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.
Thanks for your great manual! Saving us a small fortune! I have a question about the depth of the deck mud. We are creating a European curbless shower in a new home we are building. We’ve got the drain plumbing up through the floor (cement slab) for the shower drain and the claw foot tub drain. Tub drain is easy and we’ve got Laticrete drain for liquid membrane (hydroban). The entire area under the shower and tub is currently about 5 inches below the level of the rest of the bath. So we will be building that up for a smooth transition and then sloping to shower drain. My questions: Can we fill the deck mud that deep and will it be strong enough to hold a claw foot tub? I’ve seen (including in the Laticrete drain manual) that deck mud should be .75 to 2.5 inches deep. Ours would have to be about 5 inches deep to bring it up level with the rest of the bath. If it can only be 2.5 inches deep what do we do? Two layers (curing the first before laying the second and slurry between)? Would 5 inches be too thick to cure in one pour? Thank you!
Kimberley and Matt
Hi Kimberly,
It can be 5 inches deep. It will support the tub IF you are using 12×12 or larger tile. It needs to be able to dissipate the weight. It may be better to fill with concrete beneath your tub rather than deck mud. It will all cure at the same rate no matter how thick you make it – it cures through hydration (chemical process) rather then evaporation or dry-curing (requiring air).
Hi Roger,
Extending a Schluter base (30×60) to 38×60 over plywood subfloor. Do I need cleavage membrane and / or lath under the added base?
Schluters demo doesn’t show any of this, only wetting the subfloor. I’ve got both roofing felt and lath laying around anyway.
Thanks,
Greg in FC
Hi Greg,
It wouldn’t hurt, but it’s not really necessary. I wouldn’t use the lath, but probably would put some of the roofing felt under there.
Roger, many thanks for your website and insightful instructions. About to tackle my own shower project, mud floor on concrete slab. Many questions, here are a few to start:
1. Using cement backer over the liner, how far up is considered standard height for the water proofing membrane?
2. Putting up a pony wall approx. 40″ tall, between shower and bathroom floor. Wall will tie into the entry curb. Do I treat interior pony wall as shower wall too? Or do I cover all sides with cement backer on membrane? Do I have to consider lathe too? Plan to put glass on top of subject wall too.
3. Considering sloping entire floor 5’x3′, (long ways, left to right), into a 3″x36″ drain, possible tile or grated drain. Idea is for larger tiles or possibly a 1 piece of shower floor, eliminating / minimizing grout maintenance. Need your professional insight on recommendation(s). Quartz, silestone, or other better recommendation for durability and good COF for non slippage?
Yes, I’m stuck in planning mode, while my entire bathroom is partially demo’d.
Hi Roger,
1. It needs to be a minimum of 3″ above the finished height of the curb.
2. Yes, treat is as a shower wall on the inside – that’s what it is. No worries about lath. The top of it should be waterproofed as well, and sloped toward the inside of the shower.
3. I like quartz on shower floors, works well. I would stay away from the polished natural stones like marble or granite.
Thanks for your speedy reply. Clarification re: quartz floor..large tiles OR solid piece? A tile guy stated it was a bad idea for a solid piece referring to degradation of silicon / caulk near the custom drain future maintenance. Would quartz be your only choice? Where would a tumbled or “roughed” corian solid piece be ranked compared to quartz? Have you done any solid floors as I am considering?
I’m referring to large tiles. I have seen solid slab floors, but they’re always something like flamed granite or a ‘tumbled’ marble (not tumbled really, but same rough surface). The degradation of silicone is BS – it would do the exact same thing as it would with smaller tiles. There should be no silicone around the drain anyway. Ever. I have not done any solid slab floors.
I’m a tile novice, redoing my shower completely.
The builder saved some time and energy, by choosing not to use traditional or topical waterproofing. Instead, they chose to use 2 layers of sheetrock and tile directly to that. I have replaced some rotten boards and am going to rebuild it correctly.
There are 2 parts that look different than the examples I’ve found on your fantastic website so far.
