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. 
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. 
)
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.
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.
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.
Roger!!!
Once again, love the site. You’ve been most helpful.
One more question – my new tub has 300 lbs. It’s sitting square and plumb with back wall, the gap is on the front and back. Can I just wedge shims in there to keep it from moving? my drywall is going to stick out further than the tub anyway, so I will still have the over hang for the first row of tiles, but obviously I dont’ want my tub shifting. I think this would work, but like most people on here, I only want to do this once! (Plus getting the tub in was a
!!!!)
Hey Derek,
Yes, you can use shims in there to wedge it in. No problem at all with that.
Hi Roger,
I have a problem and would like to hear your thoughts:
we are having leaking in our shower, I hired a plumber who said it wasn’t a plumbing issue (ie plugged the drain overnight), then hired a handyman who took of the bottom half of the wall directly behind the shower head. The handyman thinks we need to remove the grout on the bottom of the shower (edging facing the shower head wall) b/c of old water marks seen low on the wood, then higher up on the wood. The higher water marks seemed to match up with the edges of the shower.
If you think I need to remove and re-grout: can you advise sanded grout, miracle sealant 511 (tile is slate…which is not good for a shower correct?), calk?
Thankyou
Tanya
Hi Tanya,
The problem with leaking showers is not a problem with the tile or grout – it is always a problem with the substrate behind the tile. I’m unsure what you mean by the ‘old water marks seen low on the wood’ – do you have wood inside your shower or did you mean something or somewhere else? That particular part of your question is confusing me – not an uncommon occurrence, by the way.
Hi Roger,
We have access to the back of our shower wall (furnace room is adjacent to bathroom), and took off a piece of the the drywall. The wood beam close to the floor, running parallel to the cement floor has moisture. To repair a substrate….this means removing tile from the bottom of the shower…and, possibly a total repair of drains, shower well? Any advice welcome! Thankyou
Hi Tanya,
You want to remove your shower floor and walls up about two feet of the wall. After you make the repairs you’ll need to build yourself a whole brand new floor. Sounds like a good time for a complete shower.
Hello roger i just stumbled across your blog, and usually when i see a bunch of words and no pictures i just keep on moving but i will admit i did read and have also subscribed to your tips. now to my question…….. long story short – I bought a house gutted and reframed, one side of the wall is my bedroom, the other side is my shower wall in my bathroom. I want to tile the walls around my tub, and i also want to give it some thickness for sound, ( i do not want to hear the shower running or people in the bathroom while im in my bedroom) so i was thinking of doing, cement board, tape the seams, skim coat the wall w thinset, let it set up and apply the tiles w mastic. inbetween the wall i would use a styrofoam board insulation maybe 1 1/2″ – 2″ thick, and just simply sheetrock the bedroom side of the wall, also i no i skipped the moisture barrier step and thats where you come in. can you please tell me if this sounds like or is the proper way to go about this and what i need to do for a moisture barrier. Thanks so much
Hey Jerry,
You can add the stryofoam in the wall cavity without problems. You do need to add either a moisture barrier behind your backer in the shower or have a topical membrane over it. One has nothing to do with the other, your shower still needs to be waterproofed. You also need to use thinset to install your tile rather than mastic. Just build your shower as you normally would and add the styrofoam into the wall cavity from the bedroom side. It won’t affect the moisture barrier.
Hi Roger,
I’m sorry to be such a pest, but I want to make sure we get this right.
In shower/tub transitions section above, you advise stopping the cement board and tile backerboard above the tub flange–correct? I’m confused about what comes next, though. We are using the schluter/kerdi membrane product. I had thought we would use fibreglass tape and thinset in that gap and apply the kerdie over top of it before we put on our glazed ceramic wall tile. (We’re using 4 1/4 x 4 1/4″) However, now I’m just not sure.
