Preparing a Shower Wall for Tile

by Roger

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!

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Lee Mark

I am wanting to remove some old vinyl over a t&g upstairs bathroom floor. Can I lay the kerdi directly on the t&g, and then put down the tiles? Very small area to tile 15 square feet at most.

Or should I put down plywood first?

At any rate, should I apply thin set before the kerdi? What is the icon for total rookie. :eek:

Reply

Roger

Hi Lee,

Yes, you need to put plywood over the t&g, then use thinset to install kerdi over it.

Reply

Darrell

Love your site and humour.

Question…just recently installed a new shower (Kerdi system). Unfortunately I broke the glass shower door getting out the other day. The handle and glass fell to the floor and broke a couple of the 2 x 2 tiles. Not good. How would I go about repairing this floor. Cut out the tiles and replace the schluter then tile again? What about the dent in the styrofoam floor under the tile?

Reply

Roger

Hi Darrell,

Yes, you can remove the tiles and retile. Try to ‘sheer’ the tile off of the membrane rather than pulling. You can fill the dent with thinset, let it cure, then cover it with kerdi.

Reply

MARK

Roger,

Gutted an old surround shower tub combo. put in new tub, and hardie backer bd about 5ft all around the tub walls. This transitions to about a 1 1/2 remaining drywall above the backer bd to the ceiling. Q: can tile continued all the way to ceiling in this scenario or should it stop just above the transition area

Reply

Roger

Hi Mark,

You can go all the way to the ceiling.

Reply

Kelly Henson

We’re building a new home. Saw some purple board like stuff on walk in shower walls. Not sure if there is a vapor barrier behind walls ( one wall is exterior the other is part of the master closet). The surround wall on the soaker tub is just drywall.
Q: is the purple stuff ok to use? Builder said dura rock will be used in shower but…
Q: shouldn’t there be something other than drywall in the tub alcove?

Thanks so much for your help.
Kelly Henson

Reply

Roger

Hi Kelly,

Yes, it should be backerboard. The purple stuff is drywall, it just has a purple coating on it which they claim is ‘water resistant’, but does not stand the test of time, proven by every one I’ve torn out. :D

Reply

Rick

Hi Roger,

I sent you an email with some pictures of my shower. Below is the same question that I asked in the email.

I read in one of your posts to a DIY’er that you recommended to place a vertical slit in the plastic wrap (waterproof membrane) that is next to go on. He was asking you about the shower wall being next to an outside wall. My back wall with the large niche is an outside wall. As you can see in the picture, I have insulated it with R-21 batt insulation. The outside wall has ½” OSB decking, Tyvek house wrap, then 5/8” T-111. I believe that you said in your post to the person that to prevent moisture from being trapped between the plastic and the outside wall, you told him to cut a vertical slit in the middle of the plastic between each of the studs. Is this needed for my situation or did I miss read what you stated?

Thanks for your time and answers!

Rick

Reply

Rick

About the above post. I am using 6 mil plastic as a waterproofing membrane and then 1/2″ Hardi-Backer on my shower walls.

Rick

Reply

Roger

Hi Rick,

You misread it. The only time I recommend that is when a topical membrane such as redgard is being used over the wall. You need to do that to prevent moisture from being trapped in the substrate between two barriers. With the situation you’re speaking of there is a wall cavity between the two barriers, it won’t trap anything.

Reply

chris

Chris

I just have a quick question is drywall and water proof membrane enough water proofing or should I use cement and water proof membrane?

Reply

Roger

Hi Chris,

It is if you’re using kerdi. If not you need to use backerboard.