The floor was built (seemingly) correctly; Concrete Slab floor with pre-slope build in -> Rubber Membrane- > Deck Mud -> Tile
Then the walls, the studs were framed in solid at the bottom with 2x6s between the studs, and the rubber membrane went up the walls. They then put the sheetrock down to the rubber membrane, and filled in the sides below the sheetrock with lath and mud (of some kind).
One of the walls does not go all the way to the ceiling, so it butts into an external wall that continues through the bathroom (and has an external window – outside of the shower part). This makes a constraint where I don’t want to make the part within the shower, thicker than the sheetrock. ..It used to be, because their tiles ended with an edge piece that rolled over the extra sheetrock.
This is my first question;
For going up the walls, I don’t want to redo the original technique of lath & mud on the bottom, for one reason it will need to be half as thick, as I’m not planning on having 2 layers of sheetrock above it. I was thinking of shimming the wall out above the membrane, then applying traditional waterproofing and wonderboard lite (which seems to be about half the thickness of the sheetrock, So I want to shim it out the other half or 1/4 inch.) My concern, is that in your instructions, you cut 1/8th of an inch out of the bottom studs for the rubber membrane. But shimming the top would leave 1/4 inch gap down on the solid part of the wall between my wonderboard and the membrane not the recommended 1/8th… Should I just leave this (is that 1/8th important), or should I plug some thinset (or something) in there as I set the wonderboard in? (And is my plan OK.)
Next issue is that the entrance has a curb built of 3 2x4s, and the walls go up beside it. The original technique was lath and mud that covered the inside and top, and then a strip of faux marble attached to the top of that. The exterior part of the curb was sheetrocked to match the walls there. If I build the curb out any thicker than the walls next to it, it won’t look right. I don’t want the faux marble strip, I want the inside and top fo the curb tiled. If I tile the outside, I don’t think it will match the walls that it runs into. I’m asking, should I build the curb 1/2 thick, over inside, top and outside, and then on the outside just butt the sheetrock up to it?
(on the inside I assume no issue butting the wonderboard up to it.)
I’d also be happy for other suggestions, if my description even makes sense. I’m budgeting an additional $25 for beer, do you think that’s enough for a novice on a shower project?
Hi Brent,
I’m assuming the wonderboard lite you’re speaking of it 1/2″ thick, yes? Because you can’t use 1/4 thick board on walls, it just doesn’t have the strength needed to prevent flex. You can shim the backer out to go over the liner, that is another method I use. You don’t need to fill that with anything, gravity prevents water from climbing up the membrane.
Yes, you can just butt the drywall up to the outside of the curb as you described. No issue on the inside.
Thanks Roger.
It was not 1/2″ thick, but I’ve replaced it with wonderboard that is.
I feel constrained to use traditional waterproofing, because the concrete on the floor does not have a consistent slope, and it ends with a little bowl shape with the drain in it. It’s really nothing I want to put tile directly on… So a deck mud layer that I can make a nice consistent slope seems necessary.
But I also want a niche, and it looks like the niche instructions work better with surface waterproofing.
So I’m back to deciding my waterproofing method.
1) Are there options for surface waterproofing the floor over top of deck mud? (I assume it’s not good to surface wp the walls, and traditional wp the floor.. it seems bad to me.) ..or is there a better way to reshape the concrete floor I’ve been given?
2) But if I stick with traditional, your niche instructions definitely call for surface waterproofing. How do I transition the surface to traditional there?
I appreciate the help.
I just learned some more stuff.
I found and bought your e-book on installing topical walls with traditional floors. I think that’s what I need to do. Niche instructions will now fit right in, and I’m also going to add a corner bench, (Topical).
So you’ve answered my questions with information that you wrote earlier. Between that e-book, and your niche and bench instructions I am finally ready to start. My wife will be happy to hear it.
Thank you floor elf.
Oh, perfect. Thanks.
If you need anything else just let me know.
Yes, you can use a topical waterproofing like kerdi or hydroban, redgard, etc. on the floor as well.
You silicone the face of the waterproofing membrane (behind the backer) to the back of the backer around your niche, then use topical waterproofing in your niche.
