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, I hope you haven’t addressed this before and I’m asking a repeat question. Thanks to the wonderful people working at and writing books for a certain big box store I’ve repeatedly had to stop what I’m doing and look up your ways to do my tile shower. So I just quit reading and asking those people questions. I’m at the point of tile for the walls. And have set my mid wall point for the tiles. Do I use a batten board to start? Seems like it would be a good idea for straightness and maintaing the tiles. If so do I just run a couple drywall screws through the batten into the Hardie, and studs, then pull the boards and thinset the screw holes? I hate the color orange now for some reason.
Hi Garth,
Yes, a ledger board, or batten, works well to begin the walls. Once you pull the screws back out I would fill the holes with silicone.
Roger,
I’m installing a curbless shower, SOG foundation, sunken slab for mud deck area, Hardi on the walls & embedded an inch into the mud deck, Kerdi membrane on the floor & up the walls & 12″ out onto the bathroom floor, and tile or stone on the shower walls—–
1) At the transition from shower floor to bathroom floor & the 12″ beyond:
a) Should I run Kerdi membrane up the room wall a few inches?
b) Should the drywall for this 12″ section (I’m using Hardi) be treated similar to a shower floor? i.e. 1/8 off the floor, silicone, then Kerdi up a few inches—– as opposed to a typical 1/2″ drywall gap above the floor?
2) I have a shower wall that requires 1 1/4″ shims across the whole wall. I’m planning on using two stacked 5/8 strips of plywood for shims. When I attach the Hardi, should I use extra long screws to insure that the Hardi is attached to the studs, and not just to the plywood strips?
3) Because of the thick shimming in 2) above, the stud on the adjacent wall will be covered/hidden by the shimmed-out wall. I can’t add a stud there due to piping interference. I can put the Hardi on the second wall first (prior to the shimmed-out wall), but:
a) The tile or stone in that corner will not have a stud backing. The Hardi will, but the tile won’t (because the adjacent wall is pushed out past the stud). Is that OK?
b) Simply put, does the tile or stone need to have a stud backing in corners or just the Hardi?
Hi John,
1a. Yes. 1b. Yes
2. Yes
3a. Yes, that’s fine. 3b. The hardi is fine.
Hi Roger,
We have moved into a new house and the shower developed a leak!
Our shower has a fiberglass pan where you walk, and a tile seat along the back edge (across from shower head). The source of the leak seems to be caulk failure (or failure to caulk) under the lip of the shower seat. My assumption is that there should also be a waterproofing material under the seat and behind the tile on the front face of the seat that would have prevented the ceiling damage to the floor below. Is that a correct assumption? Does my question make sense? Thank you!
Hi Ryab,
It makes complete sense. Your bench should be completely waterproofed beneath the tile on both planes – caulk has nothing to do with it. It should be removed and rebuilt/waterproofed properly.
1) Is it reasonable to build a shower with a Kerdi membrane (and tiled) floor, but with cultured marble walls?
2) I assume you wouldn’t want the Kerdi to go all the way up the walls because of mold-sandwich problems. So, how far up the wall would you go past the floor tile? A foot, or maybe less? It’s still a mold sandwich (just shorter), so is that a problem?
3) I assume you would have to seal the bottom of the CM somehow–right? ——a) Would you just silicone the bottom of the CM to the tile and call it done? Probably not.
——b) Or would you silicone the back of the CM to the Kerdi at or near the bottom of the CM as you were installing the CM sheet on the wall?