This is a renovation. The previous installation had silicone between the where the wall stopped and the tub–and we had mould problems. As well, when we ripped off the plastic tub surround there was water damage all along the edges of the walls. So, I definitely see the point about the silicone/caulk. But, I’m afraid that without something there (like thinset and fiberglass tape) we will have the same problem when we go to caulk the edges of the tile to the tub.
But how close should the tile come to the edge of the tub, then?
Am I making sense?
The backer stops above the flange and the kerdi runs all the way down to the horizontal surface of the tub edge (the bottom of the flange). The BACK of the kerdi needs to be siliconed to the tub flange. That way no water gets up behind the kerdi on the wall and back into the wall cavity. The tile will then be installed down to within 1/8″ – 1/16″ from the top of the tub (nothing needs to be behind the tile in front of the flange – it’s only about 1″ or so) and that space should be filled with silicone.
Roger-
I am embarking on a virgin tile experience with installing a tub surround. For some unknown reason, the builders of our house installed regular drywall around a garden tub with a shower nozzle on the wall above. Of course, we never used it as a shower, but the bath was enough to cause mold and unsightly damage over the years.
We removed all of the damaged material. Added studs as needed. Installed 1/2″ backerboard and are now ready for the next step. I thought I needed to tape and mud the seams with thinset, let that dry, then apply a liquid membrane – 2 coats, let that dry and then begin to tile. Now, I have read in a couple of places that I should tape the seams and mud at the same time to keep from having “high points” from dried thin-set. Does my plan need to be altered? Do I need thin-set or modified thin-set for prep?
Your site is incredible! Thank you for sharing your knowledge.
Hi Geri,
If using a topical membrane like redgard you’ll need to tape and mud first, let that cure, then install your redgard. The other way around limits high points, but is only proper when the waterproofing is beneath the substrate. Both options are correct, just used for different waterproofing methods.
Roger,
You’re the Dave Barry of tile. That is about as useless as being the Champagne of Beers.
I’m not ragging, I understand your humor and appreciate your genuine advice. Speaking of which, I’d like to ask you for more advice, for free. Thank you.
I’m rebuilding my downstairs (2nd) shower from scratch. I’m done with the fun part of cutting 4″ concrete and using the jackhammer, and even putting in the 2×4 curb and pre-slope. Now is the not so fun part.
1. Before I found your site I used 3 PT 2×4 to make the curb b/c it made sense, like bringing up your old girlfriend when you’re drunk. Thanks to my inspirational work ethic, the curb has sat there for almost a year so I hope it has dried “enough.” And I’ve already poured the pre-slope up to the first 2×4. Can I leave the PT curb there? (I hope the answer is yes, b/c I’m probably just going to leave it anyway)
2. How does one go about forming the curb? I understand the lathe and concrete, but what about the shape and thickness? Radius or straight edge? Any special tools? How does the curb blend in with the backerboard? Like the bathtub? If you’re designing from scratch, how do you generally determine the curb width and height? (I’m asking lots of questions b/c I really want the next blog topic to be on this
)
3. This is an expansion on question 2 and reveals the depth of $#@% I’m currently in…
Hypothetically, let’s say someone I know has not installed the bathroom floor tile, or drywall, or ceiling yet wants to complete their bathroom in a month, what order should they prioritize things (besides finding a new house and drinking lots of beer)? What’s the logical order of installation? Ceiling, curb, floor, drywall, barrier + backerboard, liner, pan, then tile?
If you could make some more kindergarten style pictures of the curb, backerboard, liner, and pre-slope, etc. my wife would really appreciate it. We’re expecting a baby in 5 weeks and she’s not letting me out of the basement until I’m done with the shower.
Much Obliged,
Michael
Hey! I like Dave Barry.