Hi Roger,
I’m not sure if this would be a question for you, but here goes. I recently had someone come in to repair the shower drain pipe located in the space under the shower between the second floor and first floor ceiling. When the project was completed and the ceiling drywall was replaced, we noticed that there was a slight bulge in the ceiling from what looks like the shower drain pipe being too long. What is the correct fix for this? Should I have him come back and shorten the drain pipe? Should there be some clearance between the pipe and the drywall? Or, should we just sand down the drywall to make it flush with the rest of the ceiling, thereby making the ceiling about 1/8 inch thinner?
Thanks in advance for your advice
Hi Al,
The p-trap is too large for the space. Being only 1/8″, however, you can either have him come back and fix it, which would require removing, redoing that portion, or you can sand down the drywall as well. If it isn’t yet taped and mudded you can also remove the drywall and cut the 1/8″ out of the back of it for the bottom of the p-trap to sit into, so the drywall doesn’t bulge.
Hi Roger,
Very frustrated as I am about to remove all my floor grout due to efflorescence. My tiles are 1’x2′ so there isn’t that many grout lines to deal with, BUT nobody wants to end up here. The grout is a dark brown (Polyblend) but the whitish efflorescence is totally uniform and goes all the way down to my thinset! No product or method could remove it. Guess the tile hadn’t cured (2 days) and I used too much water in mix and cleanup. I suppose that since I used Schluter Ditra that moisture could only come up through the joints. Now my question. I have been instructed by a local pro to use an acrylic additive. I didn’t get to follow up so I am wondering; can i use an acrylic additive with the Polyblend grout? Can I still clean up and do haze removal with sponge and water? Are there any other differences or tips to using an acrylic additive and/or prevention tips that you can share (links are great too). Thanks -Ben
Hi Ben,
Polyblend is one of the worst grouts I’ve ever used. It effloresces a lot. In my experience acrylic additives can create more problems than they solve. If you can’t switch to a different brand of grout then I would (literally) weigh and measure the grout and water.
Roger
Love your site not sure I would have been able to get this far on my shower without it. I have a couple of concerns/questions. First i am building a traditional mud pan shower floor everything seems to be going great following your instructions page by page. However the pan and curb is done and i notice that around the edge of the pan if I tape on it,it kind of sounds hollow is this normal?
Second question we have picked out this mosaic tile for the floor that is one inch squares and when I run my hand over it it seems to have real sharp edges and I am concerned about this, will this be an issue or is it normal or do people complain about the sharp edges?
Thanks
Hi Dale,
Yes, the tapping along the edges is normal, you have a thicker bed of mud on the perimeter. If they feel sharp to your hand they will feel sharp on your feet. You may want to pick a different tile for the floor. If it’s for the walls it will likely be just fine.
If I order one of your books today, when can I expect to receive it? I cannot find shipping information on your site?? Thanks….
Hi Curt,
About two minutes after you pay for it. They are all electronic files – ebooks. Not physical manuals. Once you make payment you recieve a link to immediately download it.
I have vinly tiles in my bathroom and they contain asbestos.
So I’m really scared to remove them due to the obvious health issues.
1. Could I put cement board over it and then tile on the cement board?
2. Is there a particular type of thinset you recommend to use under the cement board?
Certified asbestors removers are expensive as hell
Hi Rajith,
If you have a wooden substrate beneath those tiles then yes, you can put cement board over them and tile over it. Any thinset will work beneath cement board, it is only there to fill voids, not to bond.
If you have concrete beneath those tiles you need to use something like greenskin membrane over it (google it) or use a primer and a membrane which installs with thinset, like ditra.
I’ve got a 1/4 ply under the vinly and 1/2 ply under that. So I guess I can go ahead with cement board. Thank you!
More questions
1. Is it OK to use the Shulter Kerdi Shower Niche with 1/2 dense sheild board. I plan to use the Kerdi band to tape the seams. Is it fine?
2. Is it ok to use the Kerdi band to seal the Dense sheild board joints? Or is this overkill? Can I just use fireberglass tape + thinset here and above?
3. I plant to do a shower stall in my basement later. Is the Kerdi shower base worth the money? I hate the cheap plastic pans and would love to have tile on the bottom.
Btw your books are amazing, I got the confidence to do this myself after reading them. Thank you.
