A common misconception about tile and grout is that grout will somehow assist in stabilizing a tile installation. It does not. Unless you use epoxy grout it will add no significant structural elements at all.

So why should I use grout?

Grout is, structurally speaking typing, simply there to fill the spaces between tiles. That is an oversimplification, but it describes the grout’s function. More to the point, it is there to keep other things out of that space. Without grout the possibility of dirt, grime and all sorts of unruly, unwanted things may collect in the spaces between tiles. This may lead to not only unhealthy conditions, but also the chance of damaging your tile while trying to remove those things.

Does epoxy grout help stabilize tile?

If you’ve read any of my other posts regarding grout you have more than likely seen me state that epoxy is different. This subject is no exception.

Epoxy grout will actually add to the stability of your tile installation – to an extent. Epoxy will stabilize only the area between the tiles – the grout lines. It does not stabilize your tile enough to replace proper installation methods. This is not what epoxy grout is intended for.

A couple of reasons for using epoxy grout include the durability, ease of cleaning, and its ability to withstand staining. It is not intended as a product to make a sub-par installation correct.

How does epoxy help?

To the extent that it does stabilize your tile, it will only do so in the direction of the plane. If you think about tile on a floor epoxy grout will not (to any significant amount) stabilize your tile up and down. If you have a corner of your tile that does not have support beneath it, the tile will still crack eventually. It will take a bit longer because of the epoxy, but it will still crack.

If you have two tiles (not installed on anything) that are held together by epoxy grout between them you can grab each end and bust them over your knee like you would bust a baseball bat  (if you were insane) and they would break apart. You can not pull them away from each other and pull them apart – ever. That is the direction of the plane.

So although epoxy grout does add some stabilizing features to your tile installation it should not be used in that capacity.

Grout is an integral part of a correct tile installation but not in a structural way. As you plan your installation keep that in mind and treat your grout simply as an aesthetic part of your overall project. It will not assist in stabilizing any part of your tile. You should only be concerned about the color.

{ 155 comments… add one }

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  • Tara

    Hi Roger,
    I have a pebbled rock shower floor that was fine for a while, however over time some of the pieces have come loose exposing the base in the shower. I have repaired this once before and must have used the wrong tile adhesive I’m guessing. I believe I used thinset mortar. The regrouted and sealed after that. Now, grout pieces and rocks are coming up specifically where the rain shower head hits the floor. There is mold where was rocks once were and I’m wondering where to go from here. Should I rip out the floor and replace the tile board and start over? Or, should I let it dry out, bleach and try it yet once again? Love the look of the rock but feel like overall, this has been a pain in the butt for the areas that see a lot of water. Thank you in advance for your thoughts on this.

    • Roger

      Hi Tara,

      How was the floor installed? Was the thinset mortar (or whatever you used) premixed? In a bucket or a powder you mix with water? There is nothing wrong with those types of pebbles on the floor, it’s the installation method that needs to be remedied. To do that we need to figure out what’s causing the issue.

  • maria

    Hi. I put 4×16 white subway tiles vertical in my stand up shower. I’m really torn between stainmaster epoxy grout and unsanded grout. I’m concerned I won’t be able to work the epoxy fast and correctly. Is this a real concern? Do I just go with what I know and stick with regular grout. Also do I wipe the epoxy right away?

    • Roger

      Hi maria,

      You should probably use unsanded then. Every epoxy is different, I’ve never worked with that one. If you follow the directions TO THE LETTER it’ll be fine. No, you don’t wipe it right away (see above statement).

  • Rebecca Sue Cline Brumfield

    I just had a contracter install tile directly onto the durock. I seen no evidence of any waterproofing. Is there white waterproofing material? When I asked he told me that durock is waterproof and that is sufficient. I’m so sick thinking it’s been done incorrectly and I know there has to be more to make it waterproof than just the adhesive and grout! Please help so I can correct this situation before it’s too late.