1. Since you’re gonna leave it anyway – yes. I, however, would remove it. The pores in the PT wood are different than in regular kiln-dried lumber. While it may have reached an equilibrium with the concrete and surrounding area at present, once you cover it with waterproofing and tile it may act differently and start moving in ways you don’t want it to move. But since you’re gonna leave it…
2. The size, depth, and nearly everything having to do with the curb is normally dependent on the particular tile I’m using. If my bullnose pieces are 3″ wide I’ll sometimes make the curb 5 1/2″ wide (two tiles, grout line plus the width of the tile on each side of the curb). It’s easier to lay out tile in the shape of a curb and measure it – then form your curb to that size. I use flat trowels and various cement finishing tools to form the curb – a magnesium float is the one I use most. I’ll normally round the corners off a bit just for stability purposes while I’m working around it – square corners chip off easily. The ends of the curb simply butt right up to the backer on the walls. And I will write a post about this – in my free time. (Which currently is about zero).
3. I would put up all the walls and ceiling drywall and backers, paint, pan liner and curb, all the floor tile – shower and bath, then wall tile. And get as much sleep as you possibly can, ’cause in five weeks you’re gonna lose that luxury.
Ha! I thought you might.
And I like the Champagne of Beers, if I had to drink a cheap beer.
You’ve 2/3 converted me on Point 1. I’ll replace the top two 2×4, but I really don’t want to pull up the last one and greatly risk cracking the preslope and having to knock it all out and start over. (I know what you’re thinking, and yes I’ll send the pictures for your ‘Flawed’ page in a few months).
It’s fun to use that emoticon, but I hope it doesn’t come true.
Point 2 is surprisingly simple and very helpful, and Point 3 is clearly wise advice from someone with a lot of experience. I better start snoozing!
-Michael
Hi Roger,
Me again. New problem I’m having now – it seems most thinset/mortar companies don’t label it as “unmodified” when looking these up at the big box stores (HD and Lowes).
I’m unaware of any other suppliers in my area? There’s an ACE hardware I have to try yet. But is there anything you would recommend for use with the Kerdi? Anything I can purchase online? I’ve seen people recommend Laticrete and Kerabond, but not surprisingly, can’t find those at HD or Lowes.
Any suggestions?
Thanks,
Derek
Hey Derek,
Ordering online sometimes gets spendy with 50lb. bags of thinset. However, you can Google “Laticrete 317” (that’s what I use). You CAN use modified if you want – it works, really. I’ve used versabond from HD a lot. You will, however, void your Schluter warranty if you do that.
Hi again Roger,
Finally preparing the backerboard and have a some questions:
1. is it necessary to tape and use thin set if i’m using redgard for my tub/shower walls? i think you said i only need to if it makes me sleep better, but i want to be sure.
2. any particular type of thin set you recommend under the wall tile and/or floor tile?
3. do i need a different type of thin set for glass mosaic tiles than i do for ceramic subway tiles? can i use the same for both?
4. finally, in reference to doug’s questions of october 5 about the pipe holes in the backer board — what does it mean to leave the silicone proud of the wall? the holes for our pipes are a bit large. is it best to caulk, thin set & tape, redgard, then silicone followed by tile and finally silicone around the fixtures? i want to make sure it’s water tight.
as always, thank you.
–Deborah
Hi Deborah,
1. Yes, you need tape and thinset with redgard. You do not need it with sheet membranes like kerdi – although you can if it helps you sleep at night. With redgard you need it whether or not you have insomnia.
2. I prefer Laticrete 253 gold as my goto thinset. All laticrete thinsets are great. Versabond from customs, which is normally available at home depot, is also a good thinset. Mapei ultraflex II also. I could go on, but I won’t.
3. With most glass you’ll be fine with the same thinset. The exception is if the glass manufacturer requires or recommends something different – always follow their rules.
4. Leaving it proud just means that it sticks out from the wall – it’s on the face of it. That way when you place your tile over it the tile will squeeze the bead between it and the wall. You have the order correct.
Thanks Roger. Have a great evening.