Hi John,
1. It’s fine to do that – reasonable is relative.
2. A minimum of three inches above the finished height of the curb.
3. I would place a bead of silicone where the back edge at the bottom of the cm meets the kerdi.
Roger-
First, thank you for taking the time to share your knowledge. Unfortunately, I did not read this blog before making my shower pan. Situation: I made an initial preslope with sanded topping. I placed a liner on top of the 1st layer of the sloped sanded topping. I interfaced the liner with the lower part of the drain assembly as oatey instructs. I installed the cement board on the walls and over the curb. I installed the second part of the drain and set it at a height to be flush with the tile after install. I then completed a second sanded topping layer. I then did a skim coat of thin set from a powder mix of versabond in order to address the imperfections (pits/gooves) I created with the second layer of sanded topping that was above the liner. Okay. I then learned about redguard, so I did the inconceivable and coated everything from the shower pan, over the curb, up the walls. The perfect mold sandwhich for my shower pan. :(. So, the situation is since it is redgaurded to the drain, the drain sits 3/16″ higher than the redguarded slope. Which will leave a nice 6″ radius of water with no where to go after the tile is installed. So, I was wondering if it made since to remove the red guard from around the perimeter of the drain…maybe 2″-3″…This would allow the water to seep through the second layer of sanded topping onto the liner, which is correctly interfaced with the lower section of the drain, thus allowing the water to drain out….does this make since or do I need to completely gut my shower pan….and I reallllllllly do not want to do that…..sorry for the long question. Coating Happy Brad…..
Hi Brad,
No need to panic.
You can scrape off the redgard about six inches around the pan and you should be fine. You need the redgard over the curb anyway, I’m assuming you put holes through the liner when you put the backer over the curb. 
Thank you… http://floorelf.com/wp-includes/images/smilies/icon_biggrin.gif
Hi, Roger,
My bathroom shower contractor didnt use any waterproofing membrane behind the substrate – he claimed that in the basement it is not neccessary. I also noticed the lower screws on the bakerboards to be very low from the floor, in my mind also going against the waterproofing logic. Could you, please, share your opinion regarding this? Basically – whether basement bathroon needs to be waterproofed or not. Thanks much
Hi Boris,
Every bathroom needs to be properly waterproofed. Are you in Florida or Texas?
Hi Roger,
Almost done…thanks for your help. Alcove tile shower with 10×20 porcelain tile. The short walls were brought in 1/2″ relative (1/2″ return that dies into bathroom wall) to the bathroom walls to accommodate proper framing requirements.
Original plan was to use bullnose on the return, but my the field tile isn’t plumb towards the bottom because of waterproofing and my poor installation. Do you have any ideas for an alternative to the bullnose? Only ideas I have are to scribe wood moulding or granite.
Thanks in advance. – Matt
I should add that the curb is granite.
Hi Matt,
Look at the different schluter edges available. They can usually fix problems like that.
we had a leak along a grout line in an old shower. We took out the tiles and notice there is a grove in the backer board at the bottom where the tiles were. We let it all dry for about 2 week. Now we wonder how to replace the tiles. Do we fill in the groove in the backer board and with what before using thinset to replace the new tiles ? Then grout and caulk around the rim of the shower. Thanks for any info…
Hi Ginger,
Grout lines do not leak, substrates leak. If you had a leak in your shower it had nothing to do with the grout line. I don’t know what you mean by a ‘groove’ in the backer. That could be the source of your leak, but I’d need to know what it is before I can help you proceed.
Dear Tile God: I “F” up the shower floor when I put the tile in. It wasnt level so I have a 1/4 ” gap in the center where the floor tile meets the wall tiles. I have enough 2×2 tiles to lay a new floor over the old one, but need to ask you first if that is acceptable to do ? I “think” it will work ???? was able to remove the adjustable Kerdi drain and can re install at the proper height to the new floor height. (Using Ditra Set) Everything else, the shower walls, tub surround, bathroom floor came out “perfect”, I mean perfect thanks to you and your manual…… just screwed up on the shower floor. Can you let me me know “before” the dog and the wife go up in flames……….Thanks
Chuck
Hi Chuck,
Provided you can get the drain where you need it – yes you can. No problems with that at all.
OH dear tile God:
Just thinking about the drain when reading other posts………Kerdi drains, do you actually “glue” them in or just press together, it is actually friction based, meaning it is Pressed together and stays tight without glue but was wondering if you glue the drain at the final height ?
Thanks again partner
Hi Chuck,
You install the top of the drain into the flange portion with thinset as you set the tile. That way you can adjust it to the proper height and, once cured, it’s all bonded together with the thinset.
Mr Roger Elf-sir,
Your website has significantly helped me find answers to my concerns when it comes to working on our bathroom shower, out first major project. So thank you so much for everything thus far!
