I know there are some people out there (not my regular readers like you!) that read what I write and think to themselves ‘okay, but I’m sure that won’t happen with my installation’. So periodically I’m gonna post things like this that show exactly what happens when things aren’t built correctly. And yes, it will happen to yours, too, if the proper steps aren’t taken. If you care to see more train wrecks you can check out my ‘flawed‘ page wherein I post photos of absolutely horrible tile installations which I’ve torn out and replaced.
See that crack in the tile right there? (The line down the center is not a grout line – it’s a crack. You can click on it for a larger version) That bathroom floor is less than eight months old. It was installed with hardibacker over the subfloor and thinset. At least that part is correct, but that was about it. There was no thinset beneath the hardi and the seams between the sheets were not taped and thinsetted. To a lesser extent the correct screws were not used in the hardi – they committed the cardinal sin of using drywall screws in the backerboard. Yeah. Wrong.
So, back to the crack. (Never thought I’d ever type that!) As soon as I walked in and saw it I knew exactly what was wrong and I knew why. The crack was in an absolutely straight line – a dead giveaway that the crack is likely over a seam in the backerboard which wasn’t taped. If you read my post about how to correctly install flooring backerboards you will see that there needs to be thinset below the boards, the seams need to be taped, and the proper screws need to be used. None of which was done.
And here’s what was beneath it: 
If you click on that photo (I dare you!) you can see the crack follows the seam of the backerboard exactly. Without the tape on the seams the individual boards may move in different directions and, without the support beneath from thinset, they will move independently and eventually crack your tile or, more commonly, your grout lines first.
When you tape and thinset your backerboard seams it will lock the two separate sheets together and any movements in the substrate (seasonal micro-movements, completely normal) will all move as one and in the same direction. This won’t cause any stress on your tile.
I simply pulled up all those cracked pieces and chipped the old thinset out of there, installed proper screws along the seam, taped and mudded the seam (when I say ‘mudded’ the seams I mean thinset) and reset new tiles and grouted it up. Once that grout cures it will lighten and it will look brand new.
So all these little things like ‘tape and mud your backerboard seams’ that I throw out there may seem like it’s just overkill or taking extra precautions which aren’t really necessary – well, they are necessary. And this is why. This will also happen on a shower wall if your seams are not taped and mudded. If the boards move differently it causes uneven stress on your tile – it needs to release somewhere. Ninety seconds worth of work to tape the seam to begin with would have prevented this – just do it! (damnit)
If preventing cracked tile isn’t enough motivation for you maybe this will: all of my regular readers know what happens if your tile or grout crack – your dog will burst into flames! So if you don’t do it for your tile, do it for your pooch. Not only are flaming dogs bad for, well, the dogs, but they tend to run around and catch other stuff on fire too! You don’t want that, do you?
TAPE YOUR SEAMS! 
Thank you for sharing your experience and expertise. I’m doing my first tile job, small bathroom. I pulled the old ceramic tile that was attached directly to a plywood subfloor (not my doing). There is a lot of thin-set mortar residue stuck to the plywood, some of it raised (let’s say a 1/16 of an inch). Is is OK to install the backerboard over this or do I need to remove these? My second question may be difficult to explain, but here it goes. In the old floor there was a crack across several tiles. When I removed the tiles I saw that the crack was right over a seam in the plywood floor. So the crack makes sense. When I install the backerboard I know to avoid seams in the same place as the plywood, but I have a couple of different options in laying the backerboard. The most convenient way would leave about a 5 inch overlap over the plywood seem. is this OK, or should I work the backerboard so that there is more overlap over this section of the plywood, but I would have more backerboard seams in total?
Maybe I’m over thinking this, but I just want to do it correctly.
Thanks!
Hey Craig,
As long as you install thinset high enough to go over those ridges you can put the backer right over it. Five inches isn’t ideal, but it won’t hurt anything as long as you make sure to tape and mud the seams in the backerboard.
Hey Kevin,
If you cut and score it with a blade, as is intended, you will get no dust at all. This only becomes an issue if power tools are used to cut the board. A respirator mask is the minimum requirement when cutting CBU’s with power tools.
Thanks….does Hardibacker need to be wet down before applying thinset….should it be damp while applying thinset?
Hey Kevin,
Yes, but you don’t want the surface to be shiny-wet. You want to wipe it down with a sponge so the backer does not prematurely suck moisture from the thinset and weaken the bond.
In my shower area, I’ll have an outside 90′ corner. Does this get the same treatment as inside corners….mesh tape, thinset and waterproofing? Thanks for all your help.
Hey Kevin,
Yes, if it’s inside your shower you need to do all that to it.
My shower ceiling is Densshield and will not be tiled. How should I prep the surface to be paint ready?
Hi Kevin,
Just use a good primer on it and paint it as you would regular drywall.
Thanks Elf-dude!!!!!
Roger,
I have a poured concrete basement floor that flooded due to a sump pump failure. Normally the basement is dry. I tore up the ruined floating laminate wood floor and I am planning on tiling with porcelain tiles due to the greater durability should I have another flood. The concrete floor is about 15 years old and in excellent shape with the exception of four or five hairline cracks. Can I tile directly over the floor with regular thinset? Do I need to put down a substrate?