    • Roger

      Hi Rebecca,

      No, there is no white waterproofing of which I am aware. As I’m sure you know durock IS NOT waterproof. Grab my free shower waterproofing manual up there on the right, it’ll explain all that stuff. You may end up knowing more than he does, it sounds like you already do, unfortunately.

  • Tracy

    Hello, my contractor used mastic to install tiles in my shower. We noticed early on the tiles took several days to dry. Now our floor tiles on the shower floor have come loose and we removed the entire floor. Do we also need to remove all the tiles on the walls or will we be ok? We spent a lot of money on this renovation and I’m sick over this. My contractor no longer lives in my city. Just my luck.

    • Roger

      Hi Tracy,

      I would at least remove the wall tile a foot or so above the floor. That’s where all the water is going to go, and that’s where mastic causes problems.

      • Tracy

        Hi Roger,

        Thank you so much! One more question… we also have a bench that sits on the side below the shower head. It gets a lot of water but we wipe it down after we shower. Should we replace the tile on the bench too? I can’t thank you enough.


        • Roger

          Yes, you should.

  • Kevin

    I accidentally used sanded grout instead of thin set when mudding and taping my cement backerboard.
    Will it be okay or should I take it off and what is the best way to get it off?

    • Roger

      Hi Kevin,

      Oops. :D You need to remove that. Just sand it off, then go back over with thinset.

  • bee

    my bathroom floor became a disaster with pebble stones they started coming up and the contractor regrouted but that started coming up too..so we ripped up everything i was gonna go with tiles but dont really want them..so im gonna redo the pebbles any recommendations for grout and pebble stones to buy should i use epoxy grout …one other issue we had with the grout was it was a dark brown but when dry would haze over in white..and get mildew in spots that was hard to clean….HELP

    • Roger

      Hi Bee,

      The grout has absolutely nothing at all to do with your pebbles coming up. It is due to incorrect bonding to the substrate (yes, that also causes the tile to crack and come out). If you have someone that knows how to properly install them you can use any grout at all. As far as the white haze – that is likely due to hard minerals in the water you’re using to clean it which remain on the surface of the grout once the water evaporates.

  • Pamela

    Love your site! I just bought a house built in 2008. One bathroom has a tub with a tile surround. In each corner of the tile surround there’s a vertical hairline crack in the grout (from the top of the tile surround down to the tub). The grout lines are very narrow, 1/8 – 1/4″. Do I need to fix this? Do I need to remove the cracked grout and replace it with caulk? Thank you!

  • Dave, a fool

    I did a bathroom floor tile installation IN A MOBILE HOME, using 1/4″ backerboard screwed to the floor joists and 3/4″ particle board.
    Then, I used many-year-old pre-mixed, expired MASTIC to install my large format tiles. I did not backbutter.
    I used epoxy grout from Home Depot, which they no longer carry.
    The bathroom floor tiles have yet to budge. The toilet is solid.
    The tiles are 4 granite slabs.

    Just thought I’d add this comment to the mix.
    I’d definitely not use mastic again, but I can definitely say that the tiles haven’t budged to any noticeable degree despite completely flawed installation practice using mastic.
    Thanks, Floor Elf. With your web site, I was able to do my next floor more properly.

  • Amanda

    Hi Roger,

    I’ve been searching the web for help on installing my river Rock shower floor and tumbled travertine walls. Your site has come up numerous times. I’m wondering if you can help me decide on a few things…
    – should both tile types be sealed even before applying to the thinset?
    – can I use one brand enhancer/sealer for the before grout step and a different brand for the final seal after grout?
    – should I be using epoxy grout for both the river rock and travertine or one or the other?
    Also any brand recommendations would be great!

    • Roger

      Hi Amanda,

      1. No, seal them after they’re set, before you grout.
      2. You can use two different ones, but it’s not really a good idea. Whichever method you choose keep in mind that the first sealer you use will be the one that penetrates the stone. So if you want an enhancing sealer you need to use it first, going over a regular sealer with an enhancing sealer will not work.
      3. Completely up to you, it makes maintenance much easier.

