Shower Tile Basics or Shower Tile 101

by Roger

I get a LOT of questions from my readers about basic shower construction. I understand that my readers don’t consider this stuff basic and there’s no problem with that. The problem is that I end up answering the same questions over and over and over… So, to save what very little is left of my sanity (which is a number roughly equivalent to absolute zero) I will cover some basic things here so I can simply reply ‘read this’.

If you’ve been channeled to this page by one of my smart-ass comments please take no offense to it, I’m here to help. Please understand that I currently have over 12,000 comments (questions) on this site (seriously) which I’ve answered – every one of them. I’m just trying to make your life (mine) easier.  I will continue to answer every question I’m asked, I’m just super cool like that. 8) If, after reading through this, you still have questions feel free to ask them in the comments below.

You can also download my shower waterproofing manual which should answer a lot of questions and cover basic techniques and methods you may be confused about. Go ahead, it’s free.  So without further ado (doesn’t even look like a word, does it?) let’s get on with it. (For all my readers who feel the need to correct me: I KNOW it’s actually ‘adieu’ – I was being facetious. Thanks. :D )

Leaks

First and foremost – tile is not waterproof. Grout is not waterproof. Adding sealer to your tile or stone will not make it waterproof. Your shower should be completely waterproof before a box of tile is even opened! No matter which waterproofing method you choose, proper substrate preparation is the only thing that will make your shower waterproof.

If you have a leak in your shower – stop using it immediately if at all possible. If that is not possible (it’s your only shower) have the shower repaired – immediately. If you see water leaking it is likely not nearly as much water as you don’t see leaking into your wall cavity and structural framing. By the time you ‘see’ most leaks the framing is normally already considerably compromised.

No, there is nothing you can put over your tile to make your shower waterproof if you have a leak – not even sealer. A tile or stone sealer is made to make your tile and grout stain-resistant, not waterproof. It does this by sealing the pores of the tile and stone to slow (NOT STOP) the absorption of liquid and prevent staining. It only means you have more time to clean up the spilled red wine cherry kool-aid before it stains anything.

Substrates

Drywall is not an acceptable substrate for your shower unless you are using Schluter Kerdi waterproofing membrane – that’s it. Cement backerboards are the standard and there are also other products such as waterproofed, gypsum based boards like Denshield and waterproofed, foam-based sheets like wedi or kerdi board.

Cement backerboards are not waterproof. They are water stable, which simply means that they will not swell or disintegrate when exposed to moisture or water – they won’t change size. But they are just like your driveway, they will soak in water, hold water, and dry out, just like your driveway when it rains. If using backerboards there needs to be a waterproof membrane utilized as well.

Membranes

If you are using a topical waterproofing membrane such as a liquid like redgard or hydroban, or a sheet like kerdi, do not use a moisture or vapor barrier behind your substrate. If you have a vapor or moisture barrier behind your substrate do not use a topical membrane on the front of it. This combination creates two waterproof barriers with your substrate sandwiched between them. any vapor or moisture trapped between them has absolutely no way to dissipate. This is lovingly referred to as a ‘mold sandwich’. It is not tasty. Use either a moisture or vapor barrier behind your substrate or a topical membrane on the face of it. One or the other – never both.

With that said, if you want to use a topical liquid such as redgard on the seams of your backerboard, after you tape and mud them, you can do so without problems. If your moisture barrier and backerboards are properly installed there is no real reason to do so – but if it will help you sleep at night go ahead and do it.

If you are using a topical membrane and you have an exterior wall with either plastic facing or kraft paper facing you need to cut slits into that facing before installing your substrate. If you do not it will create the aforementioned mold sandwich. Give moisture or vapor somewhere to dissipate.

Shower-tub transitions

There should be a gap between your tub or acrylic shower base and the bottom of your backerboard. If you are using a traditional barrier waterproofing method you do not need to do anything with this gap. Do not fill it with silicone! This will trap moisture running down your barrier and it will have nowhere to go. If you are using a topical method you can fill it with silicone if you want. If you are using liquid you should fill it with silicone. This creates a waterproof plane between your membrane and the tub or base so water or moisture ends up in the drain rather than in your wall.

When you tile you can tile right over that gap. You should not fill this gap with thinset behind the tile – it will crack due to movement. Your wall and tub or base will expand and contract at different rates – it will crack any cement-based product you place between the two. This includes thinset as well as grout. You do not need a solid backing behind your tile over this gap – it should be less than 1″ wide. You shouldn’t normally be walking on that tile in that particular spot. Yes, it can just hang there.

