The days of grabbing a three dollar bag of “thinset” and sticking floor tile right to the plywood in a bathroom are long gone (for professionals, anyway). For a proper tile installation you need a proper substrate. One of the most readily available are cement backerboards. These include products such as Hardiebacker, Durock, Fiberboard, wonderboard and a host of others.
When properly installed on your floor it is an ideal tile substrate for a quality and lasting installation. Notice I said typed “properly installed”? Laying them down on the floor and shooting drywall screws through them does not constitute proper installation.
Choose your weapon. I prefer Hardiebacker or Fiberboard. Whichever you choose make sure you get the proper thickness. With rare exception the 1/2″ variety would be the best choice simply because I like to overbuild stuff. With proper floor framing and deflection ratios, though, you can use 1/4″ to minimize height differences. This is not to say that 1/2″ adds significant sturdiness to your floor – it does not.
Dry fitting Backerboard on floor
You need to realize that cement backerboards, or just about any tile flooring substrate, does not add deflection stability to your floor. That is the up and down movement in your floor when you walk, jump, or use a pogo stick on your floor. The backerboards will not significantly diminish that movement. This needs to be addressed by adjusting your floor joists and framing – not by adding stuff on top of them. If your floor is bouncy without the backerboards it will still be bouncy with them.
Bouncy is not good for tile. (There’s a sentence I never thought I would say type.) I will, however, address deflection ratio in another post.
Start by ‘dry fitting’ all your pieces. This simply means cut and lay your pieces into the room without attaching them. Get all your pieces cut, holes cut out, and doorways undercut to fit and lay everything in there just like it will be when installed. This saves a load of time, mess, and headaches.
Backerboards dry fitted - notice gaps in seams
The joints in backerboards should be staggered. that just means that none of the seams should line up across the room and no four corners should be placed together. By staggering the seams you add strength to the installation simply by not having a significant weak point in the substrate.
You also want to leave 1/16 to 1/8 inch gap between each sheet – do not butt them together, and around the perimeter. If you butt them together you leave no room for expansion. The backerboard will not expand, but your walls will. If everything is butted tight and your wall expands into the room guess what happens. That’s right, your dog may burst into flames and no one wants that! It will also cause your floor to pop loose and possibly ‘tent’ or peak at the seams.
Beneath the backerboards you need thinset. Just about any thinset will work but you need to have it there. skipping this step virtually eliminates the purpose of preparing your substrate for tile – you may as well go grab that three dollar bag and start setting tile now. You need it – really.
Installing thinset beneath backerboards
Now that you have them all laid in there properly pick one side of the room to start on and pull a row out. You should only pull out one row at a time to place thinset beneath. That way you can replace them easier and in the proper position. If you pull out the entire room you may get to the last piece and discover everything has shifted 1/2″ and the last piece needs to be cut again. Not really a big deal but you won’t realize it until the backside of it is covered with thinset and you now need to pull it up, wipe the thinset off the wall from pulling it up, cut it, clean the thinset off your saw, snuff out the flames engulfing your dog (again), and replace it. It’s a bit easier just to pull one row at a time.
You need to trowel thinset onto your floor. I cannot overemphasize this (well, I could but you’d get sick of hearing it). This step is imperative for a proper tile installation. The thinset is not meant to ‘stick down’, adhere, or otherwise attach your backerboard to your subfloor. It is simply put in place to eliminate voids beneath your backerboard. Once laid into the thinset bed the floor becomes a solid, fully supported substrate for your tile – that’s what you want.
If you have an air pocket or some certain spot in your floor that is not level or flat with the surrounding area and you simply screw your backerboard onto it this will create a weak spot in your floor. Constantly stepping on that spot will, over time, loosen the screw and your floor will move.
When your floor moves your grout cracks. When your grout cracks your tile may become loose. When your tile becomes loose your tile may crack. When your tile cracks your dog will burst into flames – again. Put thinset beneath your backerboard. And put your dog out.
Installing thinset beneath backerboards
Once you have the area fully covered with thinset you can lay your backerboards into the bed of thinset and screw it down. DO NOT use drywall screws! Let me repeat that – THAT! Drywall screws are not made, nor are they sturdy enough for your flooring. You will either bust the heads of the screws off or be unable to countersink them into the backerboard. Hard to get a tile to lay flat over the head of a screw.