      I prefer spectralock epoxy, and miracle sealants or aquamix sealers.

  • Warren

    Hi Roger,
    How important is the adhesion of tiles to the shower floor bed when laying mosaic tile mats? I have had several individual 1 inch by 2 inch tiles come loose from their mat base. Should I affix the loose tiles by excavating the loose tile base area, apply thin set to the loose individual tiles and install or…. can I position the loose tile and begin the grouting phase?
    Thanks for the great advice Roger.

    • Roger

      Hi Warren,

      You need to remove those and use thinset to bond them. Grout will not bond them to anything.

    • Janelle

      Hi I have river rocks on the bottom of my shower. How can I get them to stick down really well? I’m using thin set mortar. Does it matter if I use an epoxy grout or sanded cement grout? Do I have to seal grout?

      • Roger

        Hi Janelle,

        You can get them to ‘stick down really well’ with the thinset. I believe, however, what you are concerned with is stabilizing them. To do that you need to use enough thinset beneath the rock to come halfway up the bottom of the rock, so it is stabilized all the way up to the sides and there is no ‘cantilever’ motion.

        It does not matter what type of grout you use for them. If you use epoxy it will help stabilize them to a point, but you shouldn’t rely on that. It is up to you whether or not to seal your grout.

  • Connie Smith

    Roger, my husband and I just put in a shower pan with pebbles, he used mortar that a contractor told him to use and we put our pebbles in and pushed them in and waited a little over 48 hours and checked it but several of the pebbles just popped off, most are still secure, can the loose ones be secured back or are we going to have to tear it all out, mortar and pebbles ? We haven’t grouted yet.

    • Roger

      Hi Connie,

      You can just reinstall the loose ones with a little thinset.

      • Connie Smith

        Thank you, it worked.

  • Allen

    It may have been mentioned here or on another thread but something that has come my attention is the use of asbestos in older linoleum and adhesives making removal hazardous. I couldn’t find any definitive guides on identifying them other than black linoleum glue.

    • Roger

      Hi Allen,

      The year of installation will be your biggest clue. And any linoleum tiles that are 8×8 likely contain asbestos. The only definitive method is to have it tested.

  • Nick


    For a pebble type mosaic in the shower floor, I used a 1/4″ x 1/4″ square notch trowel. The pebbles had a mesh on the back but not a lot of thinset squeezed through…adding in additional individual pebbles with back buttering seemed to work ok however.
    My questions are: after installation, I am not confident the pebbles have enough support with the thinset, being roundish and all :-D (you can use that if you want…new word). Should I look for individual pebbles after thinset has cured that are loose and re-adhere them or will the epoxy grout stabilize them enough in a floor installation?
    (Now I’m not talking loose like, you can pick them off the floor…just the shape of the rocks and the limited surface area they have for thinset, does not provide a rock solid embedding in the thinset.)
    Lastly, I was told in the bottom of the 9th, that these types of shower floors hold puddled water and are HARD to keep clean from water deposits etc. What can I do to minimize this potential problem.
    Thanks, as always.


    • Nick

      Update: all of the pebbles feel to be embedded well in thinset…maybe I was just skeptical. After 3 days curing, I’m confident they will be fine.

      I am still interested in your approach to water deposits etc on this type of application.
      Also SpectraLock Premium or Pro? Whats the difference?

      Thanks again!

      • Roger

        Pro and premium are essentially the same.

    • Roger

      Hi Nick,

      If you’re using epoxy grout that will stabilize them. Just make sure you pack it in there well so it gets into all the voids beneath the edges. The only two things you can do to overcome the shape/water issue is to double your slope, which sucks because it feels like you’re standing on a cliff, or not use rounded-top pebbles. At this point your solution would be to simply finish showering, then throw your towel in the shower floor and wipe it down a bit. Problem solved. :D

  • Dave

    Hi Roger,
    My question to you is will grout adhere to thinset residue that is
    not perfectly cleaned off the grout lines? If not can I scrub the edges without compromising the now set up thin set? This is the first time doing tiling of any sort and I want to get it right.