Hi Roger,
I ripped out the caulking in new shower(Accucolr tec) and replaced with latisil silicone which was great to work with and came out fine. Have not taken shower yet(waiting a couple of days) and hope the silicone took, which is what I was worried about .Feels fine while dry but have had problems getting it to stick on other projects. but did extensive prepping(scrapping, silicone removers etc.-took a day) Thank you for all your help
Paul
1. What are some of your favorite techniques for tiling exterior corners?
2. Have you ever seen or made a good tiled access panel?
I’m building a steam sauna/shower and don’t feel confident yet with the above
thanks
-Rendall
Hey Rendall,
I normally use bullnose down the edge of corners to wrap outside corners with a nice finished transition. You can also miter the tiles (fairly difficult depending on the material) or use finish transition strip such as some of the Schluter profiles.
I make tiled access panels all the time. I’ll normally cut out the substrate the exact size of two or four installed tiles and set it in place then use color-matched silicone rather than grout around the perimeter of it. If needed the silicone can be cut out for access. There are also products which utilize hinges and magnets to accomplish the same thing. Just google ’tile access panels’ and you’ll find a lot of different options.
Roger,
I received 3 tubes of silicone latisil from rep.(new caulking from Factory). I have not used shower because as I stated earlier tec accucolor caulking rep said that acrylic silicone would not last on shower floor but would be okay on wall transitions.
Was going to take out floor area and replace with latisil but now I am wondering if I should take out all caulking and start fresh with latisil everywhere. I wish I knew this before because the acrylic silicone came out great but want to do this properly. Your thoughts? Would you rip it all out? Ifinished shower and have not used and this was my final step. Wish I had called rep. in beginning and they should state this on tube.
Thanks Roger.
Paul
Paul
Hey Dick,
I would remove all the other stuff and stick with the latasil everywhere.
So I installed this cool natural stone in the shower. THey are irregular shaped pieces of various size . But they are very porous. A medium gray when dry but jet black when wet. Should I seal these prior to grouting and then seal after I’ve grouted. I don’t want to “Stain” the rocks with the grout. And what kind of sealer do I use? I don’t want the stones to always appear wet. just natural when dry (and dark when wet if possible!) At the Home depot I saw a few different products– really expensive! Like $70 gallon! But was a bit confused as to there application. Do you have a type to suggest? Outside the stall in the bath there will be slate thats going to need to be sealed also but also want that to look natural and not “wet” when the sealer is cured to it.
Hey Steve,
What you want is a good impregnating sealer like Miracle Sealant’s 511 Impregnator. It should be available at HD and that’s likely the one you are talking about – good sealer is expensive and that is actually a very reasonable price. Most showers and bathrooms will take no more than maybe two quarts with a very porous stone. It will not change the natural look of your stone. The only sealers that do that are designated as ‘enhancing’ sealers.
Yes, seal it before grout and again after grouting.
Thanks, man! You REALLY Should be charging for this!
Don’t know if you can answer this or I need a plumbers opinion, but… Just about ready to tile the bathroom floor. The Toilet flange is not yet attached to the drain. Should I attach the flange to the hardibacker board and then tile up to it OR Install the tile and then put the flange on top of the tile (it’s Slate actually).
Hey Steve,
Install the flange after you install the slate. That’s the way it’s supposed to be anyway.
Roger,
I could use some grout tips. I tiled and then last night I grouted the area underneath where my vanity will be so that if and when I screwed up it would not be easily visable. I grouted about 12 square ft after about every 4 I stopped grouting and rung out the sponge to the point where I thought I would tear it and I wipped up all the excess then continued to the next 4 sqaure feet. After I thought I had clean it all up I kept getting a dry smear of grout over the tiles so I ended up wiping them down about 4 times over 2 hours and then even after that I had to do a dry buff to get the last bits up.
This morning there is a lot of color variation in the grout, some is the dark Chamois color ir is supposed to be while other parts are almost white and anywhere inbetween. It looks like I probably over cleaned the tiles maybe. After I use th float should I just let it sit there, use the sponge once and then dry buff the remaining after that rather than continuing to use the damp sponge?
