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.
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!
I put Hardie 500 backerboard on a section of wall with a seam. What do I us to seal the seam for painting? Do I need to put a sealer over the backerboard before painting. Is there a certain type of paint. This is in the bath with not affected by water. Could I put a rextured paint over it? Thank You
Hey Frank,
As long as it’s in the dry areas of the bathroom you can treat it just like drywall. Tape and mud the seams, use a primer on it and paint it with whichever type of paint you wish. Textured paint will be just fine.
Dear Roger,
If I have open studs to start with, go through the ideal process to waterproof and finish the walls of a tub/shower surround. On one side of the shower/ wall is a bedroom wall adjacent to the tub/shower wall. On the right side of the tub/shower surround is an outside wall with the exterior being brick, this is an old house built in 1970’s without insulation. There seems to be just an “insulation board” between the brick and the studs. I am thinking this: 1/2 inch Hardy backerboard screwed to the studs, fiberglass tape all seams, silicone between top of tub and bottom of hardy backerboard, then roll on lacticrete hyrdoband, install natural stone, grout, silicone caulk between wall corners abd top of tub and bottom of stone. Then sealer on grout and stone. My big confusion is what to put on bedroom wall adjacent to the showe: regular sheet rock, paperless sheet rock, or hardy board? Should you Hardy backer your whole bathroom?
Hey Michele,
Do you mean in the bedroom? If so, regular sheet rock will be fine back there. No moisture is going to get behind the hydroban. If you mean inside the shower (I don’t think so) then hardibacker board.
Yes, would you want to protect the bedroom wall by using a paperless sheetrock ? (the bedroom wall which is part of the bathroom center surround wall).
Can you list in order which is the best way to construct your bathrrom starting from the studs, there are many different experts whom suggest different methods.
1. studs
2. vapor barrier such as 6mm plastic (do you skip this step?)
3, hardy backerboard or cement board (which one is best)
4. mositure proofing product ( Lattic Crete Hydroban 9235 or Kerdi ?)
5. matar
6. tile or stone ( when do you seal stone/granite and with which product?)
If you are using the Laticrete product or the kerdi do not use a vapor barrier. Other than that your order is correct: Studs, hardibacker (is the best in my opinion), laticrete or kerdi, mortar then tile or stone.
I use Miracle Sealant’s 511 impregnator pro which should be available at HD or you can get it online.
Does the Miracle Sealant 511 have waterproof proerties or its just to prevent any stains?
No sealer has waterproof properties. Waterproof implies that water will not be able to penetrate past a certain layer – sealers don’t do that. For a sealer to work correctly it must have what is called ‘vapor transmission’ abilities. That is: it allows vapor and air to pass through the installation. This is required to allow your substrate, setting materials and grouts to ‘breathe’ and allow moisture to dissipate through the grout lines (as well as the tile to a very small extent). Sealer is only used as a stain repellant and to assist with easier cleaning. The 511 is no different.
It is IMPERATIVE that a homeowner do all their own research because the majority of laborers/ or so called “professionals” are not trustworthy or interesed in doing projects the correct/best way. They allso blame there deficits on other things. If I opperated like most of these characters all of my patients would be like MJ. HOMEOWNERS, its about be knowelgeable BEFORE YOU HIRE ANYONE. The key is to arm yourself with a wealth of knowledge beforehand. I am thankful for your blog and many more.
Hi Roger:
You are awesome. I have learned alot, but am in mid remodel, still got questions. I have hung a vapor barrier and backer board in the shower. I want to put in a niche, if I cut out the Backer Board and instal the niche, I will be cutting the vapor barrier. The if I waterproof the niche, wont the moisture still be able to seep through the baker and behind the niche where the vapor barrier is borken? Can I just add plastic and duct tape it? Paint the vapor barrier to the studs with an adhesive or redguard. Or what would you recommend? Thanks for the time you take to post this stuff, it is indispensable. You also have my fathers name, very cool.
Hi Sally,
You’re awesome too!
