Cracked floor tile due to improper substrate preparationI 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: Improperly prepared substrate beneath cracked floor tile

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.

Repaired floor tileSo 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! :D

{ 543 comments… add one }

Leave a Comment

  • Corey esamann

    Sorry roger, upstairs BATHROOM, not basement!! :lol2:

    Reply
  • Corey esamann

    Hi Roger,

    Great articles here! Quick question. My house is 1940’s and I pulled up 6×6 ceramic tiles along with hardi backer board from our upstairs basement. Underneath is what looks like a plywood subfloor of different colors of wood, some look older and some came up with the backer. Can I simply use the thinset applied under the new hardi backer I’ll put down, as a way to fill in those gaps and low spots in the subfloor? Thanks!

    Reply
    • Roger

      Hi Corey,

      Normally, yes you can.

      Reply
  • Jim

    I am tiling a basement bathroom. It’s new construction and the concrete floor is very level. I waterproofed the concrete using Olympic waterseal when I first moved in 7 months ago. In order to ensure an enduring tile installation, what should I use, or do to the concrete, to make sure the tiles will adhere to the waterproofed concrete.
    Thanks for your response.
    Jim

    Reply
    • Roger

      Hi Jim,

      You can either scarify the surface to remove the sealer (until water splashed on it soaks in within a minute) or you can go over it with a primer like Mapei prim-grip, and tile right over that.

      Reply
  • Rookie Steve

    I feel like an idiot… had to get that out of the way.

    thinking I was a pro after helping my son with our first simple tile job on a slab… I attacked my own bathroom project. Subfloor is 3/4 ply and I bought 1/4 hardi. There were some uneven areas/valleys and so I applied thin set (1st time) to those areas. However, I didn’t mix properly (not enough water). So now i have some hills in a few locations and that is causing the hardi to not lay completely flat. I tried wire wheeling the raised areas with minimal impact, tried belt sanding with minimal impact.

    I see one primary option… add more thin set to cover the entire area to be tiled.

    So here is my question(s):

    1 – if i do that should i still use the hardi?

    2 – any other options that you can think of?

    Thanks for the assist…

    steve

    Reply
    • Roger

      Hi Steve,

      No worries, I feel like an idiot daily. :D

      You could use slc (self-leveling cement), you could float it out with thinset to make it flat (no more cement board over it), or you could just get it flattened out beneath the tile as you set it. Those are in order of ease, slc the easiest.

      Reply
  • Mark

    I am putting down 1/4” hardibacker in our bathroom floor. I have a lot of kerdi membrane left over from the shower. Can I cut it into strips and use it as a substitute for the fiberglass tape on the seams? Thanks, you have a very informative site.

    Reply
    • Roger

      Hi Mark,

      Yes, you can.

      Reply
  • Nate

    What is the best sub-floor to use under vinyl tiles in an upstairs half-bath? I was thinking about 1/4 cement board on top of the original wood plank floor. The house was built in the early 50’s and I already scraped up the old 1970s looking vinyl floor. I still might use actual tiles instead of the vinyl. I was just looking for an inexpensive easy remodel job so I choose vinyl tiles.

    Reply
    • Roger

      Hi Nate,

      1/4 backer will work fine.

      Reply
      • Nate

        Thank you so much for your reply! I was just afraid 1/4 would be to thin and not smooth enough but I think I’m going to go with it. I was looking at the 1/4 Hardie backer at Home Depot. The room it self is only 61×71 inches.

        Reply
      • Nate

        One more thing. I should “mud” the backer board to the original wood plank floor in addition to securing it with screws correct?

        Reply
        • Roger

          Yes, that fills any voids and ensures full support. It doesn’t have to bond to the plank, it just has to completely support the backer.

          Reply
  • Jaypaxton

    Roger,

    In your example above you said the Hardi Backer was not mudded to the subfloor. In your fix it sounds like your couldn’t re-do that part. Are you comfortable your fix will hold without the Hardi being installed correctly.

    Reply
    • Roger

      Hi Jay,

      Nope, not at all. I knew it, the builder knew it, I even told a couple random people on the street I wasn’t responsible for it. I told them exactly what was wrong before I even removed the tile. But this was done when I was working through a shop and they just wanted it fixed, so I fixed it. :D

      Reply
  • Boot Pierce

    Roger,

    I have my backer board, thinset, tape and etc. ready to go. I have a a floor with 15/32 undelayment over OSB. I was planning (for height match reasons) to remove the 15/32 underlayment and set the 1/2 inch backer board. Is it okay to put thinset directly on the OBS subfloor or should I leave the underlayment? My fear is that it will never come off the OSB in the future if it needs to be replaced.

    thanks in advance for your help

    Reply
    • Roger

      Hi Boot,

      You need to leave the underlayment there. Your tile needs a double layer beneath your backer, which you currently have. Backer has no discernible structural properties to it, the underlayment does. Never compromise your tile installation and substrate for height differences, use some type of transition strip. If you need to save height you can use ditra or 1/4″ backer.