My question is regarding caulk. We used a fiberglass shower pan, wonderboard walls( and liquid waterproofing membrane over the cement board), tile has been installed and grout is sealed. I have waterproof wall paneling I hope to install above the tile in the shower (about 5 inches above the shower head). That area of the wonderboard hasn’t been waterproofed so the glue behind the waterproof panel can cure properly.
Most places I’ve read suggest using 100% silicon ii caulk for the shower. The only colors Ive seen are clear, white, or almond for shower and kitchen applications. Our tile and grout are grey, and there’s a 100% silicon ii caulk for windows and doors that is grey and I would rather use that. They don’t seem very different except when it comes to the amount of mildewcide. The window/door silicone has a bit of milder resistance, but is it enough to be useable in a shower? The store clerk said it would be fine, and a few posts I’ve read online have the green light, but I wanted to ask what you think?
I plan to use clear bath silicone for the waterproof paneling and its molding above the shower, tho. I just don’t want to make a “mold sandwich” or encourage any mildew by using a caulk that isn’t specifically formulated to be laced with poison against it
Hi Kristin,
Silicone is silicone. It’s all completely fine for a shower installation.
Hi Roger
I am installing kerdi board above our shower surround to waterproof it. Is it possible to paint over kerd-board rather than tile it? Thank you!
Hi Jenn,
If you prime it first yes, you can paint it.
Roger,
bought the book – still no word on the movie?
as I am sure remember I am going traditional floor/topic walls.
1)So if HardieBacker were Ginger and Durock were Mary Ann are you a Ginger or Mary Ann guy?
2)Preslope question- in the book you state there must be a minimum of 1.5 inches thick(inc liner &top mudbed)- you suggest 3/4 preslope @drain. My drain is on the slab (slab on grade floor) and the lower drain sticks up maybe 1/8 inch- a few pages later you state a “secret” it will really only be a bit less than 3/4 inch thick @drain – to keep liner from “diving”— so I have to compromise either A) thickness at the drain or some dive in the liner. Is the preslope thickness as important with slab on grade? please deconfuse me— what shall I do what shall I do? Bye the bye my cormer is 4’1″ from center of drain…
3) Liner question- I have 53″ X 78″- ish floor ( with neo-angle door opening) thus I think I must seam my pvc liner – any tips? – I am wondering if I should go three pieces to lay the center flat (on slope) and two ends on top sort of shingle like – or it better to just have one seam and not worry about where the seam lands???
Hi Matt,
1. Ginger, definitely Ginger. MaryAnn is a messy ****.
2. Preslope thickness is not the imperative part – the total thickness is. If your preslope is 1/8″ or so just make your top deck 1 3/8″ or more at the drain.
3. Overlap a minimum 2″ and use the correct adhesive. When seaming liners I always prefer the shingle method. One seam is always best, doesn’t matter where it lands.
Thanks,
I am going to go with Ginger!
I am ready to build my curb- as I am slab on grade – I should use grey concrete bricks and use thin set to adhere them.
I am wondering – is there any reason not to slap in some forms and just pour a concert curb? –It seems like it may take less time then laying brick and covering with deck mud to get the curb to its pre liners/lath shape.
However – If I go this route I am a bit concerned with adhesion between the poured curb and the existing slab.
I seek your guidance and request advice on concrete product types if this is an acceptable building practice.
bye the bye
I bought the “landscape” concrete type bricks @ big box 4″X6″ grey,no holes and regular thin set to bond ( in case you nix the pour idea)
A formed curb will crack. If tile is on the formed curb it will crack too. Yes, just use the concrete bricks. Why try to do everything the hard way?
Vexing issue for me. We had our shower tile redone about 10 years ago because the original tile was in such bad shape. When the contractor pulled up the old tile, the mortar bed was wet which was no surprise since the old tile had areas with deteriorated grout.
He let it dry till it was bone dry, applied 2″ x 2″ tiles and it was great.
Well the other day I was lifting the shower mat and one tile came up completely. so I began to check the other tiles and three more in that same line came up quite easily.
Under the initial tile that came up you could see the actual mortar bed and it had a small divot in it, the other areas had the backing membrane and you could see the tile adhesive (white) so not down to the mortar.
