# Waterproofing tiled shower walls.



## Blondesense

When we bought our current house several years ago, I immediately noticed the bottom tiles in the stand-up shower were, shall we say, mushy. I knew this was going to be my first big project. I also knew I needed to do it right the first time, so I started doing a lot of research on and off line. This is some of what I learned regarding building waterproof shower walls with ceramic or porcelain tile.

Most of what I've learned is from Jaz and Bud right here. Thanks guys. :thumbsup:

Fact #1. Water or moisture in your wall cavity is a very bad thing. It can cause water damage, rot and, mold. 

Fact #2. Tile (ceramic or porcelain) is not waterproof. It will absorb water. How much will depend on how highly glazed the surface is, along with the type of tile.

Fact #3. Standard grout (sanded or unsanded) is not waterproof. Sealing grout does not make it waterproof, it just makes it easier to clean/less likely to stain.

Fact #4. Thinset is not waterproof.

More facts: 1/2" cement board (CBU) is generally used on walls underneath tile. It is used because it is not affected by water. If you soak any type of gypsum product (drywall, moisture resistant drywall, etc.) in water, you will end up with a handful of mush. With one exception I’ll get to later, drywall, even moisture resistant is NOT allowed in a tiled shower or wet area. 
If you soak CBU in water, once it dries it will be basically as good as new. This is NOT the same as being waterproof. Moisture can and will wick through it. If someone claims the CBU product they recommend is waterproof go to the manufacturers website for the final word.


So far everything I’ve talked about is not waterproof. So what is?

My research shows four ways to waterproof tiled walls. This is offered as a very brief overview. Any method requires more research regarding correct fasteners, dealing with seams, etc.

1) Heavy mil plastic. 
A sheet of heavy mil plastic (or similar product) between the CBU and studs is an accepted method. I’ve never understood it though. Although it may keep water from direct contact with the studs, it seems to me any moisture is still trapped in the wall cavity. Maybe I’m missing something here.

2) Roll or brush on waterproofing. 
There are products that can be brushed or rolled on the CBU before tiling. Hydroban is probably the best although there are others out there. Redgard and Laticrete 9235 are a couple of others. Mapei makes some also. This is the method I used. Effective and cost efficient. 

3) Kerdi.
This is a waterproof flocked sheet product that is applied to walls using thinset before tiling. This is arguably the best way to waterproof. This is the only exception to the no drywall rule. 
FWIW, if you’re doing a project that requires inspections, it wouldn’t be a bad idea to run this past your inspector so he/she doesn’t question why you’re putting up drywall in a shower. 
Cost can be an issue here, especially if you add in their drain and shower pan systems. Google Schluter-kerdi for their website with more information and instructions. 

4) Kerdi-board (or similar product).
This is a relatively new product. Use it instead of CBU. Apparently it is a type of rigid foam board with a waterpoof side. From what I’ve read it is very lightweight and much easier to cut and work with than CBU. When I did my shower two years ago I ruled it out because the nearest place that had anything comparable was 80 miles away, so price and availability may still be an issue. 

Final word, don’t think if one is good, two is better. You want to choose and use only one method, otherwise you risk trapping moisture between the two. Not a good thing.


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## Blondesense

Oh yeah. When I did my shower I didn't want a tiled shower floor so I decided to keep the existing fiberglass receptor.
For anyone planning a tiled floor this is a good starting place.

http://www.ontariotile.com/preslope.html


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## Jim F

I used the plastic sheet behind the CBU for my first tub surround project. I'm thinking about using Redguard or HydroBan on the CBU in lieu of the plastic on the studs for my next project. 

HydroBan for sure if it turns into a shower product. The only reason I would consider Redguard for the tub is the cost of the HydroBan. I would still use a shower receptor rather that trying to build a mud floor myself, probably one of Kohler's cast iron receptors.


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## cleveman

Densshield?


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## Blondesense

cleveman said:


> Densshield?


I googled them, but all I got was a bunch of PDF files. My computer does not like PDF files.
I think they are a "moisture resistant" CBU, but anyone interested should do a bit of research themselves.


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## IntexInspector

I always use either cement board with Kerdi or the new Kerdi board.


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## pwgsx

Use cement board with Hydroban or Redguard.


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## scottyh63

Can you use "red guard" with pre-mix tile morter?
1.) im using hardiebacker cement boards already up.
2.) Can i get away with not using red guard and just use water proof sealant in the seams..and just put up morter and tile, it seems that when i took these walls down in the shower stall it was orig. just 1/2 inch sheetrock boards and taping....House is over 35yrs old..