Thank you for sharing your knowledge and experience.
Steve
Hey Steve,
While a membrane such as ditra would definitely be best, you can tile directly to the concrete if you want to. I would place at least a crack-suppression membrane over those cracks.
Thanks Roger, but I was hoping you were not going to recommend Ditra. The
basement floor is 365 sq. feet so based on a quick price check that adds
about $500 to the cost of my DIY project. Can I just use Ditra to cover the
cracks or do I really need to cover the whole floor? Is there anything
cheaper that also does the job? In addition, I watched the Schluter-Ditra
video and they mentioned the need for expansion room around the perimeter,
what size gap do I need to leave? Moreover, I assume I need to also keep the
grout out of this gap? I read your memo on expansions seems but I will not
need any because the longest dimension is 21’.
Steve
Hey Steve,
Ditra is not the only crack-suppression membrane out there. You can get some redgard and paint it over those cracks and it will do the same thing, it was actually originally created specifically for that purpose. You can do that and install directly to the concrete. I would leave about 1/4″ around the perimeter of your installation.
Roger,
I am reluctant to use the Redgard (even though it is a cheaper and easier alternative to Ditra) in the basement because if my sump pump fails again the floor may be subjected to hydrostatic pressure. HD sells a thin-set called Flexbond that claims to cover hairline cracks like the ones in my basement slab – do these flexible thin-sets work as advertised?
Steve
Yes they do. As long at your cracks are just cracks, and not uneven, the flexbond should work just fine.
Hi Roger,
Hoping you can help me out with some advice, I am in Brisbane Australia.
My background is in design and construction, but I don’t know all that much about tiling.
I have built a new cottage and in the bathroom I have a shower cubicle in the corner of the room, Imagine an elliptical shaft from floor to ceiling, about three metres high with a portion removed. The construction is 120mm x 38mm cypress pine studs on edge at about 150mm centres with an internal measurement of approx 1020mm x 800mm (standing area). I have sheeted the internal studwork with 9mm bending plywood, fastened with glue and screws with plasterboard suited to bathrooms on the outside curve, the overall construction seems sturdy and pretty straight. Normally we use a material called villaboard to sheet wet areas, it has two recessed edges and is made from waterproof compressed fibre cement. Unfortunately even the 4mm stuff wetted will not go around the tight inside curve of the shower without breaking and it has no recessed edges. I need to find a solution to wetproofing this shower, I want to use the Bizzaza glass mosiac tiles for the finish, they are expensive and I dont want stuff it up or have anything move or any moisture make it’s way through to the frame.
I was thinking of laminating another layer of ply onto the existing layer with plenty of glue (offset from the first), Filling any gaps and fibreglassing the whole internal with several layers of vinyl ester resin (which has some plasticity) and 600gsm fibreglass and throwing kiln dried silica sand into the surface of the resin before it goes off to give the tiles a key (a bit like a swimming pool) I realise this might be a somewhat unconventional approach but I’m running low on ideas. Please let me know if you think I am insane? or can shed any light on this challenge.
Kind regards,
Mike
Hey Mike,
While a viable solution I think the fiberglass with the silica is a lot of work for the same result as using a sheet or liquid membrane. I think either a sheet membrane such as kerdi or a liquid such as redgard or Laticrete Hydroban would be a better, quicker and easier solution. It will conform to absolutely any angle and it’s much easier than fiberglass, and better for the glass as well.
Hey, Roger — thanks for all your great info!
I’m about to tile a mudroom, fairly complicated in outline, with 12″ marble. My joists are 2×10’s on 16″ centers but my subfloor is old planks on the diagonal — most are pretty wide (12″) and some have knotholes upwards of 2″ across. Do you have a particular inclination for the underlayment? A person who is slated to help with the project (and who has done more tiling than I) is talking about just 1/2″ Hardiebacker and then the tile, but I am concerned about stiffness (it’s a bit squishy where the knotholes are near board edges). I’m not eager to go higher than necessary (I’m meeting up with 3/4″ oak), but I figure that’s what interesting threshold profiles are for. Options I’ve considered are the 1/2″ hardiebacker as he suggested, or plywood (not sure how thick would be needed) and then just 1/4″ hardie, or maybe plywood+Ditra… What are your thoughts?
Hoping to avoid tile cracks and pet-conflagrations (no dog, but a pretty flammable cat), I thank you in advance for whatever sage advice and elven jackassery you might send my way!
Be well,
— Maren.
Hey Maren,
You need a sheet of plywood over that to stabilize and strengthen the floor. 1/2″ backerboard adds absolutely no structural support. 3/4″ plywood with ditra would be your best bet to strengthen the floor and minimize height. You may get away with 1/2″ if the vertical planks are very solid overall, but 3/4″ would be better.
P.S. Flammable cats are dangerous animals to have around – just sayin’.