There are screws made specifically for cement backerboards. You should be able to find them at any hardware or big box store. They have grooves on the underside of the head which will dig into the backerboard and create its own ‘hole’ in which to countersink the head as it is screwed in. How cool is that? If you look closely at the photo you can see the ‘grooves’ beneath the head. They are more expensive than drywall screws – just so you know. But you need to use them.
Each manufacturer has their own specific spacing instructions for screwing down the backerboards – follow them – really. Some say every 12″ and some want every 6 – 8 inches. The board you use will determine the spacing. (And its right there on the sticker so don’t tell me you couldn’t find it.)
Start your screws in the center of the board and work out. This eliminates undue stresses on the boards. If you screw all the way around the outside and it is not perfectly flat you are going to have to release that pressure somewhere and it
Backerboard screw
won’t happen until you have all that pretty tile on top of it. Working from the center out eliminates that. It would probably never, ever be a problem but if you’re anything like me your installation would be the millionth one for that one in a million occurrence.
Backerboard placed into thinset and screwed down
Your floor is probably too thick (should be) for the backer screw to actually penetrate into the floor joist. If not, or just to be safe, do not place screws into the area above the floor joists. The plywood or chipboard which makes up your floor will expand and contract at a different rate and, more than likely, in different directions than your joists. If you screw your backer into the ply and into the joist six inches over it will cause inconsistent movement – no good. Do not screw your backerboard into your joists.
After I have all my floor down I will go back and double the screws around every seam. Just put another screw between every screw along the seams. It helps me sleep better at night.
The last thing you need to do is tape your seams. Get an ‘alkali resistant’ mesh tape – similar to drywall tape – and place it over all your seams in your floor. Then mix up some thinset and trowel it over the tape with the flat side of your trowel. Just like taping and mudding drywall. This will make your floor one large monolithic structure and lock it all together. You want alkali resistant tape so it will not break down due to chemicals present in most thinsets. I do not have photos of this because I do it as I set tile.
That’s it! Congratulations, you now have a perfect floor for your perfect tile installation. When installing floor tile – or any tile for that matter – the most important aspect of the installation is always the preparation. Everything beneath your tile is important, if any one aspect is done incorrectly it may compromise the integrity of your installation. Take your time and do it correctly, you will be much happier for it.
Now go put your dog out.
can i install 20 x 20 tile tight together with very little grout or do you have to have a grout line
Hey Rick,
You need a grout line. Really. Can I install tile without a grout line?
Had a flooring guy install 12×12 porcelain tile in my kitchen this week.
It wasn’t until after he was finished that I found out he did NOT put a thinset underneath the
1/4 inch hardiebacker. I was sick about it.
Is my floor definitely doomed? After 4 days of disruption, the thought of having to do this again is hard to take.
Hi Caren,
No, it isn’t definitely doomed.
It may be fine, it may not. I can’t guarantee failure, I can only guarantee success with proper methods. I would just make sure that, should you have any problems in the next year, the contractor will take care of it. Most states require a one year workmanship warranty. If that floor is gonna have problems it’ll happen within three to six months.
Thanks Roger. I know that no one can know what will happen, but it is nice to know that there is at least some hope.
I just feel so stupid: I had my doubts about some of the installation methods and I let myself get talked into proceeding. He just seemed so confident. It is an extremely small kitchen, 8×5, so maybe that will be in my favor.
Thanks again,
Caren.
Hi Roger,
I used your website about a year ago while installing a small area of natural stone. The project was a success and I am back for more!
I think many of my questions have been answered above, but would like to receive some confirmation before beginning. I have my kitchen gutted to the studs. There is a 3/4″ plywood sub floor in good shape. I am trying very hard to keep my new tile floor level with the existing wood floor in the surrounding areas. My contractor recommended using Ditra to do so. The wood floor is 3/4″ (give or take due to sanding)… so if my math is correct the below materials should ensure a smooth transition.
My approach will be as follows:
1) Install 3/8 plywood to sub floor, keeping 1/8″ spaces between sheets and staggering them. Do not screw into floor joists.
2) Apply thinset, install Ditra.
3) Thinset over Ditra… then tile, grout, etc.
I would use something like the “Schluter®-SCHIENE” as an edgeebetween the tile and wood.
I mainly wanted to confirm the proper installation of the plywood and that Ditra is an adequate application.
Thanks!
Hey Nick,
Absolutely correct! Whaddya need me for?
