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.
Hey Roger,
I’ve noticed there are several choices of Laticrete modified thinset. Which one is best for above and below the Durock for 12×12″ ceramic tile in on a 1/2 bath floor?
And just in case I can’t get ahold the Laticrete modified you recommend, Lowe’s has Mapei. Again, there are several choices – Ultraflex I, II, and III. Which one of those options is best.
Hey DJ,
I prefer the 253 gold as a general purpose thinset, although the 252 silver is just fine for that application as well. If you’re stuck (
) with Mapei use the ultraflex II. Sorry, bad pun – I’m tired.
Ah ha! Thanks! I think I’ve already mentioned I’m an idiot.
Thanks a great pun.
All those choices of thinset are mind boggling. What is the Laticrete Platinum version used for? (salesman is really pushing the stuff over 253 Gold) Is the same true with Ultraflex III? Are they just adding more Latex to go from “better” to “best” versions to make them stick better (which – contrary to sticky belief – would make them worse for wet areas, if I’m reading all the info right)? Or are they more hardy to water exposure? Or, both?
I use the platinum for marble and granite. There’s more to different versions than more latex, each is designed for specific purposes. Platinum is a great mortar for natural stone a (very) large format tile. Tell the salesman that unless he’s gonna install it you’re gonna use (and pay for) what you want. That’d be like firing up the Lamborghini to run for a gallon of milk. It’ll work but it’s a bit much (not that I wouldn’t do it with the milk
).
Hi Roger
Were installing porcelain 18”x18” in our kitchen over a substrate of 3/4” + 1/2” plywood sitting on 2 x 8 joists (13 foot span). Once the substrate is installed we’ll be installing heating cables and a 1/4” coat of self-leveling cement (SLC) to encapsulate the heating cables. Do you recommend a ditra given the temperature fluctuations during heating and cooling process of heated flooring. I was advised to use a non-modified thinset when installing a ditra (both between the SLC and ditra and also between ditra and porcelain tile) as opposed to modified which takes longer to dry (non-porour membrane and tile).
We appreciate any advice or comments.
Thanks
L
Hey Linda,
I always prefer to use ditra when there will be significant temperature differences. It allows for both lateral, in-plane movement as well as vapor management. Unmodified sticks just fine to everything you’ve described – really. This is conditional on the particular type of unmodified you choose. The $5 bag of unmodified at home depot is absolute crap – you need something along the lines of Laticrete’s 317 or similar. A premium unmodified actually will create a stronger bond – I know it sounds strange but I actually spent waaaaaaaaaaay too much time researching and testing that – I’m confident in it.
Hey Roger,
This site is something else…in a good way. I’ve read a substantial part of it over the last couple days since discovering. Outstanding. Your company website also shows some very nice work.
From my early days, my skillset is mostly with framing and finish work, although I’ve dabbled in plumbing, roofing, siding, and tried to electrify myself a few times too. At any rate, we never saw much more than a bare subfloor by the time our crew was done, so my flooring wisdom sucks from every aspect of knowing tricks to knowing materials.
Anyways, I’m renovating my own place and am getting to the tile parts now. I ripped out the 80’s linoleum (sans the glue and paper backing of course), and intend to install 12″x12″ porcelain floor tiles in a 30 sq ft half bath that butts up to 3/4″ hickory hallway floor. The subfloor is weather rated 3/4″ T&G plywood screwed and glued to 2×10’s on 16″ centers. FWIW, the particular half bath in discussion is in the middle 1/3 of the joist span, about 4-5 feet from either bearing point.
I’ve done a bunch of research on substrate, and I too like to overbuild so I sleep better at night. I’m currently leaning very heavily towards traditional Durock, but you may be able to convince me performancewise on Hardiebacker, or even Ditra. Feel free to give me your sales pitch for the all options. I’m not concerned with cutting and handling like I am of performance. I love making smoke clouds with cement dust.
Despite wanting to overbuild, if I use 1/2″ backer, I’ll be above the hardwood. If I use 1/4″, I think it’ll be close, but not being experienced, I’m not sure how what thickness I’ll gain on the thinset applications.
So, if I use 1/2″ and go high, what are my options for beautifying that high edge? I noticed a pretty white bead on your company website that really popped nice, but couldn’t zoom clear enough to identify. I’ve also seen a rounded edge on similar applications, but am curious if there’s a grout joint there, how to make it look good, or what?
If I use 1/4″ is it gonna crack from deflection? Will my thinset be thick enough to get the tile even with the hardwood? Is “tile-even-with-hardwood” even a good looking goal? Or does it typically look better higher or lower? I haven’t seen enough examples to have an opinion on that. You have I’m sure.
Oh, one last thing. Should I get that glue and paper off the subfloor before laying thinset and backer? I’m pretty sure it’ll come off quick with a 50 grit belt on my sander, so whatever you say.