Thank you,
Chris
Hey Chris,
What you have is efflorescence which can also show up if you clean the grout too soon. It needs to set up in the joints until it’s firm (about 15-20 minutes) before you clean it. If you do that, wring out the sponge well, go over it only once. Then wait about 45 minutes until the haze shows up and use a microfiber towel (wet or dry) to clean it once more. You just cleaned it too soon – patience Grasshoppa!
Thank you Roger, I completed the grouting yesterday and that turned out a lot better. Any suggestions on how to remove the efflorescence? Most of it will not be immediately visable but I would still rather take care of it.
Hey Chris,
A 5:1 mix of white vinegar and hot water should take care of it. Or you can use a drywall sanding sponge and lightly go over the lines – that will get rid of it too.
I made a mistake when I chose my grout color. I have a mixture of materials in my shower with those small random river rocks that come on a mesh on the floor and a 12″ strip down one wall and Limestone on the rest of the walls. So I needed Sanded Grout on the river rock and unsanded in the 1/8″ gaps between the limestone.
I shop at a place called Menards and they carry Mapei products. I bought the sanded grout first and didn’t check that they carried the color I chose in the unsanded grout. They don’t. I could either order and wait for 2-3 weeks to get that color or chose to use the premixed tintable stuff. The guy said it was epoxy-based but I wasn’t really paying attention to what that would mean.
It went in pretty well -although it was a pain to sponge clean the excess as the tint seemed to really want to stain my limestone but It worked out OK with extra work to get it back off and the limestone was well-sealed. But now I am reading that I am not supposed to seal this grout. I need to be able to seal the limestone again -right? I did seal it before installation and again before grouting (two coats each time), but I’ve got a bunch of sealer and planed on sealing it all over again along with the grout.
My question is, what will happen to the grout if I get sealer on it? Will it just not penetrate -or will it eat at the sealer? I’m not even sure if this grout is epoxy or not, it doesn’t say anywhere on the can and the guy I talked to at Mapei customer support knew even less about their products than I do (which isn’t much)
Did I screw up here? I should have just bought regular grout. How can I seal the natural stone tile without getting it on the grout?
Hey James,
Pre-mixed grouts are normally urethane-based. They have absolutely no epoxy in them at all and I really hate that people use that as a selling point. It’s extremely misleading. The combination of sealer and grout brands will determine whether or not you can use them together. Those grouts do not REQUIRE sealer – but it doesn’t necessarily mean you can’t use it. Put together a couple of scrap pieces of tile on a board and grout it then use the sealer on it to see if it will negatively affect it or not. It shouldn’t, but test it.
Thanks for the advice. Putting a couple scrap pieces on a board and testing the grout is a great idea. I think I’ll let the test bed sit a week or so to make sure it is good and cured before testing.
In the end I guess I am going to have to eventually re-seal this shower as it is limestone and will need it eventually and fairly often. I knew this going into the job but the guys who sold the stone said it would do well in a shower as long as I kept up with the sealing on a semi-regular basis. Sooner or later this grout is going to see sealer. I don’t think it is possible to re-seal the tiles without getting any on the grout. If the grout goes bad because of sealer I will just have to remove it and re-do it with normal grout in the future when that time comes.
Dear Elf,
As always, thanks for your helpful advice and sharing your knowledge.
What’s been your experience in using modified vs. unmodified thinset with Kerdi ?
It seems Shluter recommends against using MODIFIED thinset to bond Kerdi membrane to substrates or bonding tile to the Kerdi. The concern seems to be that Kerdi blocks vapor/air diffusion so well it might inhibit the latex curing process. I don’t see any drawbacks of having to use UNMODIFIED thinset to bond Kerdi to the substrate, but it seems many tile manufacturers recommend/require using MODIFIED thjinset for their tile, which conflicts with Shlutrer’s recommendations.