You should fill those 1/8″ gaps in the plywood with silicone to prevent thinset from filling them as you install the ditra. It will maintain the integrity of the movement allowance.
Oh – that’s what you needed me for.
Thanks, I’ll let you know how it goes!
Roger,
I just read all of your insiteful comments about installing cement backerboard on a subfloor. Unfortunately, I didn’t see the answer to my problem. After removing the finished floor in my upstairs bathroom, I was shocked to see that the contractor who built the house had put down 3/4″ particle board over 3/4″ plywood. As you might imagine, the particle board was disintegrating into it’s original fo of sawdust. It took a significant amount of time to remove the particle board. I got down to the 3/4″ plywood subfloor and fortunately, it was in good condition. This brings up a couple of questions.
1 – Prior to tiling, I’m going to put down 1/4″ hardi-backerboard over thinset. Do I need to another layer of plywood before I put down the backerboard?
2- The subfloor is not level, one corner is nearly 3/4″ out of level. I intend to use a self-leveling compound to level the floor. Do I level the floor before putting down the backerboard or after?
3 – Finally, what self-leveling product would you recommend?
Thank-you very much
Clark
Hey Clark,
That shocks you? It doesn’t shock me (unfortunately).
Amazing what some builder’s think is good enough.
1. Yes, you need a minimum of 1 1/8″ plywood substrate beneath the product to which you are bonding your tile. So 1/2″ plywood.
2. If you use an SLC do not use backerboard, tile is installed directly to SLC.
3. I always use Laticrete’s Latilevel – great stuff.
Roger,
What is the purpose of the 1/2 inch plywood over 3/4 inch subflooring? I don’t see 1/2 inch ply adding or aiding in preventing floor deflection. I am have my master bath down to studs and OSB subfloor. The new plumbing starts soon so your advice on sub floor prep before hardbacker install is appreciated.
Dave
Hey Dave,
There are a couple of things that aid in your floor’s deflection rating. As a general term the word ‘stiffness’ is used when referring to the sheathing panels over the joists – ‘how stiff is your floor?’ – like that. In the case of the second layer of plywood you are referring to the panel bending stiffness (mainly of the first layer). Installing a second layer of plywood over this does not affect the stiffness of your floor assisted by the joists, it assists the stiffness of the panel beneath it.
Properly orienting, offsetting and installing a second layer significantly cuts down the amount of movement the individual panels beneath it are allowed. You are essentially halving the cantilever points in the initial layer and equaling them out with the second. It’s a whole scientific thing that is difficult to explain in a blog comment.
For more leisurely reading, should you be interested, you can start with Nielsen and Woeste Impact of plywood underlayment direction Should you fancy more on the subject just google “Nielsen and Woeste” and you’ll learn more about plywood than you ever wanted to know.
Suffice it to say that the second layer does add significantly to the overall stiffness of the floor, if not the actual deflection value – at least the overall deflection ratio. We’ve tested it in labs and everything!
Roger,
To followup on your reply to Kevin’s question, I suspect that I should silicone under the baseboard tile, rather than thinset. Do I just use a small (1/16″? 1/8″?) spacer beneath to hold the gap? Also, is it best to trowel the thinset onto the tile or the wall? Thanks!
Hey Charles,
Yes, silicone in that gap. I’ll usually leave a 1/16″ gap there using … wait for it … 1/16″ spacers.
It is better (and a hell of a lot less messy) to install the thinset to the tile then install the tile to the wall.
R–
I have a small swale (depression) in the middle of one end of a floor I’m going to lay some mosaic tile on. I’m using 1/4 ” instead of 1/2″ hardibacker because of height. The subfloor is solid, with no deflection, and the swale had to stay because of an adjacent structural issue. Anyway, I was figuring the hardibacker would bend a little to conform with the swale, but–are you suggesting that I 1)could use thinset to fill the depression, letting it dry and then screwing down to the now-flat subfloor? I’m concerned that the thinset could break up, especially on the edges, where it may be feathered a bit. Or, 2) fill the depression with thinset, and then screw the hardibacker down while the thinset is wet, figuring that things will even out that way?
btw, it’s a very old house and the slight waviness of the floors is part of its character, and doesn’t bother me.
btw also, I’ve followed you for awhile, and you are the only person on the internet that I trust!
Thanks.