Thanks. I was thinking that might be necessary. If we went with 1/2″ plywood (I think 3/4 might be overkill in the small space), would the Hardie (1/2 or 1/4) be adequate, or would you go with the Ditra? …and why? They seem so different in their functions; the Ditra mainly seems to be for decoupling (of thermal expansion? subfloor spring?), while that’s not at all what the Hardie is about. Also, would the plywood be cut with 1/8″ spacing like Hardiebacker? What type of screws would be used for it? (you’ve mentioned the special cement board screws; elsewhere I’ve seen galvanized deck screws suggested).
Note that I have not thus far ignited the cat. She is fairly cautious around fire, but spontaneous pet-combustion due to buckling tile is another matter entirely!
Muchee thankee,
— Maren.
The 1/2″ will be fine. And so will 1/2″ or 1/4″ hardi – either one. Always attach the hardi with the cement board screws. Galvanized deck screws are recommended by some because they won’t rust or corrode – neither will the cement board screws – and they have the teeth under the head to countersink the screws – galvanized screws do not, they are difficult to get flush.
Ditra simply adds more insurance to your installation by separating any movement in your subfloor from the tile installation. Plywood needs to be installed with 1/8″ gaps at the seams for expansion purposes.
Having laid out my crazy-quilt design over the past few days (in amongst other activities), we embark in earnest tomorrow. I’m leaning toward the Ditra (vs. hardiebacker), in part for insurance and in part for height. Guess I’ll decide for sure tomorrow morning when I’m buying the stuff! (there’s another experienced tile guy at the store with whom I haven’t managed to connect yet.) And a couple more questions, if you have the time…
What type of screws do you recommend for the plywood?
For a mudroom, would you recommend the extra waterproofing of a strip of Kerdi over the seams? (as long as the Ditra makes it generally waterproof)
And there’s no reason to have Hardie in between the plywood and the Ditra, is there? Usually I’ve seen it posed as an either/or proposition.
Thanks for all your tips!
I always use deck screws for my substrate. You don’t really NEED the kerdi-band, but it never hurts. Especially in a room that may see considerable amounts of water over time. And no, you don’t need the backerboard – it won’t do anything for your floor except heighten it if you’re using ditra.
Those were my best guesses, but I wasn’t sure. Thanks!
I’m now trying to figure out which mortars to use (when I should be going to bed; it’s late where you are but quite a bit later here in Pittsburgh!)…
Ditra to plywood is modified, but the answers seem a little more ambiguous beneath the marble. I’ve seen reference to thinset in general being inappropriate for green, black, or red marble — all of which appear in my crazy quilt pattern. OTOH, I’ve seen no reference to epoxy or quick-set mortars in the Ditra lit. O, confusion!
Green and red marbles are known as ‘serpentine’. They are affected by the moisture dissipating from the thinset – it causes them to warp. More specifically, the underside of the marble will be subjected to moisture whereas the top side will not. This inconsistent variation in the moisture will cause the marble to ‘curl’. It’s the weirdest thing you’ll ever see – you don’t want to see it, though.
You can use epoxy or quick-set over ditra without problems. However, quick-set mortar does not negate the curling effect – it will still warp. You need to use epoxy for those marbles if they are serpentines.
I am a few days away from a tile floor installation in my kitchen. There are so many different opinions on proper installation it is making my head spin! I have two reputible installers I am working with and both have a different answer for my exact situation. I was wondering if I could get your opinion.
My home was built in 1960 with very nice, solid construction. The current subfloor is 1 1/2 inches thick (two layers of wood) with a layer of vinyl over the top. The vinyl is original! The floor is in great shape with no issues besides squeaking in 2 areas. The kitchen floor is already 1/4 inch higher than the adjacent dining room.
Installer 1 gave two options. Option1: install 1/4 exterior grade plywood, then 1/4 inch durock with thinset underneath, then the tile. Option 2: install 3/8 in plywood then tile ontop, no cement backerboard.
Installer 2 says: install cement board directly over the vinyl screwed down with no thinset underneath, then lay the tile.
I am concered about floor height. I prefer not to mess with the vinyl as it does have asbestos in it. What do you think of the options presented?
Thanks!!!
Hey Kenzie,
I think the best option is to get 1/4″ durock, install thinset beneath it, and screw it down. At this point you only need a suitable surface for tile installation – the sturdiness of the floor is there. Being that the vinyl is there you need to actually screw something to the floor that will last. Using something like ditra is not an option as the thinset would need to adhere to the vinyl. Thinset beneath the backerboard only supports it fully – it doesn’t need to stick to anything. No need for additional plywood over 1 1/2″ floor.
Thank you for your reply! Your suggestion make the most sense to me. Now how to tell the installer what to do! HA! Wish me luck
P.S. Love the emoticons and the website. Well done!
I’m putting up DensShield on an exterior wall, but before I tear down the 6 mil vapor barrier, is it a ‘Cardinal Sin to leave it up or merely recomended. I don’t see where any moisture would come from to cause mould issues. The DensShield backing would be right up against the 6 mil….Thanks in advance for all of your help…..
Hey Kevin,
With denshield (I still misspell it, normally on purpose) it’s merely recommended. A good compromise before ripping it down would simply be to cut slits in it. This still leaves your barrier but it does give moisture someplace to dissipate. I dunno where the moisture comes from either, but I rip out failed showers like that all the time. They don’t smell good.