Yes, you are correct. When you cut the moisture barrier silicone the perimeter of the barrier to the back of the backerboard then waterproof your niche and paint the membrane out about two inches around the niche. Any moisture behind the wall will run down and around the silicone bead and by the time moisture gets to the backer from the niche it’ll be two inches away from that.
Hi Roger,
I am extremely ignorant when it comes to home improvements, and I was hoping you could help me with some questions. While showering in my husbands bath/shower (I was waiting for the caulk in my shower to dry) I noticed a few spaces between tile where grout was missing. After yelling at my husband for not noticing this (I wasn’t too mean) that our walls were going to be moldy and fall apart, I decided to demolish the entire bathroom and start new. Our house was built in 1971 and the tile had been up since. I carefully removed the tile from the 3 walls. There was a slight slight slight amount of mold in one tiny area, but it was on the adhesive and not the actual drywall. While removing the tile, some very thin layers came off the drywall. Otherwise, the wall is in really good shape. I know you are against tiling over drywall and will probably tell me to get rid of it, but before I do that I have a few questions:
1) Could I just put the Kerdi membrane over the greenboard, even if the first layer is missing. Could I sand it flat?
2) If I do remove the greenboard and install cement backer, how much of the drywall do I remove? Our ceilings are pretty high, so the tiles don’t go all the way to the ceiling. Should I cut the drywall a few inches above the tile line and replace all of that with cement backer? Then paint over the cement backer that won’t have tile on it?
So yes, I have no clue what I am doing and could use a little help! Thank you!!!
Hi Sara,
I will say that’s a bit of an overreaction for a couple of missing grout spots.
But hey – I’m all for it!
1. Yes, you can just kerdi right over what’s there. Yes, sand it flat.
2. Yes, you should go above the tile line if you replace it with backerboard. You can paint right over it if need be.
You have more of a clue than a LOT of people that come here and ask questions.
Hi Roger,
You’ve answered many of my questions and i haven’t started tiling yet. Thanks
1. Painting over backerboard is pretty rough or would you use some joint compound first as I have several spots where I have some exposed. The top of my shower has BB coming close to where the bullnose is going. I assume I wouldn’t have any problem as it wouldn’t come into contact with water.
2. I bought a corner marble shelf for one side of shower and the other has a niche..good instructions. I couldn’t find any info on your site for proper way to install this into shower.
3. My husband filled in one small 3 by 60″ area on floor with 1/4 BB to make it even with the rest of the floor. I bought Ditra for the installation for the whole floor, is that going to be a problem..putting it over the wood and BB. I had assumed he was going to fill it with a wood strip.
I appreciate it… thanks
Hi Janice,
1. You can use joint compound over the backer if you want. If you use the powdered kind that you mix with water then it won’t be affected by water. The pre-mixed stuff will not stand up to water.
2. It’s installed just like the ones built out of the wall tile. Read through this: Creating a corner shelf and it will explain how to install those.
3. It won’t be any problem at all placing ditra over both those substrates.
After reading one of your answers I would like your answer to work I’ve already done.I installed a new tub and on two sides there was a 1/2 inch gap that i filled with the greenboard.
I then installed tar paper over all three walls and installed Hardibacker over that. Will the tar paper keep moisture away from the greenboard or should i start over from scratch?
Thanks
Hey Eric,
While definitely not ideal the tar paper will keep moisture away from it. So no – you don’t need to start over. (Don’t do that again
)
I would like to know what 3 wall boards you recommend to put up around a tub with one outside wall, wall board that is water and mould resistant. A friend picked up Sheetrock Braand Humidex Gypsum panels reccommended by the Building Supplier. Not sure I like this and if you say it is okay, how do I install this. I would also like it to know which ever wall board I choose if it is to be hung horisontaly or vertically and can it be placed to come within a 1/4 inch of the tub surface for tiling. I realize I have to place a bead of caulking in here.
Hi Cindy,
If you are looking for a board to just screw to the studs and tile away look into denshield. I have never heard of humidex gypsum panels – and I can’t find any information online at all about it. I would be extremely nervous using that. Any board can be installed in any direction – makes no difference at all.