Claude
Hey Claude,
Provided the thinset is placed under the backer, and there are no voids in that depression (you have so much thinset beneath there that when you place the board down and flatten it some thinset will ooze out of the edge) then no – it will not crack. The only thing that will cause cured thinset to crack is movement, not load (stepping on it without movement). Once that thinset is cured and you screw it down it will be flat and will never move.
Until the earthquake.
You can do it while the thinset is still wet, but it won’t flatten out your floor. If that doesn’t bother you then that will work as well. Either way works fine, just depends on which result you’re looking for.
I trust you too! Because you asked how to do it before you did it rather than doing it, screwing it up, then asking how you should have done it!
Well done.
Roger: Hello and back again. I completed the floor given your advice and it came out great. I am going to put up 4″ base marble moulding attached to sheetrock on the wall. What would be the best type of adhesive to use for this? This is a powder room, so moisture on the walls is less of an issue. Any particular brand to use (particularly from HD or Lowes)? Lastly, i was going to use a 3/16″ V trowel to apply the right adhesive. Is that the correct size? Thank you for your time and advice. It is very much appreciated. …Kevin
Hey Kevin,
Versabond from HD or mapei ultraflex from lowes will work just fine for you. The 3/16″ v-notch will work for that as well.
Hi Roger,
I’m planning to put 250 sq ft of 18×18 marble tile in our kitchen. The sub-floor is concrete slab that has had previous tile removed. The finish is rough, but no high spots. A “tile” guy recommended I put down an inch bed of mortar and back butter with thinset because of the size of the tile. If that’s true, it doesn’t sound like a DIY project anymore. What do you recommend?
Hey Dan,
That’s one option – as long as by inch bed of mortar he means an inch thick bed of deck mud as a base substrate. If he means an inch bed of thinset or medium-bed mortar – then tile – show him the door in short order!
Being concrete you really should have a membrane or substrate of some sort over the concrete. You should backbutter the tile but ditra would be a better option and still keep it a DIY-friendly project.
Yup, he’s referring to deck mud. The tile are 1/2″ thick, plus the 1″ of mud = 1 1/2″ rise in the floor. There’s only an inch of clearance between the top of the dishwasher and the bottom of the counter top. Even if I take the adjustment feet off completely,I’ll only gain another 1/4″. I would rather not tile in my dishwasher in. Does mud have to be 1″ thick? What would the thickness be if using Ditra?
The dog is starting to smolder….I’ll get the hose.
The minimum thickness of a bonded mud bed is 3/4″ – any thinner than that and it will crack and defeat having the thing there at all. The average height between your tile and substrate when using ditra is 3/16″.
Hope your dog is well.
Hey Roger,
??? help
Ok, it happened just like you said. The dog is in flames and I’m not far behind.
The 2nd “tile” guy looked at my concrete slab and said ” Your floor has been there for 30+ years, It’s level and no cracks. You don’t need Ditra or a mud bed. All you need to do is put thinset going east west on the floor and north south on the tile and you’re good to go.”
Well, you could do it yourself with ditra, if you were planning to do that. Or let me know where you are and I’ll see if I know anyone around you that knows what the hell their doing. That’s about all the help I can offer from here (unless you’re in Colorado…)
I live a couple miles north of Orlando, fl.
I’m liking the DIY.
I know people down there but if you wanna do it yourself then just go get some ditra and have at it. It’s fairly straight-forward and I’m here if you need help.
Great read and great tips!
Hi Roger,
I have a 1940s home and want to tile the kitchen floor. I have removed all the old flooring and brought it back to the 1″ thick diagonal ship lap subfloor. Ideally it would be nice if the finished job had te same height as the adjacent 3/4″ hardwood. A couple of contractors I have had estimates from suggested using 3/8 plywood on top of te shiplap and then tiling directly on the plywood. This would in theory align the tile with the hardwood.
My question is: would it be better to use 1/4″ backer board on top of the shiplap instead of the plywood? Is the 1″ shiplap suitable structurally? It is quite solid now that I have put some 3000 screws threw it to secure it to the joists and remove the squeaks.
Thanks a bunch!
Hey Alex,
Yeah, one inch shiplap is more solid than anything you’ll run into that was built in the last fifty years.
1/4″ backer installed over it with thinset beneath it would be the way to go. Don’t let them tile to 3/8″ plywood!!! That’s ludicrous. 