At all.
I plan on my shower stall having 2 glass walls and 2 tiled walls. Will it look strange if the ceiling is not tiled. I was thinking of ending the wall tile even with the glass wall height…about 10′ short of the ceiling…..The wife thinks it will look cheap, I’m feverishly searching the ‘net looking for pictures to prove her wrong……..
Hey Kevin,
Keep on looking.
Your both right (how often does that happen???). I don’t think tiling the ceiling is really imperative, it’ll look fine without it, but you really should run the tile up to the ceiling rather than the height of the glass. Think about walking in and looking over the top of the glass – all you’re gonna see is wall. It’ll probably look better with tile at least to the ceiling.
Thanks…
Hi Ceci, yes you need a vapor barrier behind the Hardi unless you are using a liquid applied waterproofing on the face of the Hardi.
Thx for the super fast reply Mike. I have read your article “The importance of a properly installed backerboard” but the reason I asked again was because even the hardibacker co implies that we don’t need a moisture barrier. It says to install one only if the local law requires it?? And of course I have another question
I installed my beautiful 10×20 porcelain linen tiles in the toilet room but after I grouted it the color changed completely from the dark brown I wanted to a super lighter gray wth… 
DId I do something wrong? Do you think after putting a grout sealer it will change back to its original color? Thank you! You guys are awesome!!
Sorry my English is not that good. I meant James Hardy’s website (instead of hardibacker co) and local building code (instead of local law). I’m such a noob…
We know what you meant – we’re noob’s too!
It sounds like it may be efflorescence on your grout Ceci, although I can’t see it from here.
Try to scratch the very top surface of one of the grout lines and see if the darker, correct color is beneath it. Grout sealer will normally not change the color of your grout at all.
Thanks for the advice Roger. Don’t get mad but there are two tilles that are a tiny bit higher than the other and the grout that runs through them has the grout color I want… Im so confused… At first, I thought the grout didnt dry but I already waited 2 days and those two grout lines behind the higher tiles never changed. And you are awesome! I scratched the very top and started to see a darker color. Now what’s efflorescence and how do I solve this? Please don’t tell me I have to scratch the entire grout lines! I have a grout saw (my favorite tool cause it’s got diamonds in it)
You need to scratch every inch of those grout lines with your thumbnail!
Just kidding. You can scrub it down with a 5 : 1 ratio of white vinegar and water and let it dry. If that doesn’t work – try 3:1. If that doesn’t work (or you don’t want to do that) you can try to use a drywall sanding sponge lightly over the grout lines. It’s just like burnt toast – scrape it to the color you like.
Beyond that you’ll need to try sulfamic acid. That’s not really any fun at all. One of the above should take care of it for you.
Hi Roger, your site has helped me so much and I will be coming back as my husband and I keep working on our master bath. I am in charge of the tiling and my husband is doing the rest. We grabbed two hammers on each hand and started demolishing the bathroom and here we are. It’s time to put up the hardibacker inside our double rain shower walls and the guy at Home Depot said that we didnt need any moisture barrier. Is that true? Thanks in advance
Hi Ceci,
No, that is not true. You need waterproofing of some sort in your shower. If you are using a topical membrane such as redgard then it is true that you don’t need a barrier behind it. But short of using a topical membrane you need the barrier behind your backer. Find another guy to get advice from.
(Looks like Mike beat me to it – he’s ninja-quick!
)
Hi Roger,
Question about transition. I’m at the stage of shower installation with tile where I am putting on bullnose at top.I have 6 feet of tile a little below the shower spout and want to finish with bullnose. I have used hardi with vapor and had to cut out about an inch and a half of drywall above hardi and tile to make transition to fit properly.(flatter) The bullnose will be 1 1/2 hardi and I will place mold resistant sheetrock for other 1 1/2 with plastic behind it. Most of thinset will be on hardi and so will bullnose. Other than that I will need to get another 3×5 hardi and cut small strips like sheetrock. Is this acceptable for top very small area. ( very top of my tile work.) I know you like to tile to top but I had ripped out fiberglass shower stall that was at this height and had no moisture problems the past 12 years.
Thanks for all your help.
Dick
Hi Roger
Asked this question the other day but know you are busy or sick of all these questions I have been asking(more than most)
I am at the final stager of my tiled shower and without your help this never would have been possible . I am very happy with the results except for one area.
When I did the floor on the right side I left approximately a 1/2 in gap with 1×1 tile and hardi. When I put the bottom wall pieces about 2 or 3 short ares have a gap that looks like they are even between wall and floor instead of wall completely covering like I thought it would.
it looks fine to everyone but the tiler(me). Should I take out 4-5 small tiles where this is or just caulk?
Your thoughts? Your knowledge has helped many people. WRITE A BOOK SOON!
thanks,
Dick
The drywall will be fine up that high.
Good Day….2 quickie questions….I currently have 5/8 plywood floor, 2×8 on 16″ centres, would like to replace with 3/4″, but have been called, among other names, anal, crazy and #@*!$. Is this a good idea? Also is 1/4 inch CBU acceptable substrate for flooring tile……Many thanks for any advise….