Hi Roger,
I am looking to install a Schluter shower system in a bathroom remodel. The studs are exposed and I’m ready to install the Hardibacker. Do I need a vapor barrier behind the Hardibacker or does the Schluter system take care of this?
Also, I have a plywood subfloor currently and I’m not sure if I should install Hardibacker over this to prepare for the Schulter foam tray. Which would you prefer to work with?
Thanks for any help you can give,
Eric
Thanks for your quick response. Another question about tiling, I have porcelain tile that is 10 by 16 and was thinking of using some glass tile in my design as a border. Problem: Can it be installed over the Kerdi and /or is that a special way to install it in a shower? The one I like the best is a 1 by 2 glass tile that is about 1/8th so I assume I can build up the mortar when I install.
Is there any thing I need to avoid or do?
Thanks again and love your web site
Hi Janice,
That depends on the particular glass. Some state that it can be installed over a topical membrane and some do not. The best thing to do is contact the manufacturer and ask what the limits are for that particular glass tile. You can build the inserts out with mortar, ditra, even 1/4″ cement board if needed.
Hi Roger
I have my poly up for the tiled shower surround I’m going to do! After I put of my backerboard.. Should I use kerdi for the seams in the backerboard
Is that allright?
Regards guv
When are you getting your own show! A half hour show on bathrooms would be better than a 1 hour show on decks lol!
Hi Roger,
Quick question. If I am using cement board around the tub, can I use the membrane water sealant? It’s pink I believe.
Or do I have to use Kerdi or some other type of vapor barrier?
Thank you!!!!
If you’re talking about redgard then yes, you can use it. If it’s something else that’s pink I dunno what it would be – so no.
thank you! can I use the same if i want to make a nook, and also what type of tile do you recommend on the floor and around the shower if im planning on using white wainscot on surrounding walls?
Hi Sara,
Yes, you can use redgard for any portion inside your shower – nooks included. The type of tile is entirely up to you.
Read through this and it should help you make an informed decision about the different tile types: Choosing the correct tile
I am so glad i have found this page. I have had my suspicions for a long time, that we have been completely duped by our so-called bathroom designer. He quoted us for a wet room, which he planned from scratch. He said he would be using aquaboard and ditra coupling for the floor. We had another trader on site, working on carpentry and sundry works. He witnessed this cowboy, putting up greenboard + kerakoll’s idrobouild tanking solution and Guintoflex tanking tape. All surfaces were apparently primed with primer a. Only one instead the six quoted sheets of aquaboard were used. Apparently, no dry wall screws were used, yet the bathroom “expert” insists that he did use these screws. However, had he not used passivated drywall screws, the normal type of screw would be fine, as they were completely encased within the tanking solution, meaning rusting could never occur. Is this true or am i really being lied to, as i suspect is the case? By the way, i read the comments regarding the greenboard. This cowboy trader claims ” green board , known for its water resistance and suitability for areas of high humidity like bathrooms
Hi Judy,
Green board WAS known for it’s water resistant properties – five years ago. Since then it has been discovered to actually feed mold. It is no longer an approved substrate in any wet area – anywhere.
I’m familiar with the aquaboard – and it works well, however, I am not familiar at all with either of the other two products you’ve mentioned. That makes me think that they are not proper for that particular application – I’m usually VERY familiar with all approved products. I could be wrong, but I don’t think so. I think he’s using products not made for the application in which he’s using them.
Roger,
You sound quite knowledgable.
I am about to waterproof and tile a custom built shower. I was thinking about using the Kerdi, (cost is definelty an issue for me) but the experts at the tile store (this store has been in business for over 70 years, has 10 locations throughout MD/VA/DC) informed me of a less expenisive alternative and I wanted to bounce it off of you.
First a couple things about the construction:
I have pressure treated framing behind the green gypsum and have a 40 mil PVC liner above a pre-sloped floor. The pre-sloped shower floor is constucted from 3/4″ Arauco plywood on top of a 3/4″ OSB sub-floor. The drain is a standard type with a bolted flange with weep holes. I pre-sloped the floor so I would not have to create a mud bed for load considerations. I plan on using the mesh-backed river stone for the floor of the shower, and typical ceramic tile for the walls and the bench seat.
