where I can get third (and fourth, fifth, etc.) opinions and answers on this. I never think I’m wrong! :D And, as my wife proves time and again – I’m even wrong about that. I’ll post the link to that particular thread once I begin. For now suffice it to say that I vehemently disagree with their position on this particular subject and restate that the TCNA and ANSI standards call for a vapor barrier behind cementious backers in a wet environment. That is without dispute. You need a vapor barrier.

        • Roger

          Here you go Janice: USG does not require a barrier? The thread linked from that one is a very in-depth thread about ICC and IBC requirements as well, if you’re interested. There are a bunch of us tile nerds out there. :D

  • karen

    I am tiling a tub/shower surround and have installed hardibacker over poly to 5 feet above the tub. Now I have decided to continue the tiles another 15 inches up to and over the ceiling above the tub where there is still the old drywall. Do I need to moisture proof that area with a redgard membrane? Thanks.

    • Roger

      Hi Karen,

      You can if you want to – no real need to, though. As long as you have a membrane above where the shower head will be and it isn’t a steam shower or anything like that the drywall will be fine.

      • karen

        Hi Roger,
        The area in question actually starts a few inches below the shower head and runs to the ceiling (about 15 inches). Presently it is just painted drywall with no membrane, and has been for 20 years, as that is where the old cultured marble tub surround ended. The drywall is in good shape and has not been affected by moisture from the tub/shower after all those years. My question is- because I now wish to tile that area, should I put up some sort of moisture barrier on the old drywall or just apply the tiles to the painted drywall?
        Also, should the corners of the hardibacker be taped and filled with thinset or is silicon used in the corners?
        Thanks again.
        karen

        • Roger

          You can actually just install the tile directly to the drywall. The corners of the backerboard should be filled with silicone.

          • karen

            Thanks for your help Roger.
            Karen

  • Lisa Hillstrom

    My husband and I are in the middle of tiling our shower, and in the removal process of the old tile, it looks like the brilliant person before us put the tile right up on the drywall. We are DIYers, but drywall may be a little much. Do you have any suggestions for removing the old drywall–we definitely need to remove it because it is totally messed up and rotting in a lot of places. Any help would be appreciated!

    Many Thanks
    Lisa Hillstrom

    • Roger

      Hi Lisa,

      To be completely honest – just grab it and yank! :D Drywall, especially moist drywall, will come out in pieces and the screws (or nails) usually stay in the studs – they’ll pull right through the back of the drywall.

      • Lisa

        Thanks, Roger! We are going to give it a go!!

  • Scott

    Hey Roger,
    Long time listener, first time caller. Have you used Durock membrane and adhesive before? I’m installing a tile shower. First time I’ve attempted it and I don’t want to end up on Holmes on Homes, (or on your website!). I would rather spend a little more and know it’s good.

    • Roger

      Hey Scott,

      I haven’t personally used it but the guys I’ve spoken with that have seem to like it. It does work as they say it does, so it’s good stuff. You need to make sure you follow the proper installation procedures here: Durock tile membrane installation

      • Scott

        Thanks. I’ll let everyone know how it went when I’m done.

        • Scott

          Been a while, but I finally got that membrane up last weekend. I used the Durock membrane adhesive for the install and for the most part it went well. Followied the directions for applying to Durock backerboard. You are supposed to over lap any seams by 2″. One tip: anyplace that you have to over lap membrane on membrane, let the adhesive dry before you try to apply it. Durock doesn’t really explain that in the directions. I tried it after the edges kept rolling up. I’m confident I have a waterproof shower now. Now for tile…..

          • Roger

            Thanks for the update Scott!

  • Mike

    Roger,

    This site is fantastic! Thank you so much. I am getting ready to install a shower and I am looking at different types of cement board to put up. I am trying to figure out why someone would use 1/4″ thickness board over 1/2″ or vise versa. Any help on this would be great! Thanks!

    • Roger

      Hey Mike,

      Several reasons to make that decision, and most of them have to do with what the backer is butting up to. If you have 1/2″ drywall – use the 1/2″ In some construction there is less than 1/2″ for that transition, 1/4″ can be used to make things flush. It is also used on floors to minimize height issues.

  • Jack Parr

    Roger… should i tile the walls 1st?? or floor?? & once i start to grout, should i grout inside corners or use caulk?? thx

    • Roger

      I prefer tiling the floor first, but it really doesn’t make a difference, you can do it in whichever order you want. Always use caulk or silicone in all changes of plane.

  • Dave Killmon

    Ready to install a Tile Redi shower tray. PUt tray inplace and some studs do not touch tray. Existing shower framing not square. If I install 1/2″ backer board now, it will be 1/2″ shy of butting up to top of shower tray. Do I add more wall studs and align with tray?

    • Roger

      Hey Dave,

      Either that or get rid of the tray and build a mud floor. If you use the tile redi the walls have to line up flush – but you knew that. :D

  • Jack parr

    Roger…thx for your advice & time my friend.

  • Jack parr

    should I instal backboard to a block wall in my basement?? Or should I instal studs 1st??

