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.
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.
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 (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!
Hey Roger, I’m not sure if this is the best place to post my question, but hopefully this is an ok spot. I just finished cutting & hammer-chiseling a sloped rough surface into my basement concrete slab where I am starting to build a 5′ x 7′ steam shower. So far, I have the slope cut and I’ve installed/connected a 6′ Kerdi linear drain positioned near the back of the shower, where I will construct a shower seat all the way across the back wall that will extend out above the drain slightly so it’s tucked nicely out of the way. This weekend I’m mudding the floor using homemade deck mud fashioned from topping mix and additional sand since premixed deck mud isn’t readily available.
My question is about waterproofing! I’m a little concerned about it since this is a steam shower. While I like the Kerdi linear drain product, I’m not sold on their membrane using thin set to seal between layers/bands. I used Noble Deck membrane several years back to build a waterproof tiled deck off the back of the house, and I really like how that went together. So I’m thinking of using NobleSeal TS for the shower so I can use their sealant to join membrane sections and inside/outside corners rather than Kerdi’s approach. I did some looking on your site for any tips on waterproofing steam showers, discussion of permeability, etc, but didn’t find anything. My total previous experience is just two Redgard showers, one with my first mud base, both of which seem to be holding up fine as best I can tell. But this will be my first (only hopefully only) steam shower, and I want to make sure I get it right. Any suggestions you can offer about using NobleSeal and/or any other product(s) that you might recommend would be very much appreciated!
Roger, I’m currently redoing my bathroom after a major leak and extreme water damage. I have an exterior wall that is masonry, do I need to put a barrier or insulation between the masonry and corner studs and the 1/2” Kerdi board? If neither are correct what steps do I need to take? Thank you in advance.
Roger, bought your three books, they are helpful. But I need help with a layout. I have 2″ x 24″, 4″ x 24″ and 6″ x 24″ Porcelain tile. Want to use on shower wall that is 96″ H and One wall is 50″ w and the other is 72″ w. Do you have any suggestion for layout as my tile setter is asking me for the layout and I am struggling with the 1/3 rule he is giving me. Thanks, hope to hear back from you soon.
Hi Floor Elf,
Really like and appreciate your site.
I just pulled all of the old tile off the walls and floor for our Jack and Jill bathroom with shower tub combo. We are leaving the old tub and walls in place, so it’s basically just a retailing effort.
I see there is hardie concrete backerboard 500 everywhere. In some areas, there are now holes from me prying off the old tiles; I will replace those. In other areas, the board is in good shape with maybe just a little divot here and there.
I do not see any moisture barrier behind the boards.
After replacing the boards with holes, should I mud or thin set over everything to bring it flat, then install Kerdi on the shower walls since I’m not sure there is any waterproofing behind the boards currently? Also, I’ll read more, but is it thinset to attach KB to the boards, then just thinset tiles to the KB once I’m ready to install them, or am I missing another thinset application in between?
Any issue if I use Mussel Bound for adhering tiles on the non-shower walls?
I have a situation where cement board has been installed and where I thought it was level but after the fact I’ve found some valley’s that may be as much as an 1/8″ some even appproaching 3/16″!!!. I’ve seen youtube videos that addressed this situation by troweling on thinset and leveling the areas with a straight edge before applying the tile. I don’t want to have to redo the cement board if there is another option. The youtube video guy installed plastic behind his cement board. In my case I’ll be using a topical membrane and was wondering if this is acceptable to level the areas, let them dry then apply the topical membrane. Thanks, John
Forgot to mention I’ll be installing 4 3/4″ x 13 3/4″ x 3/8″ tile with unmodified thinset.
It CAN be done that way, but it’s not ideal. Most thinsets should not be built up any more than 1/4″ at the most. Ideally you would float those areas out with wet mud, or pull the backer and install shims over the studs. I would opt for the shims given the choices.
I have had several contradicting suggestions on adding a moisture barrier to my Durock prior to mortor/tile. I have had people tell me absolutely do not do a waterproofing barrier over the durock, just make sure there is a vapor/moisture barrier behind the cement board. I have also had people tell me I should absolutely paint the cement board with a waterproof paint. I’m leaning toward not doing the waterproof barrier over my cement board as it may trap water in the wall that may come from the other side?