Thanks for your time! Enjoy your beer. Hopefully it’s Odell’s and not that flat tire stuff
P.S. The tile is 5/16″ thick with an eased edge.
P.S.S. I noticed the Durock instructions specify to apply Type 1 Organic adhesive with a 5/32″ V notch trowel, and then apply modified thinset with a 1/4″x1/4″ trowel. Really? Both? And how do I apply both at the same time without scraping the other off?
Nope – one or the other. I wouldn’t let organic adhesive (mastic) near that floor at all – use regular thinset.
Hey DJ,
Durock or hardibacker – either one will work just fine for you, as would 1/4″ rather than 1/2″. Your deflection rating is a result of your floor’s substructure – the joist system. Any backerboard you place on the floor will add no significant deflection to your current floor. It is simply there as a suitable material to stick tile to. In a flooring application 1/4″ is just as good as 1/2″ as long as it is properly bedded into thinset and screwed down correctly.
With the floor system you’ve described (I’m assuming 10 ft. joist span from your 4-5 feet from each bearing point) your current deflection is approximately L/850 which is very good for tile or natural stone. You don’t need to be concerned with anything cracking due to deflection. The only cracks that may develop would be from any voids in your layers below the tile from the T&G up – that just means get full coverage on the backer as well as tile.
Any ‘white edge’ you’ve seen on a floor of mine would actually be a Schluter edge trim. They are actually brushed aluminum color but tend to show up as white with a camera flash. You can get them in nearly any height you need to match the height of your tile. It is always best to remove as much of the old flooring as possible – it just ensures that you’re getting a full bond to every part of your floor.
Thanks very much for your time on the weekend and the info Roger. 1/4″ durock it will be, and just thinset on both sides. I’ll also strip the old linoleum glue out… Which reminds me, I also am removing the huge mirror and found that a heat gun is a preferred method to release the adhesive. In reading about other uses for heat guns I discovered I’m an idiot for not using one to rip up the linoleum. I’ve got two more baths to do, so next time I guess. The span is 14 feet (bathroom is 5 feet wide, plus wall dimensions), but there’s also another double microlam beam running beneath the rear wall of the bathroom (same direction as joists spanning steel beam to foundation wall), so it definitely feels like a stiff floor.
Oh yeah, I just realized I have another question if you don’t mind. The toilet flange is screwed on top of the T&G subfloor. I’m guessing the new sandwich of thinset-1/4″ durock-thinset-5/16″ tile will be approximately 15/16″ tall. Should I be raising the toilet flange to on top of the durock? If I can’t do that easily (since this particular toilet is all elbows to the main stack 1.5 feet away), what would be the non-leaky method of extending the flange to compensate for 15/16″ rise? My understanding is that a doubled up wax ring can’t compensate for that much heighth, but if this, and any of my other assumptions above are not true, please let me know. Thanks again.
P.S. again: I always forget something. The flange is a PVC style with a metal wring around it (built in mid 80’s), with dimensions typical of a PVC flange.
Hey DJ,
You need to get a wax extender ring. The two rings won’t work due to the plastic coupling attached (that is what I was told at one point, anyway – I’m obviously not a plumber) but you can use the extender rings which are simply a ring of wax without the plastic flange attached to it. Install the regular ring as normal and place the extender ring on top of it. They are 1″ thick so it will add that to your flange by using one.
Hi Roger,
I’ve been reading many blogs regarding how to install tile over wood floors. The advice you give seems to be the most professional, to the point, and the easiest to understand that I’ve read. Therefore, I have a few questions for you. I am installing tile in an apartment unit over a crawlspace. The floor is 2″ x 10″ joists with 1″ x 6″ planks nailed diagonally over the joists. Even though the building was built in 1937, there is virtually no deflection in the floor and if you were to jump up and down in the middle of the span, it would feel like you were jumping on a concrete slab. I am planning to install Hardibacker over the subfloor and then tile over it with 16″ x 16″ glazed porcelain tile. My questions are 1) How can I put a vapor barrier under the floor? 2) Can 1-1/4″ ring shank nails be used to attach the backer board? 3) Will using Versbond help mitigate any movement in the floor over time?
Thanks so much,
Soctt
Hey Scott,
There are a couple of different options for a vapor retarder over a crawl space installation. The easiest and cheapest would be 15# roofing felt. just roll it out and overlap your seams by at least 2″. Other options are products such as redgard which could also serve as a vapor barrier in that application. Although not normally advertised as such, ditra is designed with vapor management channels in the bottom side, so that would also be an option above your backerboard. No matter which option you choose you still need to place thinset beneath your backerboard to eliminate voids.