So I put a fan directly onto these areas, running 24 hours, pointed right at them for about 4 days, thinking that somehow we had a grout leak around these tiles. Anyway, fast forward 5 days and the area of mortar beneath the original tile that had come up is still moist to the touch, not drying at all, and the shower has not been used in over a week.
I have no idea what this could be and how to even begin to address it.
Any thoughts and advice is appreciated. Thank you.
John
Hi John,
First of all, cracked or missing grout has ABSOLUTELY NOTHING to do with the mortar under your tile being wet. What did he use to install the new 2×2’s? Was it a white powder that you mix with water, or was it a white adhesive out of a bucket. Because if it’s the latter – that’s your problem. It’s mastic, and it does not belong in a shower floor.
I understand the need to leave a small expansion gap (then silicone the gap) between tiles in corners in showers . However, applying that thought to short backsplashes (say 6″ to 24″ tall) on tub decks (no shower) or sink vanities leads me to ask if the gap is required there.
In short, can I sit a backsplash (stone or tile) directly to a granite top with no gap? It seems that any expansion could move to the top side since the backsplash isn’t restricted in upward movement, and the height of the backsplash is relatively small.
Hi John,
You still need it. Movement isn’t restricted to expansion pushing the backsplash up, if the weight of the granite settles the cabinet a bit it will pull the granite down away from the tile and you’ll end up with a gap there anyway. Same thing applies to a tub deck, filling a tub with water will force the horizontal tile down away from the wall tile. I normally leave about 1/16″.
Hello i have a question, in a long run whats better tiles or shower base for my shower in terms of mold growth.
Thanks
Hi Ka,
Built correctly they are identical in that regard. However, you’ll always be able to clean the tile, once the acrylic is stained you can hardly ever get it white again.
I’m have a pro, doing a total demo & restoration of my bathrm . The shower/tub area is 60X32 alcove tub with a lip[ wall on 3 sides] First Ques. He is putting up cement board. Should he waterproof this with with 2 coats of say, Laticrete Water Tight ? I will also be tiling the bathrm walls coming away from the tub. Is it better to use, say, 1/2 inch cement board there also & should I waterproof those walls & floor with same sealer[laticrete] ? The contractor comes highly recommended , I just want to make sure I get what I pay for . The bathrm is 5’X11.6′ & the price is not the cheap end, Everything going in is high quality ,porcelain tiles -tube – tiolet1pc. Your advice of what to look for would be appreciate.
Hi Ed,
Your shower needs to be waterproofed in some manner, the water tight is only one option. If you download my shower waterproofing manual it will explain the different options. Outside the shower tile can just go right to the drywall, it doesn’t need to have the membrane applied in dry areas.
Roger is it necessary to run a test on the shower pan to check for leaks.
If so can you plug the drain by removing the clamping ring and putting in one of the otey plugs (red with a screw on top to tighten them) down the 2″section of drain , secure the clamping ring again and fill the pan. the reason for removing the clamping ring is I can’t get the plug installed without doing that as I need the extra room.
Any other tips? I would like to avoid the cost of the balloon.
Hi John,
Yes, it is necessary. And yes, you can remove it and use that plug in that manner.
How about this one. I was installing tile on the ceiling with thinset coated the ceiling first than a nice coat of the tile I was about on my 6 th one I pushed it up and just hit it with my fist and exactly what I was afraid of happened the tile before it fell down onto the pan. Fuck me left a small hole from the corner. What the fuck can I do
Hi James,
I don’t know what your waterproofing is on your shower floor. If it’s a topical liquid you can just paint more, if it’s a sheet like kerdi you can use kerdi-fix or put a patch over it. If it’s something else you need to let me know what that is.