P.S. That’s a lotta damn screws.
Roger: Just poked a bit more around your website and it looks like that I should only use thinset to set the marble on the floor. Is there a few brands you can recommend that I might be able to set from a big box home improvement store? Should I add any other agent to the thinset when mixing with water? Do I need a modified or unmodified mix? Sorry for all the questions, I just want to make sure I use the right product. Thanks. …Kevin
You need a modified thinset for marble. HD has Versabond from custom building products and lowes usually has mapei ultraflex II – either one will be just fine. Only mix it with water – nothing else needed.
Hello Roger. Thank you once again for your advice on putting the Durock onto plywood with thinset before I tile. I am going to tile the floor this weekend and wanted to get your opinion on the best way forward. The room is 6′ x 6′. I am putting down a basketweave marble tile (bound in sheets, its referred to as crema marfil I believe) that are 12″ x 12″. Fortunately given the size of the room, I will not have to cut much of the tile. I was wondering what you think best to adhere the marble tile to the Durock? Is thinset the best one or some particular type of mastic? Also, what type of trowel size should I use to put the thinset or mastic down (1/4″ x 1/4″ square notched as an example?). Lastly once the tile is fully down, I believe I would need to stay off the floor for at least 24 hours afterwards. Is that right? Anything else I should be aware of before I commence the work? Thank you. …Kevin
Hey Kevin,
You want to use a powdered modified thinset sold in 50lb. bags. Just mix it with water, use a 1/4″ x 1/4″ square-notch (that’s fine) and yes, stay off of it for a day.
Roger: Any particular brand(s) I should purchase or avoid? I would generally pick something up at Home Depot but if you think otherwise, would certainly appreciate your guidance. Should I also use an additive with the thinset? Thank you for your time and patience. …Kevin
You need a modified thinset for marble. HD has Versabond from custom building products and lowes usually has mapei ultraflex II – either one will be just fine. Only mix it with water – nothing else needed.
It doesn’t matter where you post your question – they all end up in the same place on the back of the site. If everyone only asks the question once it’s a lot easier for me to answer them all.
Roger,
OK – Green-E board is down and looks good from my amateurish standpoint. The Green-E board was easy to work with, though I’m sure some of that was due to it only being 1/4 inch. But it did cut real easy. Even little cut outs for corners and hear register vents cut out nice and easy with a carpet knife.
Onto tile – I did some preliminary layout last evening and I’m pretty comfortable how it will lay out and where I need to make my cuts. My question is, is it better to cut as you go, or lay everything out and cut ahead of time? I would think cut as you go, but then how do you deal with the cutting and not let your thin-set dry out (especially for a slow amateur)?
Also, any hints for cutting for a floor heat register vent? I’m not sure if it will be a complete rectangle out of the middle of a tile, or just large notches out of two separate tiles, but either way, any hints to cut while keeping the tile in tact?
Thanks a bunch,
Jeff
Roger,
Additional information. I am borrowing a “nice” tile saw from a friend, one of those wet table saws. Also, the tile is 17.25×17.25 porcelain tile. The straight cuts don’t bother me, it’s if I need to cut a squarish notch out, how do I cut that back part? One of those Rotozip things? I have a grinder – would that work with a masonry blade, or would that end up looking like dog droppings?
Thanks, Jeff
Rotozips work or you can flip the tile upside down, hang it off of the front of the saw table and lift it up into the blade to make that last cut. Grinder works too. It looks fine if you take your time with it.
Hey Jeff,
I prefer to cut as I go. If you pre-cut, which I still do at times, you need to make sure everything goes back in exactly where you took it out or you’ll need to make more cuts anyway. You can always just mix up smaller batches of thinset.
If you can’t get the vent cut out of the tile without them busting you can always mark the tile (make sure you mark it accurately) and install it without cutting it. After the thinset cures you can use a grinder with a tile blade on it and cut the vent out. That also works well if it’s in the middle of one tile.
Roger,
So a friend of mine said I should “back butter” or whatever to get thin-set on both the floor and tile before I put it down. I wasn’t intending to do this. I know I have bigger tile, but I figured using the 3/8″ trowel would be good as long as I make sure the tile is pushed down into the thin set well. Am I in the right mind set, or should I smear on the back too?
Also, I don’t think this will be a problem, but might be if I back butter, if the thin-set oozes up between the tile, I should wipe that away right away so I have room for the grout, right?