Reply

Steven Petersen

Hello Roger,
I appreciate all the wonderful advice and experience you are sharing with the world! My situation is a small 6′ X 6′ room that has the toilet, the tube and shower in it. I am planning on installing 16″ X 16″ ceramic tiles on all the walls and !2″ X 24″ porcelain tiles on the ceiling. The room has no ventilation except for a vented fan to the roof that only turns on at specific times of the day. It gets very steamy in there when I take hot showers and the current painted ceiling drips water over the entire floor. I have investigated and found that steam room ceilings require a 2″ drop for every horizontal foot for run off water droplets. I plan on sloping 4″ on the left side with a 2′ run up to the high point and then the same slope down 4′ to the right side of 8″. Should cement board and vapor barrier be used on all surfaced before tiling or should I water proof just the three walls on the tub and shower enclosure? What is best or what would you do for longevity? Thank YOU very much! Steve. :)

Reply

Roger

Hi Steven,

If you get that much water on your ceiling you need two things:

1. A better fan, that thing is useless. :D

2. ALL surfaces in the bathroom need to have a vapor barrier behind them.

Reply

Steven Petersen

I appreciate your advice Roger.
I take the current walls down to the studs and use KERDI-BOARD screwed in with washers, tape with the Kerdi band mortared over the joints and washers to seal them right? This is better or easier than putting vapor barrier behind backer board and tiling over that correct?
Where can I purchase the materials at a good price please?
Thank you very much!
Steve

Reply

Roger

Hi Steven,

It is both better and easier. As far as the pricing – Schluter has what is called MAP pricing, that means you’ll pay about the same no matter where you buy it. Just google schluter kerdi-board in your town and you’ll find the nearest suppliers. You won’t save any money getting it somewhere else unfortunately.

Reply

dave

Hi Roger,

I love keeping up with all of the comments – it’s like a choose your own adventure story but educational :)

In any case I have another question – I’ve been thinking about installing a wood wall in my shower over my kerdi system (I can see you shaking your head already) but my research has been yielding very conflicting information and I wanted to get your 2c on this.

1) In general is this just a bad idea? teak is used on boats all the time and I’ve seen images of wood floors and walls in showers which look great but I don’t get a sense of how durable they are and what kind of maintenance is required (I hear oil every 6-12 months).

assuming think this is something that could be done here are the rest of my questions:

2) I’m looking at IPE instead of teak (it’s cheaper and more dense) – any experience/recommendations either way?

3) can I use tongue and groove boards or should I leave a gap between for expansion?

4) what is the best way to mount these over my kerdi? I was thinking of using vertical polyethelene stringers to mount the IPE boards. Gluing and plastic welding don’t seem to be the right option so I was thinking I would screw the polyethelene stringers through the kerdi into the hardibacker and reseal with redgard or similar then screw IPE to the plastic stingers. Or how do I do this without compromising my kerdi system?

5) should I seal or not seal the wood? I have heard both recommendations from IPE/teak wood workers and dealers. Some say it needs to breathe so that it doesn’t warp while others say sealing will eliminate water absorption which causes the swelling and warping.

thanks in advance

Reply

Roger

Hi Dave,

I have no idea how to do it, but I’m sure it can be done. I don’t know how to do it over kerdi. For construction specifics google info about steam rooms with wood slats, I would do it the same way. Don’t know that sealing the wood would do much good, water will wear down any sealer not specifically made for a shower wall and you’d be resealing it every 30 days.

Reply

Elaine Hughston

I have two questions:
1. Starting vapor barrier at top of studs and stapling down towards floor before installing backerboard. Will leave 1/8″ gap between backerboard and preslope mud.
Where do I “stop” the moisture barrier? Do I pull it below the backerboard and redgard over the preslope?

2. Mud deck is gritty. Should I put Artec/Henry’s feathercoat on the deck to even out imperfections and create better surface to roll redgard on to?

Thanks
Elaine

Reply

Roger

Hi Elaine,

1. If you have redgard on your backerboard you should not have a moisture barrier behind it.

2. That would work, as would skim-coating it with thinset.

Reply

Elaine Hughston

Thanks roger, the redgard will just be along the floor seam where the moisture barrier comes to the bottom of the studs. I plan to redgard the floor so not sure where (at the base of the walls) the redgard floor membrane stops and the moisture barrier meets it.

Also this is a zero entry shower. Travertine 18″ tile on slab, then a small mosaic travertine meets the big tile and slopes into the shower area
Any advice on how far I take the redgard in transition area?