If you have water in your wall coming from the other side then waterproofing your cement board is the least of your issues. Look at your waterproofing from the aspect of the studs to the tile. Either one of those methods will work fine, but you need one or the other, not both.
My wife and I have been following your advice to build our shower, we just finished the top slope. However, we plan on using Durrock with Mapei Aquadefense on the walls. Do I still need a vapor barrier before installing the Durrock? And will I need to use modified or unmodified thinset?
Sorry, I guess I jumped the gun on that one. I was just reading through more of the comments and realized Gus already asked about the vapor barrier when using liquid applied membranes. It seems I don’t need it if I’m using the Aquadefense…
Still not sure about the thinset though. I think I need unmodified on the floor (no Aquadefense there) and modified on the walls?
No need for a vapor barrier with mapei AD. Everything EXCEPT schluter requires mofified thinset.
Hi Roger, I installed my hardie backer directly to my wall framing with no vapor barrier. Then I went ahead and installed the tile on one wall. Now I realize the lack of vapor barrier could be a large mistake. The other two walls are not tiled yet so I could still paint red guard on them. Is there anything I can do about the one wall that’s already tiled besides taking all the tile off and starting over?
Yes, you can put redgard on the existing two walls. No, there is nothing else you can do with the tiled wall, it will need to have the tile removed and waterproofed in some manner.
And yes, I realize this reply is likely too late, but the info will be here for others in the future. Sorry for the delay.
Hi Roger. I’m really enjoying obsessively reading your site, and appreciate the time and effort you expend, and have contributed to the beer budget by buying several of your books.
1. In the free waterproof shower construction book, you mention that you consider liquid topical waterproofing (I would use HydroBan) to be better than DensShield. I’m trying to decide between the two. Can you elaborate on why one is better than the other? I’m interested in the DensShield because it’s easier to work with than cement board. But if the official Elvish stance is that liquid topical waterproofing is better, I’ll go with that.
Per a comment in another blog post, it sounds like DensShield is a good choice for the untiled tub enclosure upper walls and ceiling, regardless of whether it’s used in the actual tub enclosure.
2. Would DensShield be an appropriate substrate for the rest of the bathroom ceiling?
3. Would DensShield be an appropriate substrate for the tiled vanity wall and the untiled remaining walls?
I do have a good bathroom fan. This is new construction.
Basically, I want my bathroom to be intact when future archaeologists excavate. Also to prevent the cat bursting into flames.
Hi, we are removing a tile shower from a home that is 30 years old. The stuff behind it is this pumice like gray stuff with chicken wire. What is this stuff and should we pull it out too and start with the studs? Thank you!
That is a mud wall. Yes you should tear it out and begin with the studs. And yes, I know that sucks.
Do you have to waterproof your walls if you use porcelain tile over cement board?
Yes you do. Neither porcelain tile nor cement board are waterproof.
If using Hydro Ban on the walls and floor of a shower, do you put cement board up before you pour the slope?
Purchased your book to do a traditional tile shower. I have two walls that are exterior. My question has to do with the vapor barrier for these walls. Currently they have r21 faced insulation. Can I put the plastic vapor barrier between this and the cement backer board? Or will this cause a situation to grow mold? What’s the correct order here?
Yes, you can put a vapor barrier over that, then just put your backer over that.
I am redoing a spare bath w combo tub shower. I rocked 5′ up all sides and plan on thin setting joints where I have reinforced with mesh tape. The plan is to then Redford the entire thing including celing, then tile. Would this be acceptable? Should I Skim coat the upper green board either before or after redguarding? Thoughts suggestions? Celing has hardibacker. Thanks in advance!
Sounds right. I would skim coat the greenboard, just to flush everything out and fill be pores of the greenboard solidly before redgarding.
Great! ThNks for the quick response. Any tricks to doing the celing tile? My first on those. Probably 12x24s. I plan on doing thinset bullseye pattern on the back of the tiles and pushing to create the suction.
The bulls-eye is the trick.
Last question. Do I need to fiberglass mesh the corners if redgarding the entire thing? I did pretty good with thinsetting all the joints. They already have mesh tape.
Yes you do.