Thanks a bunch (as usual!)
Jeff
Hey Jeff,
Your friend is correct, with large format tiles you do need to backbutter them. It will give you a better bond and ensure a full bond into the backside of the tile. Keep your grout lines as clean as you can as you set the tile.
Just so I’m clear. When you say T&G you mean T&G plywood? Not like the old T&G diagonally laid floor bds. right? Then, the 1/2 inch is just regular plywood and not T&G?
I thought cement board was the minimum to put under tile and a plywood underlayment would just suck the moisture out of the thinset, breaking the bond. I need to do cement board if I don’t do Ditra, right? I only ask because it will mean a 2-hour trip to get the Ditra, and I’ve never used it before.
The previous plumbers cut into joists AND a header (right term?). It’s a 2nd floor bath. Then, they built a kind of superstructure on top of the old joists out of 2X4s, toenailing it to the old joists, with 2x4s running with the old joists. Don’t know how much good that did, because the original joists run past the room to the middle of the house. I’m kind of looking for bulletproof.
Sorry if I’m asking repeat questions. I have a contractor, but I’m the kind of person contractors tend to hate. I know just enough to be dangerous, and I want it done right, and or the best it can be.
Yes, t&g plywood. The 1/2″ is just regular plywood. Yes, you need either backerboard or ditra. Once you build the floor you can install thinset and lay 1/4″ backer down if you want – it’s just there as a proper bonding surface for the tile.
As long as the joists were sistered correctly (what you’ve described) they will be fine.
Well, no. It was not sistered correctly. That is the problem. The 2x4s are attached only to the top inch or two of the original 2x8s. Which appeared to have been 2x 10s hacked down with an ax. the 2x4s are toenailed at the bottom to the old joists. So that the 2×4 is 2+ inches above the old joists. they are however framed in on all 4 sides by 2x4s.
I am sorry this is going on and on. It’s difficult to describe what was done. All the original joists and the new incorrectly sistered 2x4s are notched out to accommodate the drains, which were moved from their original positions, as the room was rearranged. That means the 2 x4 sister is less than 2 inches in spots.
Without sistering the new lumber the full length of the old joists, I don’t see what good it does. It also should have been bolted, but I can see that was impossible. I’m wondering if I need to remove this menagerie and try to do better with some engineered lumber, or something stronger than plain pine 2x4s. I want to do what I can to add strength. but have concerns about adding too much weight to the compromised original joists, especially the structural beam/support which was also notched.
Thanks for your help. I know my concerns go beyond the right floor for tile. but the structure, weight, construction, etc. all concern me. We live in an area where older homes are considered “grandfathered in” – no permits, inspections, very few codes. If I don’t figure out the best way, it will be done the easiest way it can, because that’s the attitude where I live.
Again, thanks so much, really enjoy your site.
Been all over your site trying to find best place for my question….. We have a 1912 house. The bathroom was redone in the 80s. Got it gutted and now we’re down to no floor. Plumbers in 80s did some things that I think have compromised the structure, yet not sure.
My questions is, what’s the sturdiest subfloor/substrate combination? Do I go with the thickest tongue and groove plywood I can get, and then what is best? cement board or Ditra?
We want to put a heated porcelain tile floor in. We are down to the joists. No subfloor at all. The original subfloor was taken out in the old remodel and replaced with 1/2 inch (yikes) plywood.a So, we ripped that up.
You said somewhere 1 1/4 inches was standard. Is that subfloor and substrate combined? Do you ever do plywood subfloor, then cement board, then Ditra? The room is roughly 8×8.
Hi Sue,
The required, and proper, substrate from the joists would be 3/4″ tongue and groove then 1/2″ plywood screwed to that. Cement board does not add any significant structural stability, it needs to be built up and solidified with plywood above the joists. I have done cement board over that, heating element, then ditra, but that was a natural stone floor and I built it to be bullet-proof.
From the two layers of plywood you can install your heating then ditra, tile right on top of that. The minimum 1 1/8″ (I often refer to it as 1 1/4″) is your subfloor thickness beneath your tile substrate – the plywood layers.