HI Kevin,
3/4″ would be what should be added to the TOP of the 5/8″ to reach a total overall height of a standard double-layer substrate at 1 1/8″. That is the recommended height for a tile installation over a wooden substrate. You aren’t being anal enough.
1/4″ CBU is acceptable – all the deflection strength is due to the substrate below it.
Hi Roger,
I found your site the other day and it convinced me to try my own tile work. In the powder room I am doing I have 3/4″ plywood on top of 5/8″ plywood. I was hoping to remove the 3/4″ layer and put down thick enough cement board so that the final height of my floors would be the same. After reading your last post it sounds like that would be a bad idea… Any good ways to not have a “step up” into the bathroom?
Hey Chris,
Your best bet would be to use a thin substrate such as ditra. Ditra adds about 1/8″ under your tile with thinset and all. You can also use something like tavy thin-skin or a product called protecto-wrap (google those) which will give you an even smaller height. On the plus side you have a very good, proper floor substrate.
Hi Roger, Here’s my situation:
I have some 25-year old tiles that have to go, but I have a question about how to proceed. Here’s the current stackup:
2×10’s on 16″ centers, 5/8″ plywood, plastic sheeting, 1 1/2 square steel mesh nailed on top of plywood, 3/4″ cement, 1/8″ thinset, 1/4″ thick very ugly old tile.
My original intention was to rip it all out right down to the plywood, then go with another sheet of 1/2″ plywood on top of the existing 5/8″, followed by 1/4″ wonderboard (with thinset underneath of course!). But then I got to thinking, do I really need to rip out the cement? The tiles pop off fairly easily, and it’s not too bad to scrape the old thinset off the top of the cement. What do you recommend (cause it seems like one hell of a job to break up all that cement!)
Also I’m planning to go with 18″ square tiles 3/8″ thick with 1/2″ square trowel, but this means the new floor will end up about 1/4″ higher, which screws up a whole bunch of transitions to flooring in other adjacent rooms. Is there anything else I can do to keep the height difference of the new floor down??
Thanks for your advice
Hey Eric,
Congratulations! You have an old-school mud bed there. I still build ’em when people want to pay for them. They are an absolute BITCH to tear out, so if you go that route be sure to eat your wheaties.
If the tiles are coming up fairly easily you can keep the mud bed – it will last – guaranteed. Scrape as much thinset as you can off of it and install your new tile. You have a ready-made bulletproof tile substrate there. Unfortunately there really isn’t much you can do to lower the height of it without compromising the bed. If it is 3/4″ then it is at the lower end of the height required to withstand the stresses, scraping it down will weaken it and may compromise the integrity of your installation. The mud bed should be absolutely flat, though, so you can likely get away with a 3/8 x 3/8 trowel without a problem. Saves you an 1/8″ anyway.
I just wanted to post a quick story here. I am 113 lbs and had this crazy idea to rip out the marble tile in our entry way. BAD IDEA! Actually, it turned out better than I thought… I started by hammering a corner marble piece LOL. Yeah… it only made a loud sound… that’s it. Well, it chipped a little so I couldn’t turn back. I started hammering the grout and little by little I broke a marble tile. What was underneath? I think it’s called felt paper? and concrete?and chicken wire? and more concrete? and thinset? and then… marble. There was no way I could pull out the tiles by itself. I was sooo pissed… remember I’m 113 lbs. I went to the garage and found this huge pry bar ( it looks like a fork) and went at it. I used my head… I cut the chicken wires around the corner and started prying the WHOLE friggin’ floor. Five hours later I was done. I would say the thickness of the concrete and thinset and tile was about 3 in. and real heavy. I had to drag it out the door haha. Now we have a clean plywood floor ready to install a medallion and beautiful emperador marble tile
Awesome! That right there is an old-school mud bed. They are very, very solid – nearly bulletproof. I still do them when I find someone that wants to pay for it. And they are NO fun to tear out. Just think – we build showers like that too – try tearing one of those out.
I know exactly what you mean Roger!! You should definitely charge more for tearing one those out too!
Hi Roger. I had the tile guy come over. Says he layed the hardiboard parallel with the joist and probably should have done it perpendicular because the seems may not have full support of joists. This is why I see a seem. As far as tape goes he says he’s never used it in 14 years! He says in his opinion the tape will raise the seems because the cement board isn’t beveled and the tape will stick up. He is going to reinforce the joist at one of the cracks and re groute and wait a month or so. He also tiled the tile would never crack. He did say he would replace if I dont like it. Just thought I’d share this story. Its crazy how “experts” dont just follow directions and do it right. I may will have to walk threw each process when he redoes it.
Hey Will,
TCNA 2011 Handbook installation standards F144-11 Joists 16″ o.c./plywood subfloor / Cement or Fiber-Cement Backer Board / Ceramic Tile “Leave 1/8″ perimeter movement gap and 1/8″ gap between sheets. Fill joints between sheets solid and tape with portland cement mortar and 2″ alkali-resistant glass fiber mesh tape. Do not fill perimeter joint.”
