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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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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