    • Roger

      Hi Dave,

      Yes, it will bond just fine. And any thinset that you decide to scrape out of the grout lines will not affect the thinset bonding the tile whatsoever.

  • Andrea

    HI…purchased a 1″ travertine and slate mosaic for a shower floor. I didn’t realize that the mosaic had no grout line. I can return the tile and pay the hefty restock fee or take the tiles off the netting and individually lay each tile with spacers so it can be grouted. But, what I am really hoping for is some amazing trick of the trade from you.
    Thanks – Andrea

    • Roger

      Hi Andrea,

      No real trick for that, sorry. You can heat up the mesh and it will stretch, you may be able to get them apart enough for a good grout line, but it would be difficult to get them consistent.

  • tom tom

    A guy who tiled my bathroom did what seemed to be a great job. They put pebble tile sheets in floor. After a month the pebbles started coming loose. The more i showered they more they came. I scraped them up and the thin set seemed was white and a little rubbery maybe thats normal. It has new liner with two sheets of heavy plywood under that. They poured the shower basin and it seems fine. I wondered if they used wrong thinset or just didnt get stones in far enough? Either way i have more stone but i thought of just buying square sheets of regular small tiles. Any wisdom?

    • Roger

      Hi Tom,

      They didn’t use thinset – they used mastic. Or, more likely, ‘premixed thinset’, which is mastic with sand in it. It is NOT approved for wet areas, now you know why.

      They used the wrong product, and being a ‘professional’ they should damn well know better. Shit like this is why I began this site. Call whatever supervisor they have and talk to them. If that person does not exist, call them and tell them to fix it. If that is a dead end – call a lawyer. It is NOT acceptable and shit like this gives all of us who care for our trade a bad name.

  • Linda

    We installed small mosaic tiles on our shower floor – there is thinset that has come up between some of the tiles that didn’t get cleaned out and has now dried. Do we need to get this thinset out from between the lines or can we just cover it with grout? Both thinset and grout are while. If we need to removed the thinset, is there a good/easy way to do it?

    I’d really rather just leave it, if possible… I’m awfully tired of this project!! :censored:


    • Roger

      Hi Linda,

      Unfortunately it will need to be removed. Although they are both white, it will never match. White is actually the most difficult color to match. You can get a grout saw and that would be the easiest way to scrape the thinset out of there.

  • Susan

    Hello Roger,
    I have purchased a mosaic tile with very small pieces of marble as a design feature for the floor of a master bathroom. Many of the tile pieces are so close together that it will not allow for grout to get in between them. I am concerned that without enough grout between the small pieces that dirt and or moisture will get in between these small cracks and eventually mold would begin to grow.

    Should I return the tile and redesign my floor? Thanks again for your help :)

    • Roger

      Hi Susan,

      If dirt can get it, grout can get in. :D If you want use your regular sanded grout and, once cured, go over the mosaic with the same color unsanded grout, that will fill in any really tiny gaps the sanded did not get.

      • Susan

        Thanks! The mosaic tile is polished marble – is it okay to use the sanded grout on it?

        Also, on a somewhat unrelated note; I went to a tile laying class where they explained the prep for laying tile on the floor. They suggested the following in this order (up from the subfloor):
        – vapor barrier (will use redgard)
        – self leveling compound if necessary to level floor
        – thin set
        – hardie backer board installed while thin set is still wet
        – thin set
        – schluter ditra
        – thin set
        – tile
        Are all these steps necessary to insure proper installation? What steps do you use to prep for a tile floor?

        Again – ever so grateful for your elfish wisdom!