He’s been doing it incorrectly for 14 years. If the backers are not tapered then he is likely using hardibacker – their website and installation instructions state the same in regards to the mortar beneath and taped seams. The tape leaves a maximum of about 1/16″ height variation over it, unless he’s using a trowel made for vct there’s no way in hell it should affect the installation. Ideally it should be laid perpendicular to the joists, but that likely isn’t the cause although it may be contributing. That alone will rarely cause enough movement to transfer through a 1/2″ backer and crack grout lines.
There are a lot of contractors who do not follow the directions. However, there are a lot that don’t know the directions even exist. They are taught over years how to do something by someone who doesn’t do it correctly. It isn’t always blatant disregard for the standards nor malicious in intent. It is, more often than not, simply lack of training with correct procedures. The fact that he pointed out the direction of the joists tells me he understands how floors work, perhaps he was simply trained by someone not aware of proper procedures.
Thanks for your help. The tile guy is coming today to see what he can do. I told him on the phone I want it all taken out and redone. I’m not sure what hes going to try and fix. Anything “fixed” would just be temporary.
What tape do you recommend for hardiboard? The only thing round here is this USG tape @ lowes. http://www.lowes.com/pd_11548-325-178664021_4294858208_4294937087_?productId=3089933&Ns=p_product_quantity_sold
Hey Will,
Yup, that’s the stuff. A couple of different companies make it but they are all the same stuff.
You mentioned that the above picture didnt use thinset under the cement board or any tape between joints. Did you have to take everything up and start over? Or did your customer just have you fix this problem area and hope for the best on the rest of it? The reason I ask is because I have a new install that has grout cracking. Installer didnt use thinkset between subfloor and hardi backer or tape joints. I took my air register cover and see a seem right at same location of grout seam. Actually we have grout cracks all across tile every 3 tile rows. I think I want to have everything torn out and redone.
Hey Will,
At the time the customer only wanted that particular area fixed – so that’s what I did. This is after reading him the riot act about what’s gonna happen with the rest of it. He called me about a year later and I replaced his whole floor. Some people just need to see proof.
If your grout is cracking every three tiles it’s obvious what’s happening – most backerboards are sold in 3 x 5 foot sheets. It should be taken up and replaced, it won’t get any better and may begin to crack tiles rather than grout eventually.
Firring out studs for backerboard?
This may seem odd – but should/could I cut down strips of 1/4 inch backerboard to fir out the studs or should I just use 1/4 inch plywood? I plan to use 1/4 inch backerboard on top of the firring to roughly match up with 1/2 inch drywall.
I’m firing out the studs because I have a solid surface shower pan which has a two inch or so flange that the backerboard needs to overlap, but not attach, if that makes sense. So question related to that situation, should I do anything to waterproof behind this gap? I was thinking of wrapping the kerdi around the bottom of the backerboard. And how much of a gap should I leave between the bottom of the backerboard and the shower pan?
Thanks – Kevin
Hey Kevin,
You can use 1/4″ backer but it’s difficult to cut into smaller strips and screw through without breaking it. It would be easier to use either drywall shims or firring strips. You can use whatever you want, though, since you’re using kerdi no moisture will get to it. Why aren’t you using regular drywall? That is the recommended substrate for kerdi.
Do not wrap the kerdi around the bottom of the BB. Leave the backer about 1/2″ above the pan and silicone the back of the kerdi to the flange below the backer. This way water runs only into your shower pan.
Roger,
up the installation, if a little water gets back there its less of an issue.
Thanks – will probably go the plywood route, save on the frustration. Even though I have complete faith in the Kerdi system, I’m still weirded out by using drywall as a substrate for a shower, just doesn’t seem right. And when I
On the flange issue, I know not to caulk the bottom of the tile to the pan (to allow moisture to escape), but how much room should I leave? I’m thinking about 3/16 (recommended grout width by the tile manufacturer). I like the silicone idea. I had been racking my brain trying to solve that problem.
Hardi is completely fine for kerdi – drywall is just easier. Make sure you spray or sponge down the backer with water before installing your kerdi. Most backers are thirsty and will prematurely suck moisture out of the thinset. wetting the backer first prevents this.e
You can actually run the tile down to about 1/8″ above the tub rail and caulk that joint provided you leave weep holes in your silicone bead. Read this and it will describe what I mean: Weep holes in tile installations. 3/16″ is pretty huge for that joint. Wait – that didn’t sound right…
Sick of me yet???
We’ll be using ‘Easymat’ in place of cement board under our tile floor. It’s backed with an adhesive & the edges are butted right up against each other. Oh…& it’s quarter inch thick.
Opinions on this product??
Lori
P.S.
How’s the dog?
Hey Lori,
How the hell could I get sick of you?
Easymat does what it’s supposed to do. I no longer use it because I prefer different products, but I have used it and haven’t had any problems with it.
Dog’s fine – I’m about to light his ass on fire myself, he’s being high maintenance tonight. Mutt.
Why is my Kerdi not sticking to the walls? I have a new shower enclosure that I made using Hardibacker for the walls. I sponged down the walls to remove dust and wet the Hardibacker. I applied un-modified thinset with a 3/16 by 1/4 v-notched trowel. Then I used the back of the trowel to smooth it out and get rid of any bubbles. The next day I could remove the Kerdi with very little effort. Any thoughts would be greatly appreciated.