    • Roger

      Hey Jack,

      You should install furring strips or studs first. Another option would be to use a liquid membrane such as redgard over the block wall and install tile directly to it.

  • Holly

    Hi Roger,

    I’ve been studying your site like it’s a college master’s class and even taking notes from information that I learn from the comments. My husband and I are remodeling our master bathroom. I’m the brains and he’s the braun. It’s my job to come up with the plan of attack.

    We have installed drywall in the shower which we will cover with Schluter Kerdi. We chose
    drywall so we could do the niche per your instructions. Do you suggest thinset or powdered joint compound with mesh tape along the drywall seams in the shower that will be covered by Kerdi?

    Thank you tremendously,
    Holly
    Kansas City, MO

    • Roger

      Hi Holly,

      Neither one, actually. If you are using kerdi the kerdi itself acts as one large piece of mesh tape – it does the same thing. It is easier, however, to first fill the impressions along the edges (where the tape is normally installed) with thinset floated out to make the wall flush, then install the kerdi.

      • Holly

        AWESOME! Thank you so much, Roger! I love it when things are easier in real life than what I make them out to be in my head! ;)

        • Roger

          Me too, rarely happens though. :D

  • Patty

    If we remove to the walls back to the studs can we put 1/2 inch backer board on the wall only with no dry wall? Thanks again! Patty

    • Roger

      Yup. I do it all the time. You do need either a vapor barrier behind it or a topical membrane over it but yes, it is installed directly to the studs.

  • Patty

    Hi I have a question, I hope you can help. We are in the process of going to tile a small bathroom with shower. It had some dark brown shiny paneling on the walls, when my husband removed it the walls are covered with dark brown adhesive or something one wall in the shower has a med gray adhesive on it. It’s is so thick everywhere we’ve been scrapping and sanding on it . It’s like on there. We are making no progress. Can we cover it with that backer board or do you have any advise. Our house was built in 1959 it’s a ranch. Thanks so much! Patty Roberts

    • Roger

      Hey Patty,

      That’s old-school solvent-based mastic – and you aren’t gonna get it off. :D It would be best to remove the walls back to the studs, but yes – you can install backerboard over it if you need to.

  • Carroll

    we are trying to remodel our master bath. we removed the tile from the walls and shower we found the walls were all concrete!!! like 2 to 3 inches thick, the guy busted all of it out the shower walls and floor.I question what should I redo the walls and floor with and repair the holes in the still concrete walls? He started using waterproof drywall but I’m seeing where you do not recommend this!!! PLEASE HELP!!!

    • Roger

      Hi Carroll,

      What you tore out was a mud shower and floor. You can repair the walls with wet mud (similar to deck mud but it has lime in it). There is no such thing as waterproof drywall – so I don’t know what he may be using there. The ‘water resistant’ drywall, such as purple board, is not an approved substrate for a shower, neither is green board – if that’s what he’s using.

  • Mary B

    Roger,
    Thanks for the quick response. Hopefully we will be able to move along with this bathroom reno now. It still seems wrong to put tile on sheetrock just because it is in a wet area but I have read so many rave reviews on Kerdi. My husband was glad to hear your response and I did have to agree with “I told you so” because he had told me the same thing about the weight of the tile being upon itself going down the wall. Thanks again and we wont be listening to any more free advice from the tile guy at Lowes, I don’t think I can get away with clunking him with a bat though!

  • Mary B

    We have purchased the Schluter system for a 3×4 shower stall. Upon Schluters specs my husband put up regular drywall to attach the Kerdi to. A tile salesman at Lowes said that the weight of the tile will pull the paper off of the sheetrock. Do you know of anyone who has successfully put Kerdi over sheetrock? Why would Schulter recommend something that would not last? My husband sure doesn’t want to replace the sheetrock. They dont recommend cement board so it seems the only other option would be green board which seems like would not be that much different from sheetrock as far as the paper on it goes. Any suggestions?? Thanks!

    • Mary B

      By the way the guy at tile guy at Lowes had never even heard of Schulter.

      • Roger

        Hi Mary,

        The fact that the guy at lowes told you that shows exactly how much he knows about any aspect of building a shower! I can tell he’s never heard of schluter. The paper face WILL NOT pull off the drywall – that’s absolutely ludicrous. The forces applied onto a wall, be it the membrane itself or the substrate beneath it (drywall), is sheer force, not a load force.

        In other words, gravity is pulling the weight of the tiles down the wall – not away from the wall. A tiled ceiling would be an example of load force, where every ounce of the tile is pulling on the substrate – and even that doesn’t pull the paper face off the drywall. Imagine laying the board on a bench, grabbing the paper face at the bottom of the board, and pulling it off down the face of the board. Not peeling – pulling. It isn’t gonna happen.

        Schluter does not recommend something that will not last. I do know someone who has successfully put kerdi over sheetrock – me. I do it literally every week. If it were to fail I would be in a world of shit – and I’m not. And I won’t be, because it works.

        Go back into lowes and smack that guy with a bat. :D Then give him my website address.