Rajith
1. Yes
2. Yes, not overkill, the seams need to be sealed anyway.
3. Yes, they work very well, although I prefer a mud pan.
A) I started on the living room floor first. I put down the cement board.
For the first batch my thinset was a bit too thin, then over compensated in the next batch :D.
B) I put down too much thinset , then realized it and reduced it a bit, perhaps too much, before finally hitting a sweet spot (or so I think).
C) I want to wait a bit to see if there are any issues with my cement board installation before putting on the tiles. I’m especially worried about less coverage then anything else.
1) If there are serious issues what are the symptoms ?
2) How long do these issues take before they start to show up? or are these only visible when u put down tiles and they start to crack?
I’m a bit worried
1. You will notice the backer move when you step on it if you don’t have full support.
2. You can see this after 24 hours (after the thinset cures). If it doesn’t move you’re fine.
Thanks for the reply Roger.
Btw the floor creaks in a certain section. I don’t see the backerboard moving independently from the floor below. It’s more like the whole subfloor goes down a bit. I wouldn’t say bouncy for sure, but it could be that…. Is this called deflection?
Is there anything I could do? I still haven’t put down a single tile yet.
That is deflection. Nothing you can really do from the top of the floor. If you can get beneath it you can shore that area up, but from the top you’ve done as much as you can.
Thank you. I’m going to try to shore it up as much as I can.
Thank you again!
Hi Roger
I think your website is really good, but I’m struggling to reconcile myself with the idea that tiles are categorically not waterproof. If so, how come my roof doesn’t leak? And come to that, items of porcelain crockery such as the bowl I eat my breakfast cereal from, etc., are clearly waterproof – and I’m pretty sure the white porcelain tiles in my shower are made from effectively the same materials. If not, why not?
I’ve spoken with a couple of friendly tile experts for advice on why it might be that my shower is leaking, and I’ve mentioned your comments about tiles being non-waterproof, but over this side of the Atlantic (I live in England) the consensus (as far as I can make out) seems to be that yes, they are, to all intents and purposes. I realise that even a “waterproof” coat for example, or an “impermeable” stratum of rock in geology, will let water through to some degree but you yourself give figures as low as 0.005% (I think that was the figure?) for how much water by weight some varieties of tile will absorb if completely immersed. Surely, in a shower where the water is able to run straight off the surface, that is sufficiently low to mean the tile is effectively waterproof?
I’ve had a look underneath the shower tray and it’s clear from what I can see of the stud work behind the tile surround that one side has had a lot of leakage, while the other side looks dry. It’s a corner shower so only two sides are tiles. Inspection of the tiled surfaces inside the shower reveals hairline cracks in the grout on the leaky surface, or that’s how it looks to me anyway, & the advice I’ve been given is to regrout and make a careful check of all the silicone, and replace that too if in doubt. However I do not believe any kind of waterproof substrate was included in the original installation so do you think I am wasting my time if I don’t go back to the stud work and start again?
Look forward to hearing back from you…in the meantime, have a great Christmas!
Best wishes,
Ben
Hi Ben,
Your roof doesn’t leak because the substrate beneath your roofing tiles was properly prepared with a waterproof sheathing, tar paper, or the like. It doesn’t need to be a lot of water, the problem is that it will build up. If your cereal bowl had a gash in it which you filled with a cementitious filler and left milk in it for ten minutes every day without wiping off the counter beneath it, you would have a large puddle of milk beneath it within a couple of weeks.
If your shower is leaking it is due to a problem with the substrate not being properly waterproofed. There is nothing you can do over the surface of a tile installation which will permanently stop the leak. You may be able to slow it for a period of time, but it will NEVER be permanently fixed. Your waterproofing is a construct of your substrate. If it is not waterproof your shower is not (and never will be) waterproof. If you do not take it down to the studs and rebuild it properly you will never have a waterproof shower.
I installed 1/2″ hardibacker on 16″ center studs above a shower pan. Then I Redgarded the walls and installed 12 X 12 ceramic tiles with Acrylpro. From checking some info on the internet, this looks like a wrong method. I wasn’t sure from reading your info if I made a mistake or not. Please advise.