My questions are:
1) Have you ever worked with MAPEI AquaDefense?
2) Whether I use the Kerdi or the AquaDefense, is the greenboard an appropriate substrate behind either waterproofing system? I only ask because on the Schluter website they say it is an appropriate substrate. But, you have stated in your posts above that the greenboard belongs nowhere near a shower.
3) The green gypsum board was painted (with semi-gloss) down past where I plan to tile. Will the AquaDefense adhere to the latex paint or do I need to ‘scuff’ the surface for it to adhere, or maybe apply a flat primer like ZEP? Same question for the thinset that I would use to install the Kerdi membrane — Do I need to ‘scuff’ the walls for the thinset to adhere to the gypsum so the membrane will adhere to the walls?
4) If I go with the AquaDefense should I use a membrane in the coves and corners and around the drain and showerheads and valves?
5) Is there a special grout or grout sealer that I should use with the mesh-backed river stone floor? Any special advice for that kind of flooring option?
Thank You in Advance…
A Serious DIY’er — Kyle
Hey Kyle,
Not really knowledgeable, but I fake it pretty well.
1. Yes, it works well
2. Gypsum-based backer is only an acceptable substrate beneath kerdi – that’s it – really. It is not acceptable under ANY liquid membrane. The greenboard limitation is due to US plumbing and building codes – it is no longer an acceptable substrate in any wet area. Chose which rule you want to break – that’s what it comes down to.
3. Anything you place over a painted surface requires the paint to be scuffed up to create a surface the adhesive can grab.
4. AquaDefense requires fabric reinforcement at all changes of plane and around the drain when used as the floor membrane – so yes.
5. Any good impregnating sealer will work well. The river stones will use a LOT of grout – I mean A LOT! Plan for that. And make sure you get full coverage under the entire bottom half of every stone. Any voids will lead to problems due to the round shape on the bottom – voids can create a cantilever affect and pop you rocks off. (That didn’t sound right, did it?)
Roger,
Thank you so much for all your help for all of us!
A few quick questions.
1) Should I use HydroBan on top of the mud bed? I have laid a mortar bed with quick-float, a universal center ring for my square drain, and a weep hole protector on top of a PVC liner. I am using a regular clamping type bolt down drain. I bought 2 gallons of HyrdroBan and have at least 2/3 of a gallon left— don’t want it all to go to waste. It’s a big shower 8’x4′.
2) Do you know of a good sealer for my river stone pebble floor? I don’t want it to look glazed. I don’t want it to change color very much at all.
3) When I set my river stone pebble mosaic, should I use extra Thin-set, or should i try to fill the rounded undersides between the stones with the grout?
4) Do you prefer an epoxy grout for pebble mosaics? I was planning on using Spectra-Lock.
Thanks in advance,
Kyle
Hey Kyle,
1. No, you should not. It will create a moisture sandwich between two waterproof barriers.
2. Miracle sealant’s 511 impregnator pro is what I use. You can get it at home depot.
3. Use extra thinset to support the rounded undersides. Yes – it gets messy.
4. Yes, but it takes A LOT – like four times the square foot amount required for 3/16″ grout lines.
With a fear of sounding of sounding silly or old fashioned – can you please shed light on
the Float or Scratch method of a cementous material & lath on top of the waterproof backer
board that creates the base upon which to lay the tile. Thank you.
Basically the lath is attached mechanically (screws or staples) to the substrate and a thin layer of wet mud (sand, cement, lime) is coated onto it. Once that sets up a thicker layer, normally about 3/4″, of wet mud is floated over it and screeded flat. The scratch coat gives a uniform, solid base for the main layer to grab onto. Once cured it is the most solid, flat substrate you can create for a tile installation. The act of screeding it ensures a completely flat, uniform, level substrate for your tile.