        • Roger

          Hi Susan,

          Good lord! Are the people running the tiling class trying to sell you product too? (Don’t answer, I already know. :D )

          If you have a wooden subfloor you need a total of 1 1/8″ of ply above the joists. This usually is just an additional layer of 1/2″ over your existing 5/8″ or 3/4″. After that, if you have a crawlspace or other area below from which you need to control vapor entering the structure, then yes, you should use a vapor barrier. But that’s rare (around here, anyway). If, at that point, your floor is out of level MORE THAN 1/2″ you should use slc. If is it not you don’t need to use slc. You DO NOT need hardi beneath ditra, it can be installed directly to your second layer of plywood. Then thinset, then tile.

          So, from the subfloor:
          1/2″ ply


          Don’t forget the beer.

          • Dave

            If you have joists and 5/8 plywood and then deck mix for a shower pan is that okay?

            • Roger

              Hi Dave.


              Shortest. Answer. Ever. :dance:

  • joseph

    Hey devil dog,

    I am going to use spectralock. I have read horror stories about using though. The guy at the local tile supply told me how many SC tile guys dont use it cause its a pain. But I want it for the durability and stain prevention. Can you tell me how to avoid common pitfalls using it such as glazing? Do i wait to wipe with sponge or wipe immediately? Whatever info you can give me, I appreciate.

  • Angelique

    This is interesting! I was just reading questions from people who were asking if they could use clear silicone instead of grout for their glass mosaic tiles. (They weren’t happy with their grout color options.) The people answering the questions all said, “No way! You need grout to stabilize the tiles!” From what you’re saying, that’s not true, BUT I have to worry about moisture getting behind the silicone.

    I’m interested in what you have to say about using 100% clear silicone instead of grout for glass mosaic tiles because I’m planning a bathroom right now, and I’ve found tiles I love, and it would be great if I didn’t have to worry about the way grout will change its look.

    • Roger

      Hi Angelique,

      Grout will, TO A VERY SMALL EXTENT, stabilize the tile. But not in the manner that everyone thinks it will, that’s why I stated that. You DO NOT want to use silicone as grout, especially in glass tile. When water gets behind it, and it will, the silicone will trap it behind there and it will fester. Not only will the tile look funny with random water pools behind it, once the mold begins to grow you’re gonna have a tie-dye looking shower.

      Gross, huh? :D And silicone is not made to be a permanent product, it is made to be removed and replaced as needed. Ever see the bead of silicone in a shower that has begun to pull away from the tub or tile? It does that because over time it will lose elasticity and begin to shrink. So…another reason not to use it.

  • jLo

    Oops! While setting 12×24 tile in a shower, one of the tiles slid down and dried severely out of alignment. Is there any way to remove and replace this tile without compromising the Kerdi Board? …or should I just keep drinking?

    • Roger

      Hi jLo,

      Keep drinking. :D The quicker you get to it the better. You don’t want to pull or pry the tile off, you want to ‘sheer’ it off. Use a drywall or putty knife and a hammer to get it between the tile and board. Sometimes you can save the board, sometimes you need to patch it. But that’s the best way to get it off of there.

  • Mark

    Hi Roger.

    I am having a new bathroom installed at the end of next month.

    I have picked some stainless steel faced tiles for the splash-back behind the new bathroom sink, but due to budget constraints will have to do this bit myself- what started off as a £200 repair to a leaking pipe in the bathroom now requires that the whole room is gutted. The leak had rotted away much of the under floor joists, and so on and so on, and had clearly been leaking away for many years.
    Even the “box” the hot water tank is in now unstable as the bottom of it is a mushroom farm. :shades:
    Now I know why I have had a problem with condensation…… :roll:
    As an aside the leak was not from a defective shower installation, but from a mains-pressure cold water pipe that had rubbed through on a pipe clamp under the floor in the 28+ years since a plumber failed to do the screw up all the way, leaving it to rub on the pipe, and eventually rub trough.

    I am finding it hard to find a grout that is OK for the tiles. They suggest “un-sanded” (grout lines about 3mm) but in the UK grout never seems to say “sanded” or otherwise.
    Tiles here.
    Any suggestions as to what to use that I can actually buy in the UK?