Hi Scott,
Actylpro will NEVER fully cure over redgard beneath tile. It needs to be installed with powdered thinset you mix with water. On the upside, it’ll be fairly easy to get the tile off the wall.
Sorry, I know that isn’t what you wanted to hear.
I am wondering how to tile a drywall/tile outside corner?
Do you butt the backer board to the drywall, or vice versa?
Do I use a corner bead, or just a tape corner?
I couldn’t find anything on the website, and I am gonna flip through your tiling tips and tricks ebook for an answer.
Thanks
Hi Brendan,
I normally use a plastic corner bead there. You can just tape and mud it, that’s works as well, but the plastic corner beads work very well. Do not use a metal one, it will rust beneath your tile.
Won’t the tape and mud crumble on the tiled side of the wall? I was thinking of overlapping,the backerboard by 1/2″ and then butting the drywall too the backerboard.
I’m not sure how tile will hold up being set on a corner bead and drywall mud ?
When I say tape and mud on a tiled side of a wall what I mean is alkali-resistant mesh tape and thinset as mud. You can do that on both sides, thinset can be sanded and painted like drywall mud.
Hi Roger,
I love this site and your witty personality. It suits my personality perfectly. Right now I am having my bathroom remodeled by a floor guy. My shower was disgusting with mildew everywhere. I REALLY want the shower to be right.
There was backerboard everywhere, NOPE, not the green treated sheet rock. Sheetrock is on walls in shower and tub area, new backerboard is laid on the shower floor and now the guys simply wants to add the concrete. I’m like NOOOOO, something isn’t right. Don’t know what.
I did read above but couldn’t understand the part about seal this but don’t do that and add this but not that because I’ll get the mold sandwich. (P.S. There was mold on wood and just a tad on the flooring and insulation. NOT MUCH though, SURPRISINGLY. He treated wood with concentrated clorox and changed 2 pieces that were in really bad shape).
So what goes down now? The backerboard is down. What next? Please help me as I work to act like I know what I am saying.
P.S. My shower is about 116 square feet, I’m thinking 1 bag of concrete vs 4 bags is plenty.
NEED A RESPONSE ASAP (caps are not yelling)
ALI B -Atlanta, GA
Hi Ali,
I’m honestly not sure what you have going on there. Backerboard does not need to be under the shower floor, but it can be. The floor needs to be built with deck mud, not concrete. I have no idea what “1 bag of concrete vs. 4 bags is plenty” means??? This will explain a shower floor, but I don’t know what type of waterproofing you are using so I really can’t answer specifics until I get more details on products being used.
I am replacing the kitchen floor (12′ x 12′) in a hundred year old house, the previous kitchen at some time had some major water damage, the tongue and groove wood floor was totally deteriorated in some areas and but about half of the kitchen doesn’t have perceptible damage. It had linoleum on fiber board, on the oak tongue and groove, on 1×6 diagonal rough planks (with 1/4″ spaces between them) on 2×10 joists. I would like to put on 18″x18″ porcelain tile. Since it is the kitchen and since it had previous water damage I am wondering if I need to put in a vapor barrier, and how I should redo the sub-floor so I have enough support for the tile.
I know there are numerous products out there, but I am more curious about recommendations of the process vs. products. Like should I remove to the studs, put on osb, vapor barrier, backer board, thin crete, then tile or is there a better way to do it?
Thanks
Hi Pat,
You do not need a vapor barrier unless you have a crawl space beneath your kitchen. If you do just place the barrier over the joists. I would remove the floor completely to the joists then use two layers totaling a 1 1/8″ minimum, the thinset and backerboard over that. Your tile can be bonded directly to the backer.
I first want to thank you for your very informative waterproofing guide. In trying to prepare for our first diy tile job, we have run into a lot of conflicting information. Our home is over 100 years old and the shower we plan to tile has two exterior walls that are covered in tongue and groove hardwood. The traditional waterproofing method is appealing because it is cheap and easy. But we do have the time, money, and skill to use a topical liquid waterproofing. Considering the two exterior walls, is one method better than the other? Are there other factors we need to consider when it comes to choosing a method? Thank you for your time and wisdom!