Hi Roger: I am actually thinking of tiling our basement shower which we have been using for years. It is made of cement block. The previous owner painted it with a high gloss yellow (yuck) paint and I have since covered that with the blue pool paint. To no avail though because the paint is still coming off. Thus I have decided to tile. It already is a waterproof area so I am assuming that I can just tile over it???!!! I’m just not sure which tile is best for this……….ceramic or porcelain???
Hi Hank,
Unfortunately no, it isn’t waterproofed for tile. The blue ‘pool paint’ is … what? I’m not sure what product you’re describing there. If that’s what you believe to be waterproof then unless it’s Laticrete hydroban it isn’t a substrate suitable for tile – it won’t work. Porcelain is actually ceramic tile which is more dense (it has been fired twice) thus it absorbs less water. Porcelain is normally the best choice in a wet area.
Hi Roger,
Thanks for all the earlier advice, but one last question. When I was grouting the tile, I accidently took out too much grout and now it functional but looks aweful as it is between the accent tile and other tile at eye level. Can I just mix up some more and fill in the gap or do I have to cut some out and add. I have Kerdi underneath and don’t want to cut into it.
Thanks,
Lyndon
good question Lyndon……….I tiled my main floor bath floor years ago and since then it has developed some cracks. I have wondered for a while whether I can just mix up some more grout and top them off or do I have to cut it out and redo????? Can’t wait to see the reply to this one!!!!! Thanks for asking it!
Hank, if you have cracking in an existing installation it is likely due to movement in some manner. For your repair to last you’ll need to determine what is moving and repair that first – whether you scrape it out to 2/3 of the depth or not.
I’m just full of bad news for your tonight, aren’t I?
Roger, not bad news at all as doing it wrong would lead to worse news later down the road. As always thank you for your help and very fast responses. Lyndon
Hank, the saw that Roger refers to works great as I have used it before. Cheap, easy and fast.
You’ll need to remove the grout to at least 2/3 the depth of the tile. I would use a small hand-held grout saw. It will give you more control over the depth.
Hi there, I noticed we had some bubbles in our paint around our shower, I went to paint the bathroom (Im a painter by trade) so i popped the bubbles which i figured was caused by moisture and noticed that some of the tiles that surround the tub were popping off. It looks to me that all the previous owners had done was glued on the tiles to what it looks like to me semi gloss oil based paint. We have plaster walls. My question is what do I do now.. haha! Is there a membrane in which we can out on with out taking out the lathe plaster?
Hi Amie,
If you can get the tile out without damaging the plaster you can install kerdi over the plaster to waterproof your shower. If you do end up with small chunks coming out you can either install more plaster or just use thinset.
I am repkacing the tile in an old house. It appears to me that the material under the old shower surface is cement. It is grey and probably hand done. The house is an old adobe with all hand plaster on the walls. There is a thin layer of plaster on most of the cement but some came off with the old tile. Can I just put the new tile over this? Should I try to scrape more off ? All the loose stuff is off. I want to tile higher than the old tile. Can I tile on the old painted plaster or do I need to do something else to that part first? Thanks!
Hi Angelica,
Plaster is not very stable in a wet environment and may fall apart when wet. You’ll need to waterproof the shower in some manner. If you use a topical membrane over the plaster such as kerdi or redgard then you should be able to fill in any spots that come out with the tile with thinset and let it cure first, then waterproof and tile.
Roger, Thanks! But the layer of plaster is less than 1/8″. A bundh of the plaster came off whne I removed the former wall covering (floor linoleum). What about the cement under it. Isn’t that waterproof? Angelica
No, cement is not waterproof. Think about your driveway when it rains – it gets darker because it absorbs water. That cement in your wall will do the same. You’ll still need some type of waterproofing.
I’m convinced. Applied two gallons of redgard to the walls today. Scared my kids – thought we were painting the bathroom flamingo pink! Thanks!!
Hmmm. I just realized that I did not redgatd the narrow strip in. front of the bathtub sides (from the edge of the bathtub to the floor ). I used up all the redgard. Is ther something else I can use for this 1/2 sq ft area? Thanks again.