Thanks!
Hi Don,
Sorry, we don’t discuss controversial issues here.
I have used both types of thinset over both kerdi and ditra – haven’t had a problem with either of them. That said, I’m sure you know you’ll void your warranty if you go against what Schluter wants.
Kerdi recommends unmodified both over and under – and there really aren’t problems with that most of the time. HOWEVER! The TCA specifications require modified thinset be used for porcelain – there’s the problem. When it is all said and done I tend to follow the recommendations of the particular tile manufacturer. I know both will work with kerdi and the manufacturers are the ones familiar with their particular tile – I go with them. They’re recommendations, by the way, normally always trump any other standards, as well as the TCA specs. The one place I will not use modified thinset is in a steam shower – latex leaching may be a problem down the road. Other than that I follow the manufacturer’s recommendations.
Hello,
I’m building a new house and want to include a barrier free shower in the basement. I understand using a membrane going up the walls and covering the floor of the shower, but what do I do in the opening? There is no curb to stop the membrane at. There will basically be the same tile on the floor outside the shower as inside it.
I’ve searched the internet but cannot find a description of how to do this.
Thanks
Hi Jerry,
You should have a ‘speed bump’ of sorts at the opening of your shower unless you are waterproofing the entire bathroom. The liner will run up and over the apex of that speed bump and about six inches out under the bathroom floor. With curbless showers you need to either waterproof the entire floor or have some sort of barrier to hold water in the shower with a high point from which the water is directed into the drain.
Roger, this one is driving me crazy. So I have the tub/shower all built and ready to apply tiles. I’ve used cement boards on top of backed insulation (with cuts in the backing) and then 3 coats of redguard on top of the cement boards. So, the whole 3 walls of the tub/shower look pretty darn solid and waterproof. However, on the shower plumbing wall, there are the two pipes that come out of the wall – the small pipe (where the water comes out into the tub) I was able to drill a perfectly placed and sized hole in the cement board and then apply caulk and redguard on top of the caulk and it seems pretty secure. The larger pipe, however, is where the problem is. It’s a Moen fixture which has a large pipe plus a bracket that has two holes that I’m supposed to screw long bolts into once I add the tiles and then add the fixture cap. So, here’s this nice pipe hole with triangle cuts emanating from the center to where the small bolt holes are that I can’t seal up. This all seems to defeat the whole purpose of the wall’s waterproof integrity. When I place the fixture saucer-like cap over the tiles and bolt it into the bracket behind the cement board, I will, of course, caulk around the cap. Is that supposed to do the trick?
Hey Doug,
Yeah, it does for the most part. I like to place a ring of silicone around the outside of the hole for the fixture and leave it a little proud of the wall. Then when you place your tile over it the tile sandwiches the silicone between it and the backer creating a seal for any water running down the wall.
Thanks again Roger! You’re the best.
I have a question about how deep the preslope can be at the drain, Im redoing an old shower and building the pan, I cut my 2″ drain pipe flush with the floor and when I stick on the drain its at about 1.5″ from the basement floor to the bottom of the drain where the presolpe would stop at. Is that OK, since it would be 1.5″ at the drain and 1.75″ at the edges since my shower is only 32×36 and the drain is just off center. Im fine with that just not sure if its ok to have it that deep for the preslope and if that is ok how deep should me second layer over the membrane be?
Thanks
Kris
Hey Kris,
It can be as thick as you want it to be up to about four inches – 1.5″ isn’t a problem at all.
Did you get my question about the shower in the adobe house? If not, I will rewrite it. Thx!
Yup, I got it. But I actually work all day and don’t get to questions until after work. Patience Grasshoppa.
Roger,
Thank you for this site I have learned a lot and I fear I may have learned that my kitchen floor may have been incorrectly installed 6 years ago. I had a contractor remove berber carpet that was in my kitchen (what were they thinking?) before I even moved in the house. He then laid down a green plastic mesh right over the 3/4″ OSB subfloor and then tiled right over that. It is holding up fairly well so far it seems. There is one tile with a crack and no cracks in any of the grout but was this an acceptable installation method?