Technically yes, ring shanks can be used to attach backerboard. The manufacturer’s requirements trump the standards, so that would be a question answered by your specific backer. Hardie does accept ring shanks (or even galvanized nails :suspect:), I believe. They do have to penetrate the subfloor by at least 3/4″. With that said I always screw down my backers – I’m just anal like that.
Versabond does not significantly compensate for movement in your subfloor. If you are concerned about that perhaps becoming a problem at a later time now would be the time to strengthen your joist system and/or add an additional layer of plywood.
Hi Roger,
I have a question, I am installing a tile floor in a screened enclosure build on an external deck. I laid 3/4 T&G Ply getting ready to lay 1/4 hardi BB. Before I do, I am concerned about rain water getting in the screened enclosure when the storm windows are out. How should I protect the Ply? Should I put down something between the backer board and the ply? Perhaps I should just lay the backer over thin set? Should I use Redgard over the backer board after it is laid and taped? We plan on putting porcelain tile down. I’m just real worried about the rain water ruining the plywood Thanks – this is great site!!
Hey Adam,
You should lay the backer into thinset over the top of the ply. This is in no way to protect the plywood, it will however eliminate any voids between the plywood and backer. After you get the backerboard installed you can install redgard over the backer. This will waterproof the entire floor as well as give you limited crack-suppression. That’s just a big term for a membrane which helps prevent cracks or movement in your substrate from transferring through to your tile. Once you do that any water or rain getting in there won’t damage anything in your substrate.
Awesome! Thanks for the super quick response!!
Ugghhh!!! We are not very good DIY’ers! We just started to thinset the backerboard and what a mess it is! We’ve never worked with thinset before, so let me tell you what we did wrong. We mixed the whole bag at once, we couldn’t get all the lumps out, and our troweling looked nowhere near yours. Granted, we were only able to do two pieces that were about 12 inches wide and 3 feet long each before the thinset became too stiff for us to feel comfortable finishing. That’s what happens when I tell my dad not to worry about driving way down here because we can do this part ourselves.
Are you done laughing yet? My dog didn’t burst into flames, but I almost did. I didn’t expect it to be so difficult. Do you have any tips on working with thinset for the absolute novice? How do we know if we should pull up the first two pieces because it might be wrong? Off course, the second piece was around the sink pipe sticking up through the floor, so it was very difficult to use the trowel under there because we drilled holes in the hardibacker and fit it over the pipes, and my dad had done some pipe soldering so we couldn’t take the piece back off and it only lifted a few inches. I think half of that piece just has a coat of flat thinset on it.
Once you go over the thinset with the trowel, can you go back over it again? I had to restart the trowel to finish the line down, and it seemed that when I’d trowel over what I had already done, it pulled off chunks of thinset so the lines were messed up.
I’m just afraid to even try again. It seems like this should have been the easy part.
Hey Renea,
The best thing I can tell you is that it will take practice. My trowel lines look like that ’cause I’ve been makin’ ’em for nineteen years.
Just mix up about 1/4 bag at a time and mix it, let it slake (sit) for about ten minutes, then mix it again. Also mix it fairly slowly – best at around 300 rpm. This extends the pot life, or working time of the thinset.
I don’t know whether you should take those tiles up or not – I can’t see them from here.
Knock on them and see if they sound hollow or solid. If they’re solid they should be fine. If you go back over your trowel lines and they are ”chunky’ then or pulling the thinset off of the substrate in ‘rolls’ then it has likely skinned over. This is an indication that you’ve either mixed it too fast, not let it slake, or the thinset is old (thinset has a shelf life). Just mix it correctly and take your time. Don’t stress, you can always mix up more thinset. Just mix a little at a time until you get used to it.
Glad to hear the dog’s all right.
Hello Roger.
I read all through these but didnt find an asnwer to my question…so here goes. I have a 10 yeat home, 16″ 2 x 12 joists, and 3/4 plywood floor. I want to go with ceramic tile, but DONT want to go much higher due to transitions onto carpeting, etc… I have added beams under the house, supporting all the joists that support the 3/4 plywood in the tile locations…there is little deflection..I had my rather large mother in law hurl herself onto the floor (which could normally be measured in China) but other than her screaming, I could feel no deflection-
So can I proceed with what I have with Thinset, Ditra, Thinset, tile and be OK? Or is the “unsupported” 3/4 plywood between the joists too much? Thanks!
Hey Brian,
A hurling mother-in-law always trumps industry standards!
Since you’re using ceramic and not natural stone, have 2 x 12 rather than 2 x 10 and are using ditra you should be fine going right over what you have there. DO NOT let your MIL hurl herself onto the finished floor – it may crack the grout. 
Thanks for the quick reply, Roger. Sounds like good advice all the way around. I don’t know if you only give advice on floors but if I have any more questions re-modeling the bathroom, I’ll ask. Could be more Stoli in it for you