You can use redgard, kerdi, kerdi-band or any other topical waterproofing. It will be difficult to find only enough for that – you’ll need to buy a bit extra of something I’m sure.
Hi, We are getting ready to install porcelain tile above a 17″ tub all the wall up to the ceiling. Our double curved shower rid is 6″ wide, and we are wondering how far we can go out with the tile past the tub before it looks stupid. I don’t want the 6″ wide shower rod to be in the edge of the tile if we only go out 30″, because the shower curtain will not fall in front of the tub, and will not give us the extra space we need. If we go out to 34 or 36″, and the tub is only 30″ wide, should we continue down along side of the tub, since we have the same tile on the floor, and if so, I guess we would need backer board on the side of the tube on each side as well. The tub is not exactly straight, so would havea bigger grout line next to the tub, is that okay. Thanks.
Hi Nancy,
I usually go out three inches past the tub – the width of most bullnose tile, all the way to the floor. Yes, you should have backer all the way down to the floor outside the tub. Those spots always get soaked. Grout lines can vary if need be Sometimes you just have to do what needs to be done.
I am replacing the tile in my 60’s shower, it was originally done with cement over drywall. I currently have it down to the studs and have realized that the space from the studs to the edge of the tub is 1″ on one side but only 1/2″ on two sides. I guess I wasn’t really paying attention to the wall thickness when I was tearing it down. I suppose it didn’t matter to the person who originally put it in since they were cementing it by hand but it is a problem for me. I was planning on using 1/2″ greenboard and 1/4″ backerboard with 1/4″ tiles but now I am kind of confused. Any suggestions would be greatly appreciated.
Hey Kinsley,
I would add more to the face of the studs to bring them all out to 1/2″ from where you want them and use 1/2″ backerboard. Eliminate all the unneeded stuff like green board, which has no place anywhere near a shower. You can just use 1/2″ strips of wood over the studs on the 1″ side and use 1/2″ backer all the way around.
Thank you very much for the information, this is my first shower job and everyone kept telling me to use greenboard. Do I need to use some sort of moisture barrier behind the backer or on the studs? Thanks again.
Nevermind, apparently I am too much of a jackass to read the multiple paragraphs you have that answer that last one right above my question. Thanks again.
Oh, okay.
I’ll answer anyway – so there!
Greenboard is no longer an approved material in or around wet areas such as showers. You need either 4-6 mil plastic or 25# roofing felt (tar paper) behind your backerboard as a moisture barrier.
Another question regarding waterproofing, can you use kerdi membrane over wonderboard w/o the plastic. I thought I read somewhere you shouldn’t do both.
thanks again.
Love your site, wish I found it earlier
Hi Janice,
Yes you can. You just do not want to sandwich the backer between two waterproof membranes. It doesn’t leave vapor any place to dissipate and can lead to mold problems.
We are completely remodeling our bathroom (stripped down to studs and floor joists). We are trying to understand the best backer for tile in our shower. My brother mentioned that mudding the walls with wire (chicken, I suppose) to 3/4″ thick was one of the best ways to create a plumb and square backer for tile. I did not see that option on your list of backing methods. Can you tell me a bit more on mudding much like lath and plaster I guess?
Hey Stephen,
A mud shower is absolutely one of the best ways to build a shower. It is, however, not really a method that should be utilized by DIY’ers. Not that there aren’t people that can do it, just that most would have a tremendous amount of problems with it.
The wire should actually be steel lath installed onto the wall and scratch coated (which is a thin base layer of wet mud) then when cured, a full 3/4″ layer of wet mud is screeded onto the wall. The mixture is a ratio of 4:1:1/2 of sand/portland/lime mixed with water. It’s similar to deck mud but the lime makes it sticky. It takes a lot of practice and is a reasonably difficult skill to master. Not that it can’t be done, but it’s a lot of hard, heavy, exacting work.
Great information…thank you! I’ll check into the Schluter Kerdi system.
Btw – I am sure you hear it often, well done on sharing your expertise, your answers to others, and your great sense of humor. Hopefully, such praise will continue to keep the ego pumped and the superb responses coming.