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## elg

I used Wedi board. It's perhaps a bit pricey, but it goes in easily and seems to work well. It's rated for steam rooms, so I guess it's good. For the floor I used a sheet membrane from Noble. It's like Kerdi, but thicker. Since thinset binds directly to both the Noble and the Wedi, the whole thing goes in very easily. The Wedi is far lighter than cement board, and it cuts and snaps more easily than drywall. I found it extremely convenient to work with. I took the Noble membrane up six inches behind the Wedi, so I feel very confident that no water is getting behind them.


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## pwgsx

scottyh63 said:


> Can you use "red guard" with pre-mix tile morter?
> 1.) im using hardiebacker cement boards already up.
> 2.) Can i get away with not using red guard and just use water proof sealant in the seams..and just put up morter and tile, it seems that when i took these walls down in the shower stall it was orig. just 1/2 inch sheetrock boards and taping....House is over 35yrs old..


 
#2 I wouldnt. You want to tape the seams using motar on the cement board, then redguard everything to thickness specs. On mine I used Hydroban on walls and floor and loved how easy it was to use. Give it a try, you wont be sorry.

What are you doing for the shower floor? This also needs to be done correctly.....


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## MarkusAIC

Durock, densshield/densarmor are good affordable products
Kerdi/Schluter membranes are the way to go if you can afford it
Drywall and greenboard drywall are NOT rated for wet locations


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## Blondesense

Kate, this is the how-to section. If you have a question you are better off starting your own thread in one of the discussion forums.

Pics are always a plus.


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## amodoko

Great post blondesense Just wanted to add a quick comment on this thread for others that are going to waterproof their shower/tub. In your original post, under the Heavy mil plastic option, you had said this:

_"A sheet of heavy mil plastic (or similar product) between the CBU and studs is an accepted method. I’ve never understood it though. Although it may keep water from direct contact with the studs, it seems to me any moisture is still trapped in the wall cavity. Maybe I’m missing something here."_

I had the same question when I did my shower, and it took a bit of researching to figure out that you need to allow openings in your caulking for weep holes, to allow the trapped moisture to have a place to go when it builds up behind your tiles. Here is a link to an image of a weep hole:

http://floorelf.com/wp-content/uploads/2010/11/CIMG5404-585x438.jpg

I believe they are recommended even for the other water proofing methods (such as Redgard, etc), but are strongly recommended for the heavy mil option. This will then solve the problem of the trapped moisture. 

Here is a link that discusses everything about weep holes from an expert:

http://floorelf.com/location-of-weep-holes-in-tile-installations

This way, when water builds up in the wall cavity, it will simply drain out into your shower floor or tub and you will have less chance of moisture ending up in place you don't want.


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## ohman

Thanks so much for this wonderful thread. I really appreciate that (especially amodoko about "weep hole" and Blondesense for the original post).
I have some related questions that I hope that people won't mind me to ask them here and hope it can add to the discussion of this thread.

We have a "bath" that we decided to convert it into a shower. Here are the before and after photo:
BEFORE:


AFTER: (by the way the heat register was sealed later and in this photo he had not grouted yet)


I did notice the tile contractor left some "weep holes" and I almost wanted to caulk these holes myself. I'm glad that I did not do that and this totally make sense for me now (for the trapped moisture to come out). However, I did notice that he just put up the CBU and then directly put up the tiles without using Hydroban or Redgard. When I politely asked him whether this would be good enough for waterproof, he told me not to worry and if we found any leaking problems later he will be responsible for the damages later. At that point I just kept my mouth shut as I didn't want to piss him off (after all he should be the professional and knows what he is doing, and not me telling him what's the right thing to do). My questions:

1. Since we only put up new tiles on the wall (and not the floor, the bottom remain to be the bathtub), and we also put in a really good bathroom ceiling fan (Panasonic FV-11VHL2 with 110 CFM), do you think we should be OK for any potential water/moisture problem in the future (if we do turn on the fan every time when we take a shower)?

2. If this is NOT OK, given that the contractor already finished the job, is there a good way to remedy the situation? Thanks!


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## pwgsx

O MAN........you got a wall with mold ready to grow.


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## amodoko

Hey ohman, thanks for the "thank you" on the weep holes. It took me a long time to find that information so I thought it would be helpful for others. If the bath tub was going to just be a bath tub that you lay in without a shower head, it would definitely have been okay.

But since you are turning this into a shower with a shower head close to the ceiling, there needs to be some form of waterproofing based on what the shower experts say. Otherwise, over time, mold will form I believe, but you just won't see most of it since it will be hidden behind walls. 