Hi Kevin,
If you are peeling the kerdi off the wall then you’re correct – it will peel off fairly easily – don’t do that.
When the tile is installed it will not be pulling ‘out’ on the kerdi – the weight of the tile will be pulling down on it. The sheer strength of the bond is what you are concerned with. The thinset will continue to grab better onto the kerdi over time, the next day yes, it will be easy to peel off. The tile won’t peel it off. If you want a realistic example of how easily it will come off with the tile grab the sheet of kerdi at the BOTTOM of the wall and pull it STRAIGHT DOWN. I guarantee you it will not peel off.
Over the next 28 days the thinset will get a full cure but you can install tile on it now. Or, you know, after you reinstall the areas you’ve peeled off. Stop doing that.
Wait fer bout a week the try pulling the Kerdi off. It will pull the face of the Hardie right off.
I’m a first time DYI’er and though your website built a customer shower. Got it all done and it looks great, however me not taking the time to read the directions on the sealer bottle didn’t wipe off the streaks on the tile when sealing the wall. Now it’s stuck on there and I cannot find any product o get it off the tile (Even called the sealer manufacturer they reccomended tile stripper) did not work.
Any ideas?
Hey Dan,
Use the same sealer. Applying more sealer on the tile will reactivate the sealer you’ve already applied. It will basically absorb the chemicals in the streaks back into the sealer and as long as you buff it off real well they will disappear.
Oh, and send pictures.
I like to see what you guys build with all my useless information.
Shame on you Roger! Using modified on Schluters stuff!
Hey man – That’s how I roll! It’s an Elf thing, you wouldn’t understand.
For those that don’t know the smart-ass up there busting my balls is Musky Mike from Corrado Custom Tile in Wisconsin – and he does some really nice tile! You can check out his website at CorradoCustomTile.com or just click on his name.
They call him Musky because he fishes a lot – not because he looks like a fish. He looks like a bear.
Like many I’m attempting my first tile job and can’t seem to find my answer in your posts (even though I’m sure its in there). Do I use unmodified thinset to tape my CBU’s joints and modified to put tiles up? If it matters this is for tub walls. Thanks for your time and I really enjoy your site.
Hi Kendall,
Unless you are using Schluter Kerdi as your waterproofing or Schluter Ditra as an underlayment you should not use unmodified for anything (normally). Unless you are installing tile over something orange you should be using modified.
I use modified for almost everything.
Hope that helps. If you have any more questions don’t hesitate to ask.
Thanks Roger, I’ll be using Redguard after I tape and mud the CBU seams. I think thats all I need for now but I’m sure I’ll have many more questions when I start tiling…
Sooo, I guess I jumped the gun a bit with my modified question because at that time I hadn’t even put up my CBU. I just now installed 2 CBU’s on the back wall of the tub (the 5′ portion) one on top of the other. I had already checked to make sure they 2×4’s were plumb and in line w/each other but after installing them the CBU boards are now not plumb. I’m not sure if I can explain this well enough but if I put a 4′ level vertically on it I have about a 1/2″ gap at the seam. It’s almost as if I don’t have enough strength to drive in the screws (not drivewall ones) evenly. My question is..can I correct this problem with extra mud on the tiles to bring them up level or do I have to start all over? Sorry for the lengthy post but I’m really frustrated now and even my glass of Malbec is not helping
Hey Kendall,
You can use thinset to build out the tile but 1/2″, if that is indeed how much difference is there, is too much. It can be done but the problem is that thinset shrinks a bit as it cures. The more thinset you have behind there the more it will shrink. That is a large difference in the center of the boards. It almost sounds as if something is behind the boards at the top or bottom?
It is rare that I actually begin an installation with an absolutely flat substrate, but 1/2″ is somewhat excessive if your studs were plumb and in line. Not sure the reason for that? If it were me I would likely pull them down to see what was going on and shim out where needed. But, if you want, you can leave it as is and simply use thinset to fill in. Entirely up to you. I’d pull them down and fix what needed fixed – after a few more glasses of Malbec, of course.
All I can think of is I’m not getting enough force behind my screwdriver to get it in there (that just sounds wrong on so many levels). I will recheck my work but I think I’m off by 1/2″. So if I do take the CBU’s down can I reuse them even though they’ll have holes from the previous attempt..I’ll be using Redguard once they’re actually up.
Hey Kendall,
Yes, you can reuse the backerboards. It actually may be easier the second time around if you use those same holes for the screws. (talk about wrong on so many levels…) When you reinstall them you will not be trying to drive the screw through the board as well since they’re already there. It may help to get them flat since you don’t need as much force.
Roger, you answered all my previous questions so well. Unfortunately for you I’m back with more. I previously commented in the “Installing cement backerboard for walls” article in case you need to go back and refresh your memory of my project (not that I would wish that on you).
I got the plastic up on the studs, siliconed it (can that even be a verb?), and all the hardiebacker is up except for one small piece. I’m hoping to finish that last piece this weekend and the last wall that needs drywall (it’s a full bathroom remodel) and start tiling the following week.