Thanks for all the good info. I purchased some of your books. I am installing a 4×7 shower in a new addition bathroom. I want to go with a nobelseal TS pan liner for the shower base and kerdi for the walls. I already have a drain (the 3 part clap style) and 3 foot liner drain that inserts into the drian inside a gasket. Can I do the traditional shower floor with the kerdi topical walls? How do I transition the floor to the walls. Should I consider using kerdi on the floor in place of nobleseal? If so I know I will have to switch the drain to a topical one instead of the clamping one. Another question… I have 1/2″ pex crossing through the shower secured to top of the subfloor and supplying a hydronic radiant floor to the rest of the addition. I was planning on placing my preslope over the pex. What are your thought with this? Will I have expansion/contraction issues in my mud deck? One last question. With a 4×7 shower I was planning on tiling the 3 walls and having glass close in the other wall as an open shower. So it would extent about 5 of the 7 feet with an opening of 2 feet to enter the shower. Do you think that I will have splashing issues with out a door? Thanks!
Yes, you can use the nobleseal with kerdi walls. Overlap the kerdi over the noble and use the noble sealer between them.
No, you will not have any issues with the hydronic pex.
Maybe, depends on the layout and type of shower head. You can always run the nobleseal over your flooring substrate outside the shower.
Do I need plastic sheeting between my studs and hardie board if I am applying liquid membrane to the hardie on the shower walls? I have seen conflicting opinions on this. Thanks in advance for your help.
In essence, do the liquid membranes provide both a vapor and moisture barrier?
Yes they do, but you don’t need both. Unless you have a steam shower.
No you do not, unless you’re building a steam shower. And there should be absolutely no conflicting opinions on that. They’re likely just confusing the steam shower requirement with a regular shower.
I’m in the process of renovating my bathroom. I went with everything that Schulter had to offer, shower base membrane, ditra heat, kerdi board, 5′ line drain, shower niches, etc. It wasn’t cheap, around $5,000 for material, but their product is far superior to any other waterproofing system. After you’ve installed the floor and wall membranes and kerdi banded everything, you can literally take a shower before installing the tile, it’s that waterproof.
And no, I don’t work for Schulter, I’m just a very satisfied customer.
Not sure if it’s a California thing, but every tile contractor I’ve ever used prefers to float a mortar layer of sorts over green board(but it’s purple now) and a waterproof membrane. Then simply tile to the mortar. They like it because the can get the walls perfectly straight without worrying about the framing. This is true for backsplashes as well. Curious about your thoughts on this.
I’m looking into some options for my house right now. I’m interested in some of these new products and trying to get a good gameplan for my master bath. Gonna do heated floors so I like the idea of the ditra honeycomb there. One guy said he could do the Ditra paper stuff on the walls directly over the purple board for the shower. And another contractor really wanted to float all the walls. Thought?? Thanks for the great info!!
Mud walls as you describe are the best! However, they are a skill which many do not possess and can not be done by diy’ers. I love them, but people simply don’t want to pay for them. Ditra can go over drywall, it’s actually an approved method and the only waterproofing product which can be installed over drywall.
Had a leak in the roof which compromised a portion (3’x3′) of a tile wall in the upstairs bathroom shower stall. The tile that crumbled away from the wall starts at the base of the shower pan and is the width of one side of the shower stall. The tile that didn’t crumble away is very firmly in place. Under the crumbled away tile was a greenish cement wall covering, possibly drywall. It disenegrated from the tile and from the vertical stud. The vertical stud also has horizontal slats stud is in good shape still while some of the slats appears to be weakened. I lysol sprayed the stud and slats to kill any mold. I’m thinking I should replace the weak slats, put a thick plastic barrier up, then the backerboard, then paint with a waterproof membrane to double insure that it’s waterproof. Can I tile over the membrane?
Tile over what membrane? If you use a liquid membrane do not use a barrier behind it. ‘Double waterproofing’ can actually promote mold growth. You want one or the other, never both.
Roger ,so you recommend a moisture barrier over the framing even with hardi board covered by a Kerdi membrane ?
No, I don’t. Where did I recommend that?
I am in the process of dry fitting my floor tile and noticed I had somehow overlooked a small section of wall that is way out of flat (+1/4″) which will also be tiled. Please don’t ask me how, a dog may burst into flame, or just me. When I go back to lay my floor tile, could I use a little of my thin-set to level that low spot on wall like a SLC? Then later, tile as usual. If so, how long should I wait until I tile. It was my plan to do it in a day or two.
Yes, that will work fine. You can tile over it the next day.