Grout

If your grout is cracking it is due to movement 99.9% of the time. Type ‘cracking’ into the search box up there and you’ll find in-depth explanations for your viewing pleasure.

If you have white, or lighter than normal grout when you’re finished grouting it may be efflorescence. This is mainly due to minerals in the water being left on the surface of the grout when the water evaporates. It is usually indicative of either incorrectly mixed grout or using too much water while cleaning the grout – not wringing out your sponge enough. This is normally only on the surface of your grout. Scratch the very top layer of your grout in an inconspicuous spot with your fingernail. If you have the correct, or at least a darker, color beneath the surface that is the likely cause. The easiest, quickest fix, provided it is only the very top layer, is to get some drywall sanding sponges and go over the grout lines very lightly. Just like burnt toast – scrape it to the color you like.

Corners and changes-of-plane

Caulk. :D

Disagree with me?

Like any other website I get my fair share of people who disagree with my methods or techniques – it really doesn’t bother me. I am more than willing to have a civilized, intelligent conversation about anything tile related. If, however, you simply attack me personally and act like an uncivilized ass I will call you on it – and not in a nice way. I write this blog in a particular manner, it does not mean that I take my profession lightly – I most certainly do not. If I wanted to be a pompous bastard I currently have 19 letters I can place after my name – all tile related. But I’m not a pompous bastard – you can just call me Roger. :D

If you are a contractor with a customer who has come here for information and I’ve told them you’re wrong – realize that the extent of my knowledge of that particular project is limited to what I’m told by your customer. It does not mean that I am ‘out to get you’ or anything of the sort. I normally limit my replies to those situations by stating the current TCNA and/or ANSI standards pertaining to what I’m told. If you disagree – please let me know in a civil manner, If you’re correct I’ll back it up – I do this everyday, too! If you’re an asshole about it expect the same in return (It’s the comment by ‘Kanela’ with the bold print before it) – and please have a thesaurus handy to interpret my reply – I’m a very well educated asshole.

That’s it for now. I will likely add to this post on a regular basis. If there is anything I’ve caused confusion with please, for the love of God, let me know. I can change this page since, you know, it’s my website and all. If you have any questions at all please ask them below – I’ll answer, really. :D

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Nick

Hey Roger
Should I have a gap between my pebble mosaic river rock shower floor and the shower wall tiles, and if so how big of a gap? Do to the variation in the sizes of my river rocks I have about 3/8 of a gap in the corners when I put my bottom row wall tile on. Should it just be set down right on top of the rocks or should I fill it will silicone

Reply

Roger

Hi Nick,

With rounded top pebbles you should set the walls first, then cut the pebbles to the wall with a 1/16″ – 1/8″ gap between them. If your floor is already set I would set the tile directly on them, it will only touch the highest point, then silicone the gap.

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Nick

Hey Roger
When tiling the shower wall and the shower curb how should this process go do i set the wall tile around the curb first and leave a gap or butt it directly up to it, then tile the curb and leave my 1/8 gap from the wall tile? Or should I do the curb first and butt it directly against the wall or leave a gap?

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Roger

Hi Nick,

I do the curb first, leaving 1/8″-1/4″ gap on the ends, then run the wall tile down to the curb, leaving 1/16″ gap between the wall tile and curb tile.

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Jackie

Hi, Roger.

I have an older shower/tub enclosure. Over the past 2 weeks, I’ve noticed the ahower stays wet all day–not just at the bottom but on the walls and fixtures in the shower, as well. It always looks like a shower has just been run, yet nothing else appears different. I see no evidence of a leak. Any suggestions?

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Roger

Hi Jackie,

Go to the transition between the tub and tiled wall and remove (what should be silicone, but may be grout) whatever is in there about an inch long. If you see water run out of the wall once you do that you just need to install weep holes.

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Sam

Roger,

Got your Waterproofing Manual which by the way is great. I’m using the Kerdi on my tub, but I realized that I installed all 3 of my Kerdi valve seals backwards (the wide protruding side is on the outside). I’m thinking I can salvage this boneheaded move by simply trimming the rubber on the seals back flush to the plane of the tile once installed. Alternatively, I can attempt to remove the backward installed seals and reinstall new ones correctly. Your advice would be appreciated.

Thanks!
Bonehead Sam. :bonk:

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Roger

Hi Sam,

Just trim it to the tile when you’re done. I’ve done that a lot too. :)

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Jody

Hi Roger… you seem like an elf who knows his business, and if you’re willing I need some advice.