I called another contractor to tile my tub surround. He was going to put drywall up around the tub and then use the same mesh and tile installation method as above. Drywall in the shower area did not sound right to me so I did not hire him. I asked him why he did not use cement board and he said he did not want carcinoma.
Hi Chris,
Carcinoma, huh? That’s a good one. Let me translate that for you: I’m too frickin’ lazy to cut and carry cement board.
It only causes lung problems if you cut it with power tools and breathe in the dust – no one with any sense does that.
I really have absolutely no idea what type of ‘green mesh’ you may be speaking about. Do you mean a green membrane like ditra? (I’ve never seen one, but I don’t live everywhere) Or do you mean a green mesh similar to what may be used to put up a temporary fence – plastic chicken wire? In that case, no, it isn’t even close to an approved method. It isn’t even close to ones that aren’t approved.
And the ONLY time drywall is used in a shower is behind the Schluter kerdi membrane – that’s it – ever. I guess you get no waterproofing with that method, eh?
Yes, green temporary fence is a good description of what it looks like. It looks like the mesh is called Pro/Float. I don’t believe he intended to include any real waterproofing since he claimed that tile itself was waterproof. Fortunately I convinced my wife not to hire him (she called him to come out and give us a quote as he did tile work for a friend of ours ).
Hey Chris,
Never heard of it. Regardless the shower does need to be waterproofed – but you already knew that.
We had 20X20 inch tile installed in our kitchen, dining area, laundry room and bathroom. We are having problems with cracking grout throughout the area (about 500 sq ft). We haven’t been comfortable with the tile companies response so we hired our own inspector to determine what the problem is and what should be done to fix it. One of the problems he found was that the deflection in the floor is greater than what the 20×20 tiles can support. He explained to us and I have spoken to a couple other tile people that this is something the tile company should have addressed before they sold us and installed the tile. When I shared this with the tile company the owner more less blew this off and his take is that it is not their responisibility and he stated that no one really checks that.
What is your take on this?
There are other issues with this install (lippage, hollow sound on the tiles), but I figured I’d start with just one question
Hey Nate,
It is absolutely the responsibility of either the tile company or, ultimately, the installer. Any type of tile installation needs to be installed over a substrate which will handle the load as well as have the necessary rigidity for the long-term durability. It is their responsibility in most cases, always in remodels unless and architect was hired to spec the installation, in which case the architect needs to ensure the floor has the proper deflection ratio.
They did lay Ditra ontop of the existing floor (wondering if they installed it properly). From what I have researched Ditra is supposed to help with some of the deflection. According to the inspector’s report we hired the tiles we have would require L420. Would the Ditra handle this if it was installed properly.
Also, would the tile company/installer be legally obligated to check that the floor can handle the tile they sell & install for us or is this just a best practice thing any company worth their name should do?
Ditra is NOT approved over a single-layer plywood substrate – it requires a double layer. The fact that they disregarded that very specific requirement makes them responsible regardless of who they think is at fault. A tile floor, REGARDLESS OF THE CURRENT DEFLECTION RATIO always requires a double layer of plywood a minimum of 1 1/8″ thick. That is a very basic requirement for a tile installation and one either the company or the specific installer is required to address.
Unfortunately in most areas there are no ‘rules’ or ‘laws’ requiring adherence to installation requirements. As far as legal obligations your best bet would be to contact Schluter and they can send you the minimum requirements for installation of their product. With that in hand you can show it to the company (or a lawyer) and it will prove that, at the very least, the product was improperly installed and the replacement responsibility falls on either them or the party that improperly installed it.