I am installing kerdi over wonderboard and tiling it with painted back glass tile in my shower reno.
regarding the unmodified thinset for the kerdi – should I skim coat the wb and let it dry prior to install the kerdi? I read somewhere that could provide a better bonding to the kerdi, as the thinlayer (of unmod thinset coating) would allow the fresh layer for the kerdi to remain softer (drying too fast)
– as skim coat I literally talking about really spreading it thin, almost sponge it in.
Same would go for afterwards:
as the tile mnfr recommends modified thinset, I talked with kerdi, and they said the one selected (laticrete 254 platinum) is a better for the tile, BUT I should also skim coat the kerdi after installed (not sure any longer if had to be mod or unmod). Could you educate/correct me a bit about all this?
Yes, skim coat the wb first, but you don’t need to let it cure before installing the kb. (Why, by the way, are you installing kb over wb???). You also do not need to let the 254 cure before installing the tile, but you can use the 254 over kb. Skim coating both allow a fresh substrate which will not suck moisture from your thinset as well as getting a proper bond by filling the pores of the substrate first.
Thank you for your insights.
Yes, I am an over-doer of some sorts nothing wrong with plain drywall, but it’s a sturdier installation IMO. Looking back now, I should had gone with kerdi boards – it’s amazing how stiff and sturdy it becomes with thinset and/or kerdi-fix
regarding the skim coat for before and after the kerdi membrane – do both have to be unmodified? I would assume the first one so, because it’s what is needed to bond the kerdi anyway; but later on the membrane – before the laticrete, should I go with unmod or use the laticrete already?
last but not least, I bought by mistake a bag on unmodified Custom Building thinset – can I use it to skim coat the WB and then to fill in the ditra squares (yes, I am using it for the floor) before going with a layer of TEC unmod to lay the floor tiles? ( it’s a bit too sandy as you probably now)
Thanks once again
btw, I called it wonderboard, but actually I used hardie backer boards just for the shower area
You can fill the ditra with the custom stuff. You do not need to use unmodified for your skim coats. The unmodified ‘suggestion’ has nothing at all to do with whether or not it will bond. Modified thinset bonds to kb just fine (better, actually).
Thank you for your great site and advice.
I just finished installing 12×24 porcelain tile over hardibacker painted with two coats of redguard. Unfortunately I did not read enough before I started and I used Omnigrip on the walls of the tub area. From what I have read I believe I should have used a non-modified thinset since it dries without air and air is lacking between the redguard and the porcelain tile.
I did a tub bath and a shower bath this way 3 years ago and both have never had a problem. I had let the tile omnigrip dry out since I got distracted on another project, for 3 weeks before grouting and maybe that was what saved me.
I know I was a fool to not use mortar, but all the tiles are cut and attached now.
Three weeks have gone by on my new tub bath. I got tied up again, haha. On this new job the tiles feel tight. I am going to place a space heater in the bath to ratchet up the heat and leave it for another week before grouting.
My fear it that once the bath is used, and as humidity creeps in through the grout, I do not want the Omnigrip to soften, I was planing to grout the 1/16 to 1/18 horizontal gap between the tiles and the tub with non-sanded grout.
I wanted to know if you thought it would it would be a good idea to leave that gap as a weep exit for the humidity since the Omnigrip trapped between the redguard and the porcelain is susceptible to softening.
It honestly makes no difference whether you do that or not. The outside perimeter of the mastic is likely cured, the inside, beneath most of the tile, is not. The reason they seem bonded correctly is because of this, if you pull a tile off you’ll have a big glob of uncured mastic in the center of the tile surrounded by a cured bead of mastic around the perimeter. It’s simply an improper installation and nothing you do from this point, short of replacing it, is going to make it correct or limit the chance of failure. And redgard is used with modified thinset, not unmodified. Schluter is the ONLY company that wants unmodified.
I am having problems shimming the studs above my shower base. So my question is how do you shim studs that have a bow in them or that are slightly twisted? Any help would be greatly appreciated.
Set a straight edge along the stud and place shims behind it until you have enough shims in the correct areas to make it flat.
Shave down the studs with a planer until they are flat and plumb.
Sister new studs next to the bowed ones so they stick out flush with the outermost part of the bowed studs.
Is it acceptable to attach hardi backer to studs without a vapot barrier if you red guard the hardibacker after taping and mudding the seams? Thank you, your site is amazing!