I have a small, (5″ x 90″) backsplash behind my kitchen sink that I need to set some slate tile on. The surface is a well supported 1/2″ plywood. I happen to have some KERDI membrane left over from a shower project and thought to mount that behind the tiles. My issue is that this plywood has a good amount of silicone on it from what was there before. I scraped away what I was able, but obviously some of it absorbed and I’m worried my membrane won’t adhere properly if I try to go on top with modified thin-set. I know I should probably just by a thin KERDI board, but I’m trying to use what I have to keep the hubby sane, and am trying not to eat up too much space behind my faucet.

My nutty idea was to thinly spread KERDI-fix and than adhere the membrane with a brayer?… I know, probably a desperate attempt.

Wondering how the elf would approach this project?

Thanks so much for you time. It’s greatly appreciated.

Jody

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Roger

Hi Jody,

Paint the plywood with killz, then install the kerdi as normal.

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Jody

Thank you sir. I’m on it!

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Jana

Nevermind I see you can’t

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Jana

Our master shower leaked into the closet and they found that tar paper was used initially and had disintegrated. We can’t afford to pay the deductible for insurance and the insurance had made us cash the check and it ended up being used in an emergency for car repairs. We can’t afford to tear the shower out and do another. Since the sheetrock in the closet is cut away is it possible to slide something underneath the shower?

Reply

Roger

Hi Jana,

Unfortunately there is no way to repair a leaking shower base without at least replacing the floor. The materials can be bought (depending on size) for under $40 normally, plus the price of the tile, which can be found on sale oftentimes if you’re not picky about the color or tile. If you can do that much I can work with you to walk you through it. Is that doable?

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Mindy

Hi, I’m doing a new small bath with a tiled shower with an acrylic floor pan and tiled floor with electric radiant heat using a Schluter Ditra-Heat Membrane. What do I do with the area between the shower pan and the tile floor? Should I run the membrane under the shower pan as well? Thanks!

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Roger

Hi Mindy,

No, install the pan first then run the membrane up to it.

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Andrew

Hello Roger,

My question is for a tub to backboard/tile transition when using a liquid topical membrane, like RedGard. You state that if a liquid membrane is being used, then the gap should be filled with silicone. I need some clarification on this. Are you stating that, prior to setting the tile, the 1/4″ gap between the backboard and tub lip should be filled with silicone, or just the 1/8″ gap between the tile and tub (like illustrated in the attached photo? Or both? Thanks!

FH09OCT_BACBOA_01

Reply

Roger

Hi Andrew,

Both, but your gap shouldn’t be that large. The backer should actually sit no more than about 1/16″ above it. But since it is you can get some backer rod (cylindrical foam) to stuff into that gap, then silicone the gap over it.

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Nick R

Hi Roger,

great website! I am attempting my first tile job and am in the prep stage now. I installed a new fiberglass tub to replace the old beat up metal one. The new tub is about 1/4″ to 3/8″shorter than the old one (60″ long vs 60.25 or 60.375″) so it does not butt all the way up to the studs on one wall. I will be using 1/2″ hardiboard which will make up for this difference, assuming that the walls are straight. If this wall is not straight then I will have other issues and will have to figure out how to shim the backerboard. I will be waterproofing with plastic sheeting.

In reading your other posts I understand that I should run my plastic sheeting so that it overhangs the lip of the tub. The hardiboard will stop 1/16″ above the lip of the tub (as shown below except I will maintain the distance at 1/16″). I will use silicone to adhere the plastic to the lip of the tub. I don’t need to worry about the small gap between the back of the tile and the lip of the tub.

Does all of this sound correct?

If I run my tile down to within 1/8″ of the tub as shown above, do I silicone around the bottom of the tiles (between the bottom of the tiles and the tub)? Or do I run grout along the bottom edge of the tiles? It seems like trying to get grout in there would be very difficult or impossible. However, if I put silicone there than any water that runs down the waterproofing will not be able to get back into the tub.

Thanks for the assistance!

Reply

Roger

Hi Nick,

Yes, that does all sound correct.You run silicone around the bottom of the tiles and leave weep holes to prevent that issue.

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KATHY CREASY

I am wanting to pebble around my Jacuzzi tub it is plywood frame how do I go about it I have hand picked the pebbles I want to use just unsure on how to waterproof the plywood before before starting the tileing process and help would be appreciated

Reply

Roger

Hi Kathy,

You need to put a proper substrate over the plywood. 1/4″ backerboard would be easiest. Then you can use any type of topical waterproofing on it. Or you can google ‘greenskin’, that will actually be your easiest and quickest option.