Having said that, I once spoke to a man online that worked on building houses (he mostly did trim but is a very handy guy) and when he redid his own shower he just put up CBU and tiled as well (he posted this on youtube, here is the link: http://www.youtube.com/watch?v=n8dAtp0kVhY&feature=plcp ) . He even said that was how they did it in the houses they worked on and he felt that would be enough for waterproofing. I can tell you in advance that most experts on this forum would disagree with him and tell you that you do need some waterproofing (since tile, CBU, and thinset are not waterproof). 

So I don't know from long term experience how worried you should be, but the short answer is that your worker did leave an important step out of the process and should have waterproofed it if there will be a shower head installed.

And the remedy for this... I really don't know other than removing the tile, then adding Redgard/Hydroban (or some other waterproofing method) to the CBU, then retiling. I know that sucks to hear, but if there is another way to fix this, the experts in the plumbing/remodeling section will know best. 

And lastly, I would probably post this question in the plumbing or remodeling forum for advice rather than this thread. You will get more information there, plus blondesense wanted to keep this thread free of questions and keep it more as an informative how-to section.


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## KateSolomon

Hello Everybody,


Last I had bought a new house but did not pay attention to waterproofing my bathroom tiles as a result it got molded any ways I contacted some people and they brought things in right order. I hope I would have read this article last year, then things would have been really different. Thanks for posting up such an important topic, I will make use of these tips in my kids bathroom whenever I get it remodeled.
:thumbup1:


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## cclements2

*how to water proof your job*

if you truly want to water proof your job... you need to start with products 
that are in themselves truly water proof...

look up wedi products.. these boards are completely water proof and make tiling a snap... any DIY can master the art


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## Nailbags

I know this is a old post. But before one lays the first tile. To water proof a tile shower the best product to use is Hydro ban from Laticrete. yes it is expensive but it is the best on the market.


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## jeffnc

Blondesense said:


> Kate, this is the how-to section. If you have a question you are better off starting your own thread in one of the discussion forums.


I don't see any questions she's asking in her post - just information.

I use exclusively Kerdi over drywall. I'm sure you can get the other methods to work too, but this is a niche that can distinguish me from all the "me too" guys. Of course, it also distinguishes me from the "me too" guys who don't waterproof at all


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## GB Greg

I have to add a vote for wedi. Especially for a DIYer. While the system may be more expensive than other options, it has fewer components, fewer steps, and pretty darn simple to work with. Not to mention that it's 1/2" thick and 100% waterproof versus sheet membranes and liquids at 40mil (that's 0.004"). 

Understand what you're putting in your shower system. If you're intent on doing it right the first time; do your homework. 

Don't just consider the attributes of a single component, consider that components effect on your other components. Example: Tile manufacturer recommends using a specific type of adhesive but the backer manufacturer recommends something different. Which adhesive do you use? What happens if something fails?

I have a question about the orange stuff: Where the material has seams and corners, you're supposed to use non-modified thin-set (not waterproof) to adhere the sealing strip over the joints, right? Seems counterintuitive to bond two waterproof products together with a product that's not waterproof. Am I missing something?

Remember, if you're a DIYer (which we all are) know what you're getting yourself in to before you start. Do your research, make a plan and stick to it.


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## Bud Cline

GB Greg said:


> I have a question about the orange stuff: Where the material has seams and corners, you're supposed to use non-modified thin-set (not waterproof) to adhere the sealing strip over the joints, right? Seems counterintuitive to bond two waterproof products together with a product that's not waterproof. Am I missing something?


Lapping of the membrane is required when using thinset to join the two, a minimum two-inch overlap is the requirement.

KERDI-Fix can also be used but the minimum two-inch overlap is still required.

Modified thinset is also permissible.


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## jeffnc

GB Greg said:


> I have a question about the orange stuff: Where the material has seams and corners, you're supposed to use non-modified thin-set (not waterproof) to adhere the sealing strip over the joints, right? Seems counterintuitive to bond two waterproof products together with a product that's not waterproof. Am I missing something?


That's a good question, because thinset is not waterproof. The overlap recommended by Schluter does not make the Kerdi act like roof shingles to shed water (for example, it doesn't matter which direction they are overlapped.) The answer is that the little fibers in the Kerdi penetrate or extend into the wet thinset and break the wicking property of water so water can't penetrate. This is why it's important to mix the thinset a bit on the wet side but most importantly install the Kerdi while the thinset is fresh and wet and press the membranes together well and squeeze out excessive thinset as directed. Actually a 1/4" inch overlap would work, but Schluter specifies 2" to be on the safe side.


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