      Reply
      • Scott Lindner

        I’m a DIYer new to tile. I am about to tile a tub surround and a floor. I have the vinyl floor and underlayment ripped up. Just the subfloor at the moment. Do I need underlayment on top of the subfloor prior to the thinset and backer board? Most references I have found state to thinset directly to the subfloor. If I do need underlayment, what product do you recommend for a newbie that’s more concerned with ease of installation and quality than overall cost?

        Reply
        • Scott Lindner

          Let me clarify. It seems as if some refer to the event board as the underlayment but your response above suggests a different underlayment prior to installing the cement board.

          Reply
          • Roger

            If you do want to use the backer then I would still suggest an additional layer of ply beneath it. If you are using ceramic or porcelain and have 19.2 or closer OC joists, you don’t need the additional ply.

            Reply
        • Roger

          Hi Scott,

          If cost is not a factor I would recommend an additional layer of plywood, then ditra. The cost of ditra is not significantly over the cost of underlayment, although it is a bit more. The advantages are well worth it, though, as is the ease of use.

          Reply
  • Joe

    Interested in installing kitchen porcelain tile with 1/2 inch cement board next to existing hardwood flooring (3/4 inch) of adjacent room. Can I get away without a transition strip on top of both and still only get a minimal height difference? Or do I need to go to 1/4 inch cement board for a more seamless transition (but end up loosing some strength)? Thanks.

    Reply
    • Roger

      Hi Joe,

      You can do it without a transition strip if you want. You WILL NOT lose any strength at all using 1/4″ backer, no backer adds any significant structural strength.

      Reply
      • Joe

        Therefore, is there ANY benefit to increasing from using 1/4 inch backer to 1/2 inch, other than if need more/less height? Thanks.

        Reply
  • Ron

    Taping the joints of hardi with what type of mesh tape? Is it the same type use in Sheetrock? I’m have a hard time understanding how this ties the sheets together seeing how the tape has such little strength. Am I missing something? And is it always important to use thinset under hardi backer? And one more question, Hardi Backer or Wonder Board?

    Reply
    • Roger

      Hi Ron,

      Alkali-resistant mesh tape, it’s found in the tile section. It looks the same as drywall mesh tape, but it isn’t. The tape connects the two sheets so they move as one in a linear direction, if you try ripping a piece of that tape in half you’ll find out how strong it is for that application.

      YES! It is ALWAYS important. Always.

      I prefer wonder board, but both work well.

      Reply
  • dave cerenzia

    been in the tile business for 45 years. I have never taped a floor joint with mesh tape. I USE A QUATER NOTCH TROWEL AND INCH AND HALF COILROOFING NAILS . NEVER HAD A PROBLEM

    Reply
    • Roger

      Well hi Dave,

      WHY THE FUCK ARE YOU YELLING ON MY BLOG???

      Being in the tile business for 45 years you may not realize this – typing in all caps constitutes yelling on the internet. Please don’t yell at me, it tends to piss me off.

      I’m assuming that you’ve never had anyone call you back in 45 years to tell you their floor is cracking. I’m also assuming that’s why you’re assuming you’ve never had a problem. Good for you – ignorance IS bliss sometimes, isn’t it?

      Just because no one has called you back to fix something that you’ve fucked up doesn’t mean you have never had a problem, it means those people didn’t call you to fix what you fucked up. Get it? :D So take your ego and your magic coilroofing nails and fuck off with ‘ya.

      Now, if you would have bothered to read around a bit before attempting to troll ME on MY website, you may have discovered a few things:

      First, everyone who reads here regularly already knows you’re full of shit. It’s the old ‘I’ve been doing this for a thousand years AND NEVER HAD A PROBLEM’ line. It’s bullshit. You know it, I know it and all my readers know it.

      Secondly, I am more than happy to have a RATIONAL conversation with any point I make with which you may disagree. But if you come onto my blog and act like an ass, or ‘yell’ without provocation, that particular conversation is off the table.

      Lastly, any installation methods I state, or installation methods I repeat, including taping floor joints, are standards set forth by the TCNA and ANSI tile installation standards handbook, something with which you are obviously unfamiliar.