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John

I have a question about the bottom course of the shower walls. As you know a shower pan is not flat on the edges where the pan & wall meet. Do I need to cut the tiles to the contour of the pan or float them in a level straight line slightly hovering the pan? I know there will be a gap if I float it, but the gap in the middle of the pan edge is larger than the corner edges. When starting the course in the corner, the tiles are level. But towards the middle of the walls, the gap gets larger and tapers back to level to the opposite corner. I have to keep it level to wrap the enclosure, but the bottom course is really got me confused. Some wisdom & insightful knowledge would be a great help.

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Roger

Hi John,

I set them on the tub in the corners and shim them up as it runs to the center to maintain a level course. Just silicone that open area once it cures.

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John

So I keep a straight line going around the circumference of the shower, correct? What if there is a ¾” gap between the pan tile & wall tile? I know the pan should be level on the outer edge going around. Unfortunately the person who skimmed the mortar (not me) didn’t know proper procedure & towards the middle of the wall there’s a dip. My brother(the one who skimmed it) seems to think that cutting the tile to contour the dip will look better than what you suggested. I think it will look like s__t if I try to cut for the contour, because it will throw everything out of level. Also how big of a grout line is acceptable in the corners?

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Roger

Hi John,

A level line around the perimeter, yes. If you cut to the contour it WILL look like crap. Can you skim over the deck to straighten it out? I normally have between 1/16″ and 1/8″ in the corners.

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John

Sorry for the late reply. But unfortunately the pan has already been tiled. So adding/skimming mortar ain’t gonna work. I thought the same thing. I’m considering going with my initial thought and what the suggestion you made. So it doesn’t matter if there’s a gap as long as the bottom course is level wrapped around the perimeter? And fill the gap with silicone?

Reply

Roger

Yes.

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Mark

Nice article. But what about REPAIRS? As a handyman I get plenty of calls for loose for re-caulking, grouting, etc. Have a job now with several tiles falling off the wall. Grout failed. Water got in. Paper peeled off backing. Which looked like green board drywall. I would usually fix by removing the tiles. Cleaning. Treating with molded idea. Fans. And drying until moisture meter shows normal. Then reattach through tiles and grout. Plus skim coat grout the whole shower to fill in all the other holess and cracks. Plus re caulk allike joints too. Obviously the shower is jacked. But if someone’s selling or remodeling soon sometimes a few years is all they’re looking to buy. WHAT ABOUT SEALER? Or something on that damaged drywall before I reattach he tiles? There’s no paper left. It’s wet for now. But solid.

Reply

Roger

Hi Mark,

Did you read the article??? In the VERY FIRST subheading I stated, very clearly, that tile is NOT waterproof – that water WILL get behind it. Grout has NOTHING to do with it. Pinholes in grout, or missing grout, have NOTHING to do with it. So your premise that you ‘skim coat grout’ the entire shower has absolutely nothing to do with preventing water from penetrating the tile assembly.

I do not have any articles explaining repairs of any sort. The reason is simple: if I remove a tile and it has greenboard, or any other type of substrate behind it that has ‘paper’ coming off of it – the entire shower gets replaced or I don’t touch it. See, once I touch that shower in any type of capacity to ‘repair’ it – I OWN that shower, the entire thing. If (when, and it will) it leaks again, or more problems arise in that shower I am completely responsible for it.

To answer your specific questions: Water did not get in because the grout failed – the grout failed because tile was installed over an improperly waterproofed substrate – the grout had absolutely nothing to do with it. Grout failing is simply a symptom of a seriously larger problem. Drying until a moisture meter reads normal will only last until the shower is used – one time. Doing that may fix the aesthetic surface for a ‘few years’, but there are issues behind that tile, in the structural framing, that will be deteriorating over those few years that will not be seen until that jacked shower is torn out.

Sealer DOES NOT waterproof tile in any form at all. The ONLY approved waterproofing for use over drywall is schluter kerdi, and once the paper is gone it’s iffy, at best. And putting a temporary band-aid over a small area of an improperly waterproofed shower will do absolutely nothing at all to repair that shower. All it’s gonna do is make it look pretty for a little while because the underlying issue has been covered up.

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richard

hi
I am putting a tile shower in the basement. I have 2×4 walls on the outside wall of the house with fiberglass batt insulation with a vapour barrier. Can I put a kerdi wall right over top of the vapour barrier….or do I need to drywall first or????
Can you please advise me the correct way.
thanks …much appreciated

Reply

Roger

Hi Richard,

I’m unsure what you mean by a ‘kerdi wall’. You can put kerdi-board directly over it, or you can put cement backerboard or drywall over it with the kerdi membrane on top of it. You can not put kerdi directly over the barrier.

Reply

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