Floor Elf,
Thanks for the information. We just had a tub and a tub surround installed. The tub surround is 6 feet in height. However, we planned to tile up the wall above the tub surround to the ceiling to prevent additional moisture getting to those parts when showering. Is it okay to put tile directly onto the drywall in this case?
Thanks in advance.
Hey Tiffany,
Yes, anything above the shower head isn’t a problem provided you don’t have a header across the front of the shower (a little wall coming down from the ceiling about 12′) which would retain steam and moisture up that high. If you don’t have that – have at it.
I appreciate the prompt response. Thanks!
Hello, this site is definitely very helpful. So here is my question:
I am to the tiling point in my shower. I have two different types of tile 16″ by 16″ for the shower walls and smaller tile for the shower floor. However I would like to use some of the tile I plan to put on the floor to put a decorative line in the middle of the shower wall. The problem I have is the tiles are a different thickness. Will this work out? How do I make them flush on the wall? Appreciate your comments very much.
Hi Myli,
There are a couple of ways to bring thinner tiles out further on the wall. The easiest is simply more thinset, you can add more thinset beneath the thinner ones to bring them out flush with the thicker tile. You can also use products such as ditra to build up the area beneath the thinner tiles.
Just wanted to say thank you. That is what I am going to do:)
Dear Floor Elf,
I am tiling my bathtub/shower. The drywall hanger hung Denshield up to but not over the tub lip (where it is screwed into studs) on two of the shower walls. The remaining shower wall is an exterior wall and here the denshield is 1/8″ recessed from the tub lip. On the advice of some tilers I know (I work on home improvement tv shows) I have mudded my exterior (recessed) wall with joint compound to smooth out the transition to the tub lip. I haven’t yet dealt with the other two walls where the denshield is 1/2″ proud of the tub lip. I’m about to start tiling.
Question 1: I didn’t put silicone on some of the seams of the denshield and now they are mudded over so how much of a problem is that? There is mesh tape though.
Question 2: I have been told that I can fill in the 1/2″ by 1″ gap on the two interior walls with thinset on tiling day but I continue to have doubts because this is where all the water will collect so I’ve been thinking of filling it in with mortar or thinset or a thin long strip of denshield. Not sure if mortar sticks to the tub material. What would you do?
Question 3: Since it is Denshield if I read you correctly, no need to paint on Redguard.
I am installing 12×24″ tiles laid horizontally and need as flat a substrate as possible or the tiles will rock.
Thanks for the witty posts. I’ve just finiished the mini series on Niches and I learned soooo much. How do you find the time?
Therese
Hi Therese,
You do realize that ‘joint compound’, the stuff used for drywall, will disintegrate when exposed to water long term, right? If that is indeed what you used to float that wall out then it needs to be removed. You can float it out with thinset which won’t be affected by water.
1. The seams which are mudded over need to be waterproofed – water will get into those seams through the thinset (or whatever you mudded it with). You can do this with redgard or a like product.
2. Do not fill the gap with thinset – it isn’t waterproof. It will simply take longer for water to get into your wall cavity – but it will get in there. If it is large enough for a strip of denshield then use that – with the appropriate silicone sealant. Mortar will not stick to the acrylic of the tub. The seam between the denshield and tub needs to be sealed with silicone.
3. There is no need to paint on redgard provided it is sealed at the seams and the bottom with silicone to create one solid waterproof barrier from the wall to the tub.
I find the time while I’m watching baseball, football or hockey.
Thank you, lucky for us you like sports. I was doubting the whole drywall mud skim coat.
I am thankful you answered my questions quickly, and I keep thinking of new ones, I have kerdi membrane over durock and was told to seal the bottom of kerdi over the cultured marble shower pan with kerdi fix. It overlaps about 1/8 to 1/4 ” . Q. Is this a better option than 100% silicone? I cannot find out what is in the kerdi fix, plus it costs 5 times as much. Thanks again for all your expertise. Have a great day!
Janice
Hey Janice,
It’s simply a different product. It’s a urethane-based (I think) caulking which cures hard rather than remaining soft. Either one will work just fine.