1. Looking at the tub, the left side wall transitions to drywall (pretty flush transition). I am not sure how to finish that transition. I didn’t want to have to tape it and worry about getting joint compound on the cbu or thin set on the drywall thinking that thin set on drywall would look bad or joint compund on cbu would make the thin set/tile not stick well. I’d like to just end my bullnose tile right at the joint and then caulk it so all you’ll see is drywall, then caulk, then tile. Thoughts?
2. In your How to Install Absolutely Flat Floor Tile article you mention back buttering the tile. I’ve read that some people say you should always back butter even when you thin set the floor or wall and others say that you should only back butter if you are not putting the thin set on your substrate first. My wall tiles are 9″x12″ ceramic with a raised grid (~ 1″) pattern on the back and my floor tiles are 12″x12″ ceramic with a raised small (< 1/2") honeycomb pattern. Do I need to back butter either or is thin setting the wall and floor substrates fine? (Is it me or does back buttering sound delicious?)
3. For the Hardiebacker on my walls should I tape and mud the joints prior to tiling to let it cure or can I do it right before I tile?
4. Do I need to wet either the hardiebacker or back of the tile before I install the tile?
5. I've already put a vapor barrier up so this might be moot but I'm curious. I get that the purpose of the vapor barrier is to stop moisture from reaching the studs because tile and cement grout are not waterproof. If I'm using glazed (glossy) ceramic tile and laticrete spectralock grout isn't that a fairly waterproof surface?
Thanks yet again and hopefully that's it for now.
Hey Tom,
Yes, siliconed can be a verb.
1) It is always better to tape and mud that joint – you can use the drywall mud there, it won’t compromise your adhesion unless you get a lot of it on there. You want to tie those two substrates together so that the joint doesn’t end up cracking.
2) Stop listening to the people that say anything resembling not putting thinset on your substrate first – you need to put thinset on your substrate to fill it in completely and get a good grab. Some guys backbutter everything – I usually only do it when it is a larger format tile, natural stone, or when getting a flat surface is an issue with either the substrate or tile. As long as your substrate is flat you don’t need to backbutter the tile. It is always a good idea, though. Backbuttering is delicious! – Messy, though.
3) You can do it either way. It’s usually easier to do it as you set the tile. If you do it before and everything isn’t absolutely flat it’s a bitch to scrape it down. If you do it when you set the tile it’s easier to fix anything not quite right.
4) I always sponge down hardi before I spread thinset. Hardi is really thirsty – wetting it down slows down the absorption so it doesn’t prematurely suck the moisture out of your thinset and compromise your bond.
5) That is a fairly waterproofed surface. The glazed tiles are not completely waterproof, though. It simply ensures protection for your studs. Think of it as extra insurance.
This’ll be my quickest one yet. Aside from tacking up a level piece of wood where the bottom row will go do you have any tips on preventing wall tiles from sagging? I’ve got hard plastic spacers, not soft rubbery ones so that should help but I may back butter the wall tiles like we talked about above since, regardless of how hard I tried and how much I shimmed the studs, the hardiebacker boards are not perfectly even with each other at the seams. I’m hoping that back buttering will give me a little more forgiveness to try and get the tiles all even with each other but I’m wondering if the extra thinset will make the tiles more likely to sag. I’m planning on using either versabond or laticrete multipurpose if that helps. Also if I already have both of those thin sets at home are they compatible with each other? For example could I start a wall with one and if I run out finish it with the other? Or should I just stick to one brand for the same job? Thanks again.
Hi Tom,
If you have the bottom row of tile supported fully, which the wood will do, and you use hard spacers there is absolutely no way your tiles will sag. Each one will be sitting firmly on hard, non-squishy plastic and have absolutely nowhere to go. They can not sag as long as the bottom row is supported.
You can backbutter or use a larger notched trowel to get the tiles a bit further from the wall and go over the seams. Sometimes you just can’t get the hardi to line up – it happens. You can simply fix it with a bit more thinset behind your tiles. If you stack the tiles correctly they will not sag any more than they would with less thinset.
Every manufacturer recommends using only their thinset from start to finish – every one. That said, I have been in situation where I have had to switch from one to another and yes, laticrete and versabond was one of those situations. It wasn’t a problem – and I’ve never run into a situation where it was a problem. It is always better, though, to stick with the same from start to finish.
Roger,another question (hopefully I will be able to quit asking questions and put all this new found knowledge of the ancients to good use) What brand of thin set would you recommed for setting Ditra over plywood for floor tile and what thin set for 12″ porcelain wall tile in the shower. I have had a few folks recommend Laticrete multipurpose, which I believe is a modified( which Schluter doesn’t recommend for Ditra). Not terribly concerned about cost…more concerned with actually getting this bath done and looking nice.
Thanks again-Jeff
Hey Jeff,
Some of the most readily available thinsets is either VersaBond or Mapei – either of which would work just fine for both applications. Laticrete makes several great products – any of which would also work just fine. The whole modified – unmodified thing with Schluter is something I don’t bother with – I regularly use modified on the products. But Laticrete and Mapei both make good unmodified thinsets as well.