      Tell you what, if you’re so adamant about not having any problems, ever, why haven’t you shown up at a TCNA technical committee meeting and made your case? We would have listened. But you didn’t do that, did you? Please, continue to NOT tape your seams, continue to do things improperly, continue to believe that you’ve NEVER HAD A PROBLEM with those improper methods.

      It keeps guys like you happy and guys like me in business.

      Have a fabulous weekend! :D

      Reply
  • tauran

    Roger, do you mud over hardi backer screws or do you just need to tape and mud seams?

    Reply
    • Roger

      Hi Tauran,

      Just the seams.

      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.

      Reply
  • joe

    Replacing vinyl in kitchen and sunroom with porcelain. Sits currently about 1/2 inch less than hardwood floors in adjacent room. Under vinyl I have luan then about 3/4 inch OSB above floor joists / crawl space. Very slight unlevel/hump in one area. Removing vinyl and luan. Received 3 quotes: one said 1/4 inch wonderboard, another said 1/2 inch wonderboard, and one quoted Strata Mat on top of OSB with no additional plywood or board. Making sense? Any preference? Best for customer? Any cost differential?
    Thanks.

    Reply
    • Roger

      Hi Joe,

      Any of them will work, but they ALL need an additional layer of 1/2″ ply beneath them.

      Reply
  • Bill

    Hi Roger,

    I’m building a walk in smoke house with 2×12 Walls (reclaimed roofing materials). Because of the fire concern and cleanability I want to line the inside with concrete board and ceramic. The idea is the inside should never get above 220 degrees so unless there is a grease fire I should be safe.
    So my question is about the vertical walls and ceiling, do I put a moisture barrier (aluminum) behind the concrete board and do I just put on thin set and go or do I need something other than thin set for the heat?

    Reply
    • Roger

      Hi Bill,

      Just thinset and go. Using aluminum behind the backer would defeat the purpose anyway. :D

      Reply
  • Bailey

    Hi! We laid Hardibacker board over a wood subfloor a few days ago. When tapping the seams, I noticed that one corner of the backerboard is quite a bit unlevel. It is too hard now to redo. Can I simply hammer that corner down, vacuum up and loose material and apply more thinset to even the surface out?

    Additionally, what is the consequence if 4 corners of the backerboard happen to line up? I have a stubborn husband that wouldn’t listen to me on that one so he will be re-doing the floor if there are any issues.

    Thanks!

    Reply
    • Roger

      Hi Bailey,

      Yes, but don’t tell anyone I told you that. :D Four corners in one spot creates a weak spot in your substrate where it is both not as sturdy as the rest of the floor as well as a pinpoint area where expansion of all four sheets could cause an issue – even when taped and mudded.

      Reply
  • Nick

    I am planning to apply mesh tape and thinset to the joints and seams of the cement board in my shower, but I would also like to use one of the liquid waterproofing products in those areas as well. The product’s instructions mention the optional use of a fiberglass reinforcing fabric. My question is – could you skip the use of the mesh tape when applying the thinset to the joints and seams if you are embedding this fiberglass fabric in the waterproofing product in those same areas? Or would you apply both the mesh tape with the thinset and then apply the fabric and waterproofing over the whole lot (seems like you could end up with quite a hump)? Or skip the fabric all together? Thanks – I enjoy getting my education with your mix of knowledge and humor. Keep up the good work.

    Reply
    • Nick

      Submitted my question before scrolling through the comments – is Ryan, in the last post, asking the same question? Sounds like your answer is to use both the mesh joint tape with the thinset application and the fiberglass fabric with the waterproofing product.

      Reply
      • Roger

        I told Ryan the same. You normally won’t tape and mud the wall/floor transition or the drain, so you still need the fabric there with the liquid.

        Reply
    • Roger

      Hi Nick,

      Only use the mesh tape when you tape and mud the seams (just using thinset doesn’t do what it needs to). Once that’s cured you already have the fabric reinforcement over the seams. You should still use fabric reinforcement at the wall/floor transition as well as around the drain.

      Reply
  • Julie

    Hi Roger,

    Do I need to use plastic vapor barrier behind 1/2″ Hardibacker board in my tub/shower combo if I’m using Kerdi over the Hardibacker?

    Thanks for your help! You’re awesome!

    Julie

    Reply
    • Roger

      Hi Julie,

      Nope.

      Reply
  • anthony

    Hi Roger,

    I posted a few months back regarding our travertine stone tile floors cracking in near exact 4’x8′ patterns matching the OSB panel joints. This occurred in 2 bathrooms and a laundry room. I just removed a tile and checked subfloor panels (from crawlspace access) – my findings are included below.