Hi Roger,
Thank you very much for your wonderful website. I have been absorbing all the excellent info there like a sponge. I am an avid DIYer but far from a tiling expert as my following questions will show. I am redoing my shower stall and have some questions on tiling aesthetics. The shower will have a fiberglass shower pan (34×48) and a sliding glass door (70″ hi). The tile (12×12) will go to the ceiling, plus the ceiling, and have a 3″ bullnose all around starting at the outside edge of the shower pan. I plan on centering my tile design on all walls but am having a difficult time deciding what side wall distance to use for this centering measurement. My three options for this side wall distance are from the back wall to:
1. the inside edge of the shower door jam
2. the outside edge of the shower pan
3. the outside edge of the bullnose
I am leaning on #2 which will leave a 4.5″ tile on each side. But close to half of one of those side pieces will be covered by the door jam for 75% of the wall making it look unsymmetrical. It will make the rest of the tile above the door and ceiling look right though IF you don’t count the bullnose. Should I be counting the bullnose? My plan was to purposely stagger the bullnose and field tile horizontal grout lines to help not look like part of the tile pattern. Your professional opinion would be extremely welcomed. Thanks.
Tony Demey
Hi Tony,
I always start with a full tile on the outside edge of the shower pan (inside edge of the bullnose) and cut the inside corner piece. If you want to center the wall I would do the same.
Yes, I’ve read a fair amount of your site and manuals and yes, I absolutely understand the problem of moisture getting trapped and creating a mold sandwich if there is a vapor barrier on both sides of a substrate.
HOWEVER, in one of your witty comments to another question regarding steam shower, you also provide a link to Laticrete’s “Tiled Steam Room and Steam Shower Technical Design Manual”. Please correct me if I’m wrong, but it appears that Laticrete actually recommends a combination of traditional 6 mil plastic behind the cement board AND one of their topical products on the surface.
I want to be able to consider adding a steam generator in a 100 sq ft basement bathroom I am building and now I’m confused. I’ve already got plastic up and can either remove it or slice it, but I’m pretty sure I want to use a liquid topical barrier, such as Redguard too.
Please help me out, oh wise elf.
Hi Jonathon,
Yes, they do require that. Liquid membranes are waterproof, not vapor proof. You need the barrier behind the wall as well. If you are planning on a steam generator then you should have both.
Roger,
I want to install a curbless shower using Kerdi on the floor and walls (new construction). It’s a slab-on-grade with a 4’x4’x 5 1/2″ deep sump. See photos posted as “John’s Curbless Shower”.
Following your eBook, I was going to put the Hardi on the walls first (long enough to embed in the mud deck), and then do the mud deck. Unfortunately, the geometry of my slab & framing complicates this. The framing is not flush with the walls of the sump, and the sump is not square with the walls (it’s cockeyed). In some places, the wall overhangs the sump by 1/2″, and in other places the wall is set back from the sump edge by 0″ to 1 1/8″. The framing is square, so I need to use that for my control dimensions.
So, my questions are:
1) Should I shim the walls 1 1/8″ (or as required) such that the Hardi can lap the sump wall? (each wall is different and cockeyed with the sump).
2) Then install the Hardi, and then pack the deck mud sideways under the bottom edge of the Hardi to accommodate the inconsistencies of the Hardi-to- sump wall dimension (varies 0″ to 1 1/8″)?
3) If I do this, how deep should I embed the Hardi? The deeper I embed, the more likely I’ll have a small void of mud deck on the back side of the Hardi. Is that a problem?
4) Is there a better way to do this?
5) Note that the slab perimeter is level , and top of mud deck will match top of slab. Also, I plan to run Kerdi about a foot onto the bathroom floor, and I will have a glass door.
6) Can I glue the Kerdi drain to my pipe prior to doing the mud deck? I don’t want a void in the deck. If I glue it after (or during) mud deck installation, I have to have a void to get glue on my drain pipe.
7) Would multiple layers of Hardi be better than these very thick shims?
Hi John,
Yes, your plan sounds like it will work just fine. I would embed the backer about an inch or so into the deck, having deck mud behind it won’t hurt anything. Yes, you can glue your kerdi drain in first. Shims are better than multiple layers of hardi.
Roger, thanks for your help.
1)This is my first attempt at posting pictures to your site. Did they make it? I posted 3 photos and a sketch, but I don’t know how to confirm if they actually got there.
2) When I embed the Hardi an inch into the deck, there will be areas where I have a small void behind the Hardi (between Hardi and the wall of my concrete sump). Should I try to stuff mud into these voids so as to give the Hardi some back support?