Roger,
Great site, thank you for the guidance. I am looking at replacing an existing shower wall and tile. If I am using a plastic vapor barrier and cement board, is there any kind of seal required between the seam created by the cement board and the drywall? How far from the shower do the vapor barrier and cement board need to extend? If I have textured walls, is it permissible to apply drywall mud directly to the cement board to blend the new wall with the old one? Thanks for your detailed description of the possible techniques.
Hey Erin,
The barrier and backerboard only need to be installed to the outside edge of the tub or shower. You can use fiberglass mesh tape (sold in the drywall section) to tape that seam then float it out with thinset. You can paint right over the thinset if needed. Thinset is normally the better product as it will not be negatively affected by water or moisture.
Sounds good. Does the vapor barrier need to be wrapped around the edges of the backer board or can it all be a flush sandwich arrangement? If I am installing a new tile wall in conjunction with an existing fiberglass tub, does the vapor barrier or backer board need to sit on the inside of the tub? I guess I’m worried that if water is going to penetrate the tile and grout, do you need to account for it draining back in to the tub vice into the wall. Do you recommend using thinset or mastic to attach the tiles to the walls? I’ve read about using both. Are there egregious disadvantages to one or the other? Thanks again.
The barrier and backer are just sandwiched up onto the wall, no wrapping required. The bottom of the barrier does need to overlap the tub flange and it then gets siliconed – the back of the barrier to the front of the lip. Always, always use thinset rather than mastic for a wet area such as a shower. Mastic may re-emulsify when exposed to water – thinset doesn’t.
Hi Roger,
Brilliant site, you’re giving me the courage to fix my bathroom the right way
I have two questions for you. First, a bit of background though…
Our house is an old house, but it was more or less fully rebuilt around 2004 by people who were handy, but not at everything. In particular, they made some very questionable design decisions in the bathroom. I recently went to fix what I thought was a small issue just outside the tub, and in doing so tile literally started falling off the wall. Turns out they did “flawed style” seals of some of the shower features, and mold was growing all over the greenboard that was behind it. I’ve now stripped out the greenboard and tiles from the shower. Now, for my questions:
1) The tile in the shower ran to about 6 feet above the floor. While I intend on having the new tile run slightly higher, it will not reach the ceiling as the design of the shower would make that look goofy. The greenboard above the shower that did not have tile attached to it is holding up fine — is there any reason I should replace this, and if so with what? I’d rather tear the walls down only once.
2) To confirm, when I put of the cement board I first put up the water seal — I’ll be using 4 mil plastic. Afterward, when attaching the cement board I use dry wall screws through both the cement board and the plastic to attach it, right? Is there any way to help waterproof the dry wall screws? A lot of the ones from the last design are now broken off in the wall.
Thanks! I’m a LOT more confident in what I’m doing thanks to this site!
Hey Dan,
As long as that greenboard is above the shower head and you don’t have a header across the top of the shower (which would trap vapor in the top of the shower) then you can leave it without worry. It is always better to replace everything inside of a shower but that won’t lead to any problems. You can always run the cement board all the way to the ceiling – you can paint right over it.
DO NOT! Use drywall screws to attach your backerboard. They are not waterproof and will fall apart (but you already know that – that’s why they’re broken off in the wall). Plus they won’t sink flush into the face of the backer. You need specialized backerboard screws which have little ‘teeth’ under the head which dig into the board to sink flush. They are waterproof – so you don’t need to worry about waterproofing them. And I know what you’re thinking
– no, screwing through the barrier will not cause water to run into your wall framing.
Awesome, thanks! The follow up question then is… Where would you find these backerboard screws with the little teeth? Perhaps it is just idiots that work at a couple hardware stores around here, but when I asked about them at two different stores, they suggested using something completely inappropriate. I didn’t see these, but admittedly I didn’t know exactly what I was looking for.
You should be able to find them at home depot or lowes over by the backerboard in both the tile section as well as where the drywall is (they usually have backer there also). They are normally called either ‘rock-on’ or ‘backer-on’.