Hi Roger,
Thanks so much for the super helpful and extensive website. I just finished installing backerboard on my bathroom floor using your article as a guide. My next step is to get the walls for tile as well. We will be tiling up to the ceiling around the bath but only up to about 45″ everywhere else (and above that we will have painted drywall). My wife would really like to have a wood look at the transition from the floor tile to the wall tile so I am looking at trying to install some kind of varnished wood baseboard. I have searched high and low for the proper way to install such a product at that floor tile to wall tile transition. Some say put tile behind the baseboard and use an adhesive to attach the baseboard. While others say to just start the tile above the baseboard while making sure to pay attention to the thickness of the baseboard versus the tile thickness (i.e., you might need a shim behind the baseboard). So what do you recommend doing?
Also, even if this wall tile is outside the shower, I should still use cement backerboard, correct?
Many thanks!
Hey Eric,
I would recommend finding a tile which looks like wood and putting a row of it between the floor and wall.
If you want to use actual base then I would recommend the second option – installing the wood first. Do pay attention to the thickness and be sure to leave a 1/16″ gap at the top and fill it in with silicone – do not butt the tile atop the wooden base. Your best option for that choice would be to get some plywood the same thickness as your tile, rip strips of it just a bit shorter than the base, and install it to the wall, install the base right to it. This will kick the base out at the proper depth and give you solid backing for your base.
While not necessary, backer is a better option. You can install the wainscot directly to the drywall, though.
Sounds good. Thanks, Roger.
So just to clarify, for the second option I would
1) install backerboard from the floor up to the transition from wall tile to drywall (around 45″)
2) screw in 1/4″ plywood against the backerboard at the base (slightly shorter than the baseboard height)
3) nail the baseboard against the plywood.
4) tile up above that leaving a 1/16″ gap for silicone.
Sorry for the redundancy but I’m a very step-by-step thinker. Thanks!
Yup, that’d be the best way to do it I think.
Wow…wicked fast. You rock!
Hi Roger,
I’m following up on this post like a month later, but I’m finally getting around to tiling in my bathroom. You gave some great advice (above) on using a wood baseboard. My question now, though, is do I install the floor tile before the baseboard and wall tile? I’ve seen some other sites that recommend starting with the second row of the wall tile and then doing the bottom row (or “adjustment row”) last. What would you recommend doing?
Thanks, again!
Eric
Hey Eric,
I always install the floor first. You can do it either way, though. It’s easier to do the floor, let it cure, then draw a level line one tile high for the first row and cut whatever you need right to that. Once your level base is set it’s just stacking squares from there.
The adjustment row is the same thing, you’re just adjusting to the level line rather than having to attach level ledger boards, install tile, remove the ledger boards and cut your row to the installed tile. It works, I just don’t like doing it that way. Either is completely acceptable.
Roger,
I am planning to tile the master bathroom in my modular house using 20″ x 20″ porcelain tiles over latex modified thinset over Hardiebacker board over 3/4″ OSB. The problem is that the latex modified thinset label states that it cannot be used between cement board and OSB. Which thinset can be used for this application?
Vicki
Hi Vicki,
It states that because it will not adhere long-term to the osb. Since you are not adhering the cement board to the osb (it’s only there for support) it’s not an issue. It can be used there just fine – they are referring to bonding properties.
I am going to be installing tile to a existing cement slab. I am assuming I need Kerdi as a substrate instead of the cement backer-board. what type of preparation do I need to do this right? How expensive is this Kerdi stuff?
Can I put Kerdi under pergo floors?
thank you,
Anita
Roger,
I’m trying to tile a bathroom floor with 3/8″ x 6″ x 12″ marble. From the plywood subfloor to the height of the hardwood hallway (leading into the bathroom) is 1 3/16″ depth. Installing Hardie backer (which the website indicates is .42″ thick (or about 7/16″)) with the 3/8″ tile gets me to a depth of 13/16″. This is 3/8″ short of my hallway height. I realize you apply mortar under the backer board and thinset under the tile, and I’m wondering how you account for the thickness this material adds once the backer is screwed down and the tile is ‘pressed’ into the thinset. This is an experience question, which when it comes to tiling, I just don’t have. I was planning on using a 1/4″x1/4″ square notch trowel for both mortar and thinset applications but would gladly get another trowel if it improves my chances of getting close to the hardwood height. Thanks for the help.