Hi Sarah,
Of the two I would use a topical liquid. Having the waterproofing directly beneath your tile allows the shower to dry out completely between showers, it’s a cleaner environment. With the traditional method your backer will be saturated and flush through with each shower. That is completely normal, but the liquid is simply a better system.
Hi Roger, I’d like to get your manual on the kerdi system for shower floors and am wondering if it will cover my situation: This is a re-tile of a shower which was originally tiled with a mortar bed and a thick black poly applied on top of that (unfortunately, my helper cut it out during the demo) and then another mortar bed after that which raised the level of bed to top of drain which the tile was set on. I think the drain is two pieces and I can take it apart and put a new water barrier down. I’ve read that there is a special kerdi drain for this type of application. I was hoping your manual would give me instructions on this. Would it?
BTW: it’s a cement slab so no access to drain below. thanks, douglas
Hi Douglas,
No, the manual does not cover the kerdi clamping drain adapter. It’s fairly straightforward, though. You just bolt the clamping adapter down onto the bottom of your two piece drain, the the drain secures into it. This is the product you are looking for: Kerdi clamping drain adapter
Hi Roger,
Any problem with using AquaDefense or Redguard above Kerdi membrane on a very tall shower stall? Would like to save a little moolah!
I would like to stop the Kerdi above the shower heads, and waterproof from the top of the Kerdi upwards to the ceiling.
Thanks,
Greg in Fort Collins
Hey Greg,
No problem at all.
Hello
I never tiled a shower stall.
I have been told to keep the tile gaps very small which MAY help with seepage. The stall in our upstairs has no real gap and seems to be working well for 15 years. What’s your view on the proper gap???
Thanks
Hi Sandy,
Proper gap on what? Any ‘seepage’ is controlled through the proper waterproofing of your shower substrate, it has nothing to do with a proper gap in anything. You may want to begin by reading my waterproofing manual. It will answer a lot of questions for you.
I have very bad mold issue at my new boyfriends house. I mean a VERY BAD mold issue!! I can send you pictures of you send your email. I need your simple explanation if it can be repaired or if the tile needs to be completely replaced.
If you have time to respond.
I would really appreciate your help :-)
Thanks,
Sone
Hi Sone,
I can look if you upload the photos here: Photo upload If you have any information about the substrate or how the shower was built that would also help tremendously.
Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.
Roger:
Hope you are doing well. Thanks for all of the help.
As you suggested, I left a small gap (probably 3/16″) between my tile and the shower base, to allow for any moisture that gets through tile/mortar to have a place to drain down to the pan. Used HardiBacker and Red Guard under tile. Anyway, with this small gap, water inevitably gets into or rests in the crack and now mold and milder grows between the pan and bottom of tile and is starting to creep up the tile too. I dry the shower well each time, but need to clean out this mold growth every 1-2 months.
Do you still recommend against filling this gap with silicone? My thought is that if you did everything right, does that much water get behind tile the tile and mortar that it would need to “drain” out/down to pan? If showers are kept to 10-20 minutes, it is not standing water against tile, the shower walls are squeegeed each time, and tile is sealed (I know this is not a moisture barrier), etc. I wouldn’t think much water is truly getting to RedGuard in the amount that it would need to drain down wall.
Thoughts?
Thanks for the help.
Devin
Hey Devin,
The problem may be wicking moisture through the hardi. Go ahead and silicone it, as long as the water can still drain down the face of the redgard and into the pan you’re fine. And yes, enough water will get behind there that needs to drain.
Roger:
Thanks for quick reply. I am not trying to be “smart”, I just want to be sure I understand this. How can I fill that gap with silicone (from the outside) while also allowing water to drain through it (from the inside)? Filling it with silicone will prevent water from splashing into the crack/gap and mold/mildew growing, but then the gap will be filled with silicone, so no water from behind it would be able to drain out into the pan…right?
Please let me know your thoughts. If pictures would help, please let me know. Thank you so much.
Devin
You stated you have a 3/16″ gap. That is enough to get the nozzle of the silicone in there to silicone between the base. After that cures you silicone between the tile and tub leaving weep holes for water to drain.