Youve really outdone your s’elf with this site…been telling all the Lowes and HD flooring people to read it. You put the elf in do it your self! Tx

Reply

Roger

Oh. :D

The barrier runs all the way to the floor, the deck mud goes over it up the wall however far (2″ – 3″, whatever your perimeter height is) and the redgard is painted up the wall to a height of 3″ above the finished height of your curb. (If I understood you correctly). Did that make sense?

Reply

Marie

Hi Roger-

A bit of background first for you. We recently replaced the insulation in our 30+ year old attic with a professionally applied foam insulation. The contractors also applied the foam insulation to two of the walls in our master bath- already gutted in anticipation of our remodel. The two walls insulated were the back and side walls of our future new shower.

This week, the plumbing contractors arrived, and put up our new shower. They checked framing, set in the niches, covered the walls with concrete backer board,taped and mudded the seams, and applied Red Guard prior to tiling. The floor of the shower is tile over concrete ( many layers, didn’t see all that was done), not a pan.

First problem-

This morning was the first time we could walk on our floor tile, to get over to examine the niches. On close inspection, the tiles ( mosaic glass and rock on back- subway on interior side walls, top and bottom) do not meet in the corners. There is a 1/4 inch gap there, from top to bottom. Is this a case where you would recommend a backer board of some type to bring out the mosaics to meet the subway? I read on another page about this and wonder if that product would work for us? All tile was applied two days ago and the tiler returns day after tomorrow. Can the mosaic be chiseled out this many days out? Or we stuck with just applying lots and lots of grout and sealant, and hoping for the best?

Second problem-

The bullnose we selected is more or less a pencil sized tile quarter round. This has been a bear to work with, as it arrived mostly bowed. First choice would be to use this as it’s an exact match to existing tile, but how do you miter the corners to fit together rather than sit on top of one another?
If that fails, could we use the mosaic tile as a bull nose instead? If so, how do we go about softening the edges for safety?

Third problem-

I’m not sure if this is a problem or not, but wanted to get your opinion after reading the home page to the site earlier today. Did the installers create a recipe for mold soup by using red guard over concrete backer board over the foam insulation? The foam does not fill the entire framed section. It covers the far wall surface entirely, with air space between it and the backer board, but i can’t be certain that the two don’t come into contact at some points.

If this a problem, what can we do to fix this now?

Thank you so much for the valuable information you’ve already shared here, and your willingness to take specific questions from homeowners in distress, like ourselves!

.

Reply

Roger

Hi Marie,

Something should have been placed behind the tile to bring it up to the subway tiles. That is simply sloppy work. It can be removed, but it will likely compromise the waterproofing, which can be fixed. But it NEEDS to be fixed when it’s removed before new stuff being put in.

I miter corners on my wet saw. Not sure what your question means?

Third problem is not a problem, the insulation isn’t a barrier, the facing on things like faced batts insulation is. Yours is just fine.

Reply

Igor

Hi Roger,

I’m remodelling a bathroom which was built in the seventies. I took off the tiles in the shower and found drywall behind them. The drywall is in a decent condition, except for one spot where it got moist and disintegrated completely. Do you think that restoring the drywall and applying a liquid membrane would be enough to waterproof the shower, or should I replace the drywall by a water resistant backerboard?

Reply

Roger

Hi Igor,

No, because drywall is not an acceptable substrate for liquid membranes, it must be backerboard. You can install kerdi over drywall, but that’s the only exception.

Reply

Chris

Hi Roger, thanks for all your help. What will I need to do at the transition of the cement backer board a drywall to keep it stable? Also is the backer board usually the same thickness as the drywall or will I need to shim or do something else to make it flush?
Thanks again.

Reply

Roger

Hi Chris,

Backer, drywall transition. Some types of backer are exactly 1/2″, some are not. The ones that are not normally become flush with one drywall shim behind the edge of the backer next to the drywall.

Reply

Dave

Hi Roger,

One other question – can you mix Kerdi and liquid membranes? For instance installing my Kerdi linear pan and drain but transitioning to liquid for the walls to save money. If so, how much of an overlap of the liquid membrane on top of the Kerdi is necessary?