    • Roger

      Hi Mark,

      You can use either type of grout for those. I can’t really be more help as I don’t know what you have available over there. With those size grout lines you can use either type, though.

      • Mark

        Thanks. I Love your honesty, Better to say you aren’t sure than to give bad advice. The sign of a true professional.
        I guess I will just dig a bit deeper into my pockets, and pay to get it done properly with the rest of the work.

  • Joe Halpert

    What is the best grout to use in a tiled swimming pool?

    • Roger

      Hi Joe,

      The guys I know who do swimming pools use epoxy.

  • Megan

    Hi Roger,

    I installed a pebble/river rock tile for a shower pan. 85% of the little rocks were hand laid around the store bought “squares” filling in the gaps. I used Thinset morter to “glue” the rocks to my concrete shower pan (propperly pitched and layered, thanks to your other posts) My next step is to grout however I am seeing some of the rocks are loose and a few have completely popped off, Can I mix up some thinset stick it to the individual rocks and put them back into the pattern? Or do I have to remove all of them and the thinset and start over?

    • Roger

      Hi Megan,

      You can just replace the ones that have come loose.

  • Carly

    Ok….I didn’t want to do this – but I have to. I have adhered 12 x 12 ceramic tiles to a linoleum kitchen floor….using hard as nails. Working very well….but my ceramic tiles were caught in the rain (storm) a few days before I laid them and must have still had enough water remaining in the ceramic to cause a problem. Tiles laid perfectly. Stuck nearly instantly. In the morning….knock knock…half of them hollow. I have popped the hollow ones up and let the dry…..and easily scraped the water affected hard as nails off the floor. Have cleaned etc and ready to go again….but before I do…I am open to hearing about the holes in my logic and wondering if I should pull them all up in the efforts to ensure they are all dry through.

    My biggest question is: what grout will be the best? I don’t know if I require one with some flexibility – as I want to create the strongest bond possible between the tiles without cracking.

    Any advice, comments, or scornful opinions welcome. Im not trying to reinvent the wheel or build a castle that will be here in 300 years – just want a floor that I dont need to fix every other day for a couple of years until this house is bulldozed.

    • Roger

      Hi Carly,

      You’re not going to get a grout that will not crack. Even flexibility won’t last in that application (and they are hard to find and expensive). You already know the flaw in the logic, that’s why you typed the first sentence. :D It is simply not a proper application nor correct products, an inferior, unstable substrate improper bonding products. I honestly don’t know what to tell you to use, nothing I’m aware of will last there.

      • Carly

        Thought so. I hate it when Im right about being wrong.

        So, here’s what I’m going to do…..please bear with me. I have, in the meantime between my post and your’s – reglued the tiles that lifted. They’re not going anywhere for a loooong looong time. I know it’s not the right way to do it – but it’s working for now.

        So, if just for a minute we pretend (give me a break, I’m a girl) that there are no holes in my theory – what would be the most effective grout to use? Also – here’s another thought to throw at you….would using a piping bag to get the grout in and around and little spaces around the tiles be of any benefit or greater ease at all? It seems like it may be a little less messy and more effective?

        Thanks Roger!

        • Roger

          Use a urethane grout. No, a bag would take more time, be more tedious and difficult, and actually lead to less grout in the small spaces.

          • Carly

            Hi Roger,

            Thank you very much for your advice. Guess what we did….pulled them all up – and pulled the linoleum off the floor….sigh….and we now have a proper floor to adhere the tiles to….with real mortar….and will then use real grout. Why oh why can we send a man to the moon and not have an easier method to stick something to the floor?

            • Roger

              It is easy, you just need to remove the existing flooring first. If that’s done there’s nothing terribly difficult about it at all.

              If you have any more questions can you PLEASE post them as a reply to my answers? I have (literally) over 15,000 questions and answers here, when you start a comment like ‘guess what we did, pulled them all up…’ I need to go searching for your name and email address, find the comment, read it and my answer, then I can begin reading the second sentence because I know what the hell I’m reading about. :D Thanks.