3) Where shower floor tile (2×2 mosaic) meets bathroom floor tile (18″ Travertine), I may need more than 1/4″ of thinset beneath the mosaics to match the height of the Travertine. If so, should I use some fat mud first so as to hold my thinset to no more than 1/4″ thick?
4) If I decided not to use Kerdi, would this plan work OK with Redguard or Hydroban instead?
5) Is there a particular type of 2×2 mosaic tile that is best for a less-slippery surface?
6) How high should my glass door extend above the shower head?
1. Yes, they always make it.
2. No, the hardi being fastened to the studs is plenty of support.
3. That or use medium-bed mortar instead of thinset beneath the mosaics, that would be a better option.
4. Yes
5. Look for the coefficient of friction number, the higher the number the less slippery the tile.
6. No rules, even or above the shower head.
Thank you Roger. One last issue, please.
1) What is medium-bed mortar?
2) Is it to be used for the entire thickness of the mud deck or just a thin layer to stick on the mosaics?
3) Are you saying I should use medium-bed mortar for the entire shower floor area that is covered by the 2×2 mosaics, or just use it in the small area of concern where the mosaics meet the Travertine?
Note that the only place I have an issue with too-thick thinset is right where mosaic meets Travertine. The rest of the shower floor works OK with 1/8′ to 1/4′ thinset.
1. It is essentially thinset with a lot more sand in it. This prevents shrinking as it cures and allows you to build up the tile more than a thinset would allow.
2. Just to install the mosaics to the height you need.
3. Use it for the entire floor. You don’t have to build it up any thicker than that, but it ALLOWS you to. So it would be like using a thinset that you can build up when and where you need it.
Is “Medium-Bed Mortar” sold under that name, or do you buy regular thinset and add sand (if so, how much do you add)?
Do you lose any strength or other properties by using medium-bed mortar instead of regular thinset?
Thanks for all your advice.
Hi John,
It’s sold under that name, or marble, stone or large-format mortar. You actually gain strength with it.
Which is the better of the two; using a vapor barrier or using Redgard?
Hi Christy,
Redgard, because your waterproofing then sits directly behind your tile and your substrate does not get saturated.
Roger,
I’m about to start tiling the shower and around the tub. Installing 6×8 white subway tiles and will be using 1/16″ spacing. Does it matter whether I use sanded or un-sanded grout? Which is the best way to go?
Once again, thanks for guiding me through this process. I would not have been able to get this done without it.
Roland
Hi Roland,
I prefer sanded, but either will work with that size grout line.
OK. Sanded it is. I had already bought it but wanted to make sure.
Much appreciated.
Roland
Another question..our house was built in about 1960 and has siding on it. It’s that old wide hardboard siding you see so often. We hope to replace it with vinyl this year. We don’t know if they installed a vapor barrier. We are using Redgard on the tub/shower walls. Would it be possible to drill holes in the top plate over that section of the exterior bathroom wall in order to let any moisture escape? As I mentioned before we will have 1/2″ drywall, 1/2″ plaster, mastic, 1/4″ cement board (taped and mudded) , several coats of Redgard, mastic and tile. Thanks for any help.
I hope by ‘mastic’ you mean thinset???
Go ahead and install the redgard, don’t worry about a vapor barrier. If it’s been there for 55 years it isn’t going to affect anything.
Thank you very much! You are great!
Hi Roger,
Thanks for sharing your expertise. You mention cutting slits into the Kraft paper on exterior walls. Going from the inside out, I have studs, plywood (covered in Zinsser mold killing primer), some kind of Tyvek-like foam board, maybe something else?, brick veneer. I suppose I should cut slits in the plywood through the foam bard and whatever else is in my path to the brick veneer? Just a few slits near the top or do I get crazy with it? Thanks in advance!
Hi Ty,
The only thing you’re doing is allowing any trapped vapor between the waterproofing on the face of the board and whatever type of barrier, in this case, craft paper you have over your studs. As long as the craft paper does not seal everything between all the studs you’re fine. Cutting slits in it is the easiest way to accomplish that.