    Facts:

    Tile floor assembly has single-panel 23/32″ OSB T&G subfloor with 1/4″ CBU over wood framing (2/12″ EW Joist, 16″OC) that’s better than L/720.

    Cracks formed directly over single subfloor panel joints (4’x8′ pattern) and are indented, concave depressions about 1/16″ max depth.

    The cracks weren’t observed until ~ 6 years after tile installation (new home) and slowly formed over this past year.

    We lived in home full-time for first 3 years (two adults, foot traffic light), but for the past 4 years we have only utilized home on weekends (very light traffic). While away we use HVAC to keep home between 50F-82F.

    Builder did not install a vapor barrier in crawlspace and the home is on a sloped lot. Moisture levels in crawlspace were so high they distressed adjacent hardwood floors. We installed a vapor barrier and increased crawlspace ventilation about 2 years before tile cracks started.

    Tile was hard-grouted at perimeters instead of using expansion joints.

    Findings when tile removed and subfloor checked:
    a) As suspected, cracks were directly above subfloor panel edge and end joints;

    b) Thin-set mortar beneath backer board was extremely thin, 1/16″ thick at best.

    c) CBU seams were butted, not gapped, however seams were taped.

    d) CBU board was cracked (not at seam) beneath tile crack. So was thin-set of course.

    d) Backer board was not wet sponged as evidenced by significant cement dust which made for poor bond with thin-set.

    e) “Patty” method used on top of troweled thin-set (~3/32″) beneath tiles – one “dab” at corners and one in middle of tile. Coverage was only about 30%! (Hard to believe this didn’t cause tiles to crack early on!)

    f) Subfloor panel edges were checked from crawlspace access. Edges beneath tile cracks are warped or buckled. Buckling at the panel edges is a downward sagging, concave shape measuring about .065″, very similar to tile indented fractures. Couldn’t check panel ends since the joists hide them. Buckling likely occurred as OSB dried out after the vapor barrier and ventilation was increased.

    I would appreciate your insight as to:
    1) why cracks formed only above subfloor edges and not over CBU seams as well;
    2) Why it took so long to crack given how poorly it was installed, and
    3) What would you suggest as best installation method for new stone tile assuming we re-use 3/4″ OSB subfloor.

    Sorry for this lengthy post. I’m still puzzled why the floor took so long to fail, especially given how poorly it was installed, and wanted to provide you with all the details. Shorten for posting as you like.

    Looking forward to your inputs.

    Thanks,
    Anthony

    Reply
    • Roger

      Hi Anthony,

      It seems to me that the amount of time is due to the time it took for the moisture which was being absorbed by the subfloor (due to lack of vapor barrier) to warp the edges enough to cause significant failure of support beneath the backer in those areas. The reason it cracked over the subfloor rather than the cbu is because the cbu seams were taped and mudded, thus a monolithic structure at that point.

      I have absolutely no idea why it took so long to fail, but as I’ve always said, it will fail if the five-spot method is used on a floor – EVERY TIME.

      Since you’ve installed a vapor barrier I believe you’ve essentially eliminated the source of the problem. Any proper method would be just fine with your framing specs. I would probably do an additional layer of 1/2″ ply over the osb, then ditra, then tile.

      Reply
      • Anthony

        Roger,

        Thanks so much for your input and timely response. I like your idea of adding plywood underlayment and ditra, so we’ll likely go with that. Your passion in your work and commitment to help others solve problems are inspiring. Keep up the great work as it helps many of us sleep a little better at night.

        Thanks again,

        Anthony

        Reply
  • Andrew

    Hi Roger,

    Very helpful site! Thanks!! Quick question, we are putting in a new neo-angle shower with a fiberglass base and tiling the walls. I installed hardiebacker 500 over the weekend and tape the joints last night with proper cement board tape. My question is do I need to mud (thinset) the joints prior to tiling or is the thinset used when tiling sufficent? I was thinking I needed to do it seperate, but someone mentioned that you can combine that step. Thanks!

    Reply
    • Roger

      Hi Andrew,

      You can do it as you set the tile.

      Reply
  • Charles

    Hi Roger,

    1. Heard porcelain was brittle as heck. Scared now as the cutting stage is comin up. Any tips to share for avoiding chip- out at the wet saw? Should I do finish cut first, then do a regular cut? I do know to go slow and not to push the tile into the saw.

    2. How to remove thresholds safely? I got a thin strip of what looks like laminate wood held down by 5 finishing nails/brads across it. I’ve got a small pry bar which worked great for the base, but not sure about the best way to proceed with the threshold w/o damaging it. I’m doing a kitchen.