John
Hey John,
It’s simply a matter of volume. A 1/4″ x 1/4″ trowel will leave a minimum, and nominal, layer 1/8″ thick beneath whatever it’s under. I would use that for your backerboard. You should then get a 3/16″ x 3/16″ trowel to install your tile. You can adjust your tile as you set it with more or less thinset beneath it to get it to the proper height. While you can get fairly close with simply the size of trowel, there is always adjustment necessary and we never rely simply on trowel size for proper height. Those two trowels should get you really close to where you need to be.
Thank you!
So, how long do I have to wait to start tiling? Can I screw down my Hardeebacker, following all of your instructions, of course, and then start tiling? Or do I need to wait over night for the thinset to dry?
Thanks for your great website.
Bob S
Hey Bob,
You can begin tiling right after you install the last screw into the hardi. No need to wait.
Roger: Thank you so much for your prompt response. I certainly appreciate it and intend to do the plywood installation tomorow and will then follow-up with the Durock. Have a good Super Bowl weekend and thank you once again. …Kevin
Roger: My apologies. I prefaced my question to you as Dave. Please accept my apologies. An egregious typo on my part. Thank you. …Kevin
No worries Kevin, I’ve been called worse.
Dave:
First, I want to say this is a great forum and I appreciate the time you have afforded to so many of us in need of guidance. Thank you for your time and dedication.
I have a 6′ x 6′ powder room that I ripped out to the studs. I removed the old floor (75 years old) and laid 3/4″ CDX on top of studs that had I cisterned new 2″ x 6″s to (lag bolted through the old members) as the old framing had been chiseled in a manner that did not create a flat surface for a subfloor to lay on. Before I laid the plywood down, I put liquid nails on the edges of the 2″ x 6″‘,s that the plywood laid on. I then screwed all this into the studs using 3″ inch exterior grade screws. That is all fine and this is something that I have done that 2 times before in this home in other bathrooms that I have refinished. I certainly am not a professional, but have been told that this is adequate for the the subfloor.
I was going to lay 1/2″ plywood on top of this and anchor with 1 1/4″ exterior grade screws. Before I commence that effort, I wanted to ask the following questions:
1. I intended to screw into the 3/4″ plywood but make sure that I did not screw into the underlying framing (the 2″ x 6″‘s). Is that correct?
2. I was going to leave 1/4″ space around the perimeter of the around
3. I was going to leave 1/8″ space between any seams in the plywood field
4. I was going to more or less screw everything down about 6″ on seams and 6″ in the field
5. I was going to make sure that the plywood was staggerred so that four corners did not meet
6. Do you recommend resin or tar paper between layers to reduce squeaks?
7. Any particular grade of plywood that I need to use for this layer? Is CDX ok?
8. I did not intend to put any type of adhesive between layers. Is that correct?
9. Should I fill any of the voids on the perimeter or the field with caulk or some type of filler?
After that, I was going to use thinset on the plywood, and then lay 1/2″ Durock on top of same. I was going to use Durock screws and tape all seams in prep for marble tile (basketweave design) that will sit on top of it. I was going to follow all instructions as outlined by USG for installing the Durock unless you have other guidance.
Would you be so kind to let me know your thoughts. Thank you once again for your service. It is most appreciated.
Hi Kevin,
You have it correct. I do not use anything between the layers of plywood, and there shouldn’t be any adhesive there either. Technically you want AB grade or better for your top layer, but lower grades are used all the time so you can use the CDX, but the AB would be better. No need to fill the voids around the perimeter. Make sure you do not get thinset in them as you install the backer. USG’s instructions are in line with TCA standards. Good planning!
Roger
I have a very old house and the previous owners had put down some awful flooring. There is wood slats for subfloor somewhere down there underneath a layer of black tar adhesive, a layer of old linoleum (1920’s) and mastic (I was able to remove the top layer of linoleum). I have already tried to remove the stuff but to no avail. Now I have an unlevel surface and 130 sqft of tile to lay.
Should I try and level it out with the leveling cement and then backer board. Or, should I just thinset below the backer board and get a level surface that way?
thank you,
Hey Max,
If you use the SLC you need to use a different membrane. Screwing the backerboard through it will crack it. You can use SLC and a membrane such as ditra or just use the thinset and backer. If you do the thinset / backer method just get it in there level, let the thinset cure, then screw it down. This will keep the floor level as you screw through it.
Roger,
I already bought the backer board and the SLC. I would rather not have to buy another item like the Ditra. So I laid my backer board last night.
Thank you for your help on this one. I have a bucket of water on standby just in case my dogs start to spark.
Max