Thanks in advance
-dave

Reply

Roger

Yes you can. A 2″ overlap is fine.

Reply

Dave

Roger,

Great site! I gutted my bathroom in my old pier and beam house and have 2 questions about substrate, ditra and thinset.

1) The floor originally had 24″ c-c joists which i reinforced to create a 24″ grid (vs the original parallel joists only) I then laid down 3/4″ pressure treated plywood. Schluter recommends that I further apply an additional 3/8″ OSB or ext grade plywood to use with ditra (not ditra XL). This added height will create a 1/4″ step into the bathroom. Do I need this additional 3/8″ layer is truly needed considering the grid of floor joists and the ditra?

2) is it safe to use laytex based materials such as modified thinset, crack isolators or liquid water barriers on pressure treated wood. Mapei doesn’t warranty this – they say the chemicals in the wood will deteriorate the bond. However, the pressure treated wood nowadays use less coatic chemicals than the old creasote and are not oily, the wood manufacturers say you can paint this material with laytex based paint (yes, different but similar), and lastly my pressure treated subfloor has been exposed for 12 months (I have a bit of a procrastination problem) and is dryer than leftover thanksgiving turkey. Will this be ok?

Thanks
-Dave

Reply

Roger

Hi Dave,

1. If you want your warranty then yes, you need it. Realistically it’ll likely be fine without it.

2. I would not go over PT plywood with anything other than thinset for use under backerboard. If the thinset manufacturer says not to do it I would not do it. Believe me, they know what they’re products are capable of and if they thought it was fine they’d be more than happy to sell you some. I wouldn’t trust it. Why PT plywood???

Reply

Rob

I have put up hardi-backer 500 for the shower walls, but have 1/2″ moisture resistant drywall for the ceiling. The shower is a 38″ quarter round. Originally I was planning on just tiling up the walls and painting the entire ceiling, but now I am wanting to tile a small area (around 4-5 square feet) just above the shower on the ceiling and paint the remainder of the ceiling. The bathroom is well ventilated.

1. Is it acceptable to tile on the drywall in this application? (I know you do not recommend tiling on drywall at all…
2. Unfortunately, there is a seam that runs through part of the area I want to to tile. Should I plaster this seam (and seal it with primer?) or avoid plaster in the tile area all together?

Thank you.

Reply

Roger

Hi Rob,

1. Yes.
2. Tape and mud it with thinset, it can be sanded and finished just like plaster.

Reply

jerry

My shower and tub were all done using drywall back in the 50’s, I had to redo the plumbing behind the walls and the drywall around the tub was still in perfect condition.

Reply

Roger

Hi Jerry,

That’s because back in the 50’s they used a solvent-based mastic. The drywall face would leach the oils and solvents out of the mastic and make them extremely water resistant, if not waterproof. We don’t have that stuff any more. :D

Reply

Jan Chevoya

I am using Kerdi board directly over wall studs for a tub surround. How do I get the Kerdi board flat and level considering the thickness of the flange on the pre-formed tub? Do I use shims on each stud?

Reply

Roger

Hi Jan,

Use shims on each stud or cut a channel out of the back of the kerdi-board on the bottom to fit over the flange.

Reply

Ellen

I gutted bathroom and put in new tub. I put 1/2 Hardibacker wet area cement board. I caulked joints with silicone and installed porcelain tile without out using kerri or a water vapor shield. Will I be in trouble? What can I do at this point to help my situation?

Reply

Roger

Hi Ellen,

There is nothing you can do at this point. It may last a good long while, it may not. Honestly at this point it’s a coin toss. You have no waterproofing behind your tile.

Reply

Tim

Roger,

Quick question…Instead of putting the vapor barrier behind the hardi backer. Can i install the hardi backer with seams taped and mudded, and then apply redgard or hydrobon (spelling???).

Great site!

Reply

Roger

Hi Tim,

Yes, that is the proper way to do it!

Reply

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