    Thanks mightily,

    Charles

    Reply
    • Charles

      Update: The threshold turned out to be as straightforward as the baseboard. Soon after posting, I tried just finesse it up, applying gentle pressure on either side of the finish nails and out it came.

      I’m going to read up on your transitions post to get ready for handling the laminate flooring and tile transition for the kitchen.

      Charles

      Reply
      • Roger

        So no glue? Good! :D

        Reply
    • Roger

      Hi Charles,

      1. I don’t know who told you that but it isn’t true for most porcelain. If it is not annealed (cooled) correctly yes, it can be brittle. But it’s not normal. Usually only with the really cheap stuff. A finish cut and then the full cut works best on the brittle stuff.

      2. Just get right under the nails and pry up slowly from there. Cross your fingers that it isn’t glued down as well. If it is you’re replacing it anyway.

      Reply
  • Charles

    Roger,

    Thanks for everything you do in diffusing tile knowledge and your great help to us going it alone. Just was wondering if Ditra, the orange mat stuff will give me the valid substrate I need to put the porcelain tile over the vinyl floor?

    Thanks again!

    Charles

    Reply
    • Roger

      Hi Charles,

      Yes, it absolutely will. But the vinyl needs to be removed as well as any thin plywood luan that is likely beneath it. Most vinyl is cushioned which leads to movement and traffic patterns which will eventually crack the grout. Once that’s gone you can install your ditra then porcelain.

      Reply
      • Charles

        Thank you, Roger, once again for sharing your perspicacity and knowledge into all things tile, and doing it with humor. I think I’m gonna stick around here.

        With gratitude,

        Charles

        Reply
  • Charles

    I have a vinyl floor approx. 180 sq. ft. that I’m about to set porcelain tile over. I know through reading your entries that a professional installation mandates that I should either tear-out the old vinyl floor, install backer board, and then lay the tile, or install backer board over the vinyl, then the tile.

    But what if I have certain budget constraints…namely time and money…and don’t want to install any backer board?
    1. Can I lay the tile right over the vinyl? Will the tile stick?
    2. Is there a risk of it cracking in 8 months?
    3. Is vinyl ever an acceptable substrate for tile?

    I would follow all other correct methods and techniques, such as thin set under the backer, correct screw types and placement, taping of seams, thin set on top of seams, and finally thin set on top of the backer board for the substrate.

    Thanks,

    Charles

    Reply
    • Roger

      Hi Charles,

      1. No. If the proper thinset is used, yes, it will stick.
      2. Yes.
      3. No, not in my opinion. Not without backerboard over it.

      Reply
      • Charles

        Thanks Roger. Let’s suppose for a sec I went on the fool’s errand and put the tile over the vinyl with no backerboard. Should I use modified thin set instead of unmodified to make sure it sticks?

        Reply
        • Roger

          Yes, modified. It may then last 4 weeks rather than only 2. :D

          Reply
  • Angelique

    I just read your waterproofing manual. Have you ever used magnesium (MgO) board rather than standard cement board? We’re planning to do our shower with the traditional method. We’re using a Tu-Tuff polyethylene vapor barrier.

    Reply
    • Roger

      Hi Angelique,

      I have used magboard. I like it a lot, it’s just difficult to find around here so I don’t use it that much.

      Reply
  • CDE

    My mother would like to replace the original tile floor in her bathroom with new porcelain tile. The floor is 40 square feet. The house is a bi-level in NJ built in 1970. The bathroom room is on the main floor with the garage below it.

    I removed a couple of tiles to see what is underneath and I had a tile contractor at the house today. He said that he would do the following:

    1. Remove the rest of the floor tiles
    2. Spread the thinset on top of what he called the existing “mud” base that the original tiles were placed on.
    4. The floor is not flat, there is a little bit of bevel in it. He said he would “build up” the floor to flatten with what I am assuming is the thinset.
    3. Put the new tiles on top of the new thinset.

    Kindly seeking your thoughts and input on what the contractor said and how this job should be done properly.

    Thank you for your time and assistance.

    Reply
    • Roger

      Hi CDE,

      If it is a mud bed then his technique is correct. Sounds like he knows what he’s doing. :D

      Reply
  • Ryan

    Hi.
    I’m using the redguard method for my shower. Installing half inch tile backer and applying three coats of redguard over the backerboard. I’m using mesh tape approved by redguard in all the corners and field joints. Do I still need to apply cement backerboard tape and thinset to all the backerboard prior to applying the redguard or will the redguard act to bond the backerboard sheets together?

    Thanks.
    Ryan.

    Reply
    • Roger

      Hi Ryan,

      The mesh tape you are speaking of is to strengthen the redgard at joints and around the drain. You still need to tape and mud the seams and corners.

      Reply