Every contractor worth their salt checks and fixes these problems. In a sub-contracting environment it is different with different companies. I’ve been out of that scenario for years but it is the responsibility of either the company or installer to ensure the floor will properly support the installation.In the end I’m absolutely certain the company will place it square on the shoulders of the installer, whether they have ever even heard of the requirements or not – just to cover their ass. ‘Well, when we hired him we assumed he knew what he was doing…’ I hear it all the time and it’s bullshit. The installer may or may not know any better (he SHOULD, but he may not) but the company damn well should know better.
Roger,
Someplace above in a post the person is asking about a header in the shower and you reply that the header should be waterproofed. What is a header in a shower. Is it a ceiling? Don’t all showers have ceilings? Does the waterproofing only apply if the ceiling is tiled?
Thanks for helping me understand.
Paul
Hey Paul,
A header is different than the ceiling – yes most showers have a ceiling.
A header is a small ‘wall’ dropped down from the ceiling 12″ – 18″ and blocks off the top of the shower. In other words, vapor and steam that rises cannot escape – the header traps it.
Roger … as my “bathroom remodel project” comes to a near completetion (caulk, trim & sink and toilet reinstallation still needs to be done) I sit here and wonder if I did everyhting right. I allways doubt myself 24 hours after doing something. Did I make the walls flat enough, did I put enough regard on, was the amount of thinset used enough, did I seal the grout correctly etc etc etc. Well as I look back at the last 3 months (yes it has taken me that long) I say job well done Richard. Is it a perfect installation from the outside looking in NO, by any means. Is it better than what was there when I purchased my half acre of hell, YES I say! So to you Roger, I thank you for all the helpful and insightful comments and quick responses. If I can get the courage up to take a few pictures and email them to you I will. I don’t want you to see how rank of an amateur I truly am. But please be gentle with your comments, ahhhhh screw that if you see something in the pictures point them out to me i’m a big boy (have to be i’m a Browns fan). Once again thanks for all the help.
Elf Man (Jedi Master),
I’ve read you don’t need to Kerdi a drywall ceiling. General rule is to Kerdi just pass the shower head. IF I have a header (about 6″)–again drywall on ceiling–would I need to Kerdi it as well due to possible trapped water/steam vapor? I really don’t want to buy more Kerdi and Kerdi Band the transition between wall & ceiling, but I will if you tell me so. I was planning to simply thinset my 12×12 porcelin tiles directly to the drywall ceiling. I’m afraid you gonna tell me to bite the bullet and Kerdi it all due to the header, huh?
Your Padawan Learner….
Sam.
Sorry, you know what I’m gonna say – don’t you?
If you have a header in the shower you need to waterproof the entire interior due to vapor permeating the substrate. Sorry.
Bullets are yummy, Sam – BITE IT!
Thanks for our great site.
I am rebuilding a 50 year old shower on a concrete slab. Have reframed were needed and installed a new P trap. I just finished the Pre- Slope. I am using a PVC liner, Hardibacker walls and Redgard the the Hardibacker.
My question is with the transition of the Hardbacker to the PVC liner, and were to stop the Redgard. I will leave a gap of a 1/4″ between the liner and the bottom od the backer board. Do I silicone that edge and Redgard down to the liner? Then make the mud deck? Or do I put in the deck mud then lap the transition of backer board and mud with mesh tape and Redgard wall and the seam?
I read your Waterproofing guide. You have a gift for clear communication. Thanks.
Hey Paul,
When using a liner with redgard on the walls you want to create your mud bed – both of them – then bring your backer down to within 1/8″ of the top of the mud deck. Then silicone that gap to create a barrier between the backer and mud so the backer does not wick water. When you install your redgard paint it all the way down over that silicone onto about two inches out from the wall on the floor. You will see streaks of the silicone in the cured product where the redgard did not fully adhere to the silicone – that’s fine. All your doing is ensuring that there are no gaps at all in that silicone line which would break your waterproofing sheet – the redgard will fill those gaps as you paint over it. No need for mesh tape at all down there.