I followed your directions on installed porcelain no hard floors (completely remove hardwoods and install hardeboard in its place. Now after just over a year the tile makes a popping and cracking sound but it doesn’t actually crack. what did I do wrong and what’s the remedy? PLEASE HELP ME!!!!
Hi Anthony,
Did you put thinset beneath your tile? What size trowel did you use? What thinset did you use? Did you backbutter the tile?
Roger,
Do you recommend any sort of tile leveling system? Or is it just not worth the money? I saw this on youtube http://bit.ly/1wwLaAL
Thought I’d sort your opinion before I spend the money.
Also I’m using dense sheild for the shower walls. The info sheet says to butt the panels and then use fiber glass tape for the seams.
Do I use thinset to mud the seams ?
Should I still use water proof membrane over the seams?
Your answers are greatly appreciated.
Rajith
That video is almost identical to the raimondi system, which works very well. I use the mlt system. It is a method of holding the tiles in place while the thinset cures so the tiles don’t move if the thinset shrinks. They work well, and are well worth it on large format tiles.
You want to use a sealant like kerdi-fix or sika flex between the sheets to waterproof the seams, then use alkali-resistant mesh tape and thinset over them to tie the boards together. If you properly seal it you don’t need a membrane over the seams.
Thank you very much!
Rajith
Thank you Sir! :BEER: ….err, :hot chocolate:
One last quick question(for now), what should I use to bring the height down now that it has been two days?
Thanks!
You can scrape it down with a chisel or sand it with a brick.
Ok, one more….
I scraped down the showerpan and I had some gaps, which I filled when I did the thinset slurry(thicker in places). Now when checking the floor there are still some gaps where the floor is not smooth. In a couple of places there is an 1/8th in gap.
Do I have to fill that before I redguard?
The last thing I want is to blow this and have to start over.
Feeling
Thank you!
Yes, you have to fill those. You are working on the actual substrate for your tile, the redgard just waterproofs it. The flatter you get it the better your final installation will be.
Roger,
I got a little over zealous with my cement grinder
, and now have some dips. Can I fill them in with thinset to even it out?
Thanks!
Hi Rees,
Normally yes, unless they are huge, like larger than 1/4″ from plane.
Cement grinders are fun, huh?
Somehow I missed your reply.
Thanks! Nothing larger than 1/4.
Cement Grinders are a blast? LOL.
HELP! We used Kerdi board on an exterior concrete block wall in the basement bathroom because it could be applied directly to the concrete block. If we’d built a stud wall and used drywall over the studs, we would not have had enough (code) clearance for the toilet. We have tile wainscoting on that wall and so I wrote to Kerdi to ask how to prepare the exposed Kerdi board for painting, i.e., skim coat? or what? And they said that Kerdi is meant only for tile, not for painting.
WTF do I do now? HELP! We don’t want tile to the ceiling and even if we did, we have no more tile and this particular color is discontinued.
Hi 732,
Skim-coat it with drywall mud, let it cure, then paint it. They don’t want your liability.
Roger,
I have built my mud deck, but I’m a little concerned….
We went with 3/4 inch even though we’re at 33 inches from the drain to furthest corner. Seemed like the right thing to do.
The perimeter height is all the same as required.
The drain is no centered in the shower and the rise on the side is 3/4 inch in 7 inches. It seems to me that this is sloped rather steep and a recipe for many slip and falls.
Thoughts?
Hi Rees,
Completely normal if you want a level perimeter. Normally any area small enough to be that steep is one you in which your foot will not fit between the drain and wall. Hard to slip in that scenario.
Roger,
The Space is 7 inches wide, and exactly where you would want to put your foot. CA state code says no more that 1/2″\foot This is more like 1″.
I guess my options are, no level perimeter, or pull it out and move the drain to one end? This is me right about now ->
HA!
Or you can just slope that wall down to 1/2/foot right at the drain so that’s the only wall that won’t be level.
Would going down to 1/4-ish be too much? The wife is rather concerned.
Previously, there was little to no slope, not that it is relevant….
Looking for this shower to be
Thanks
Nope, that will work just fine. As long as you have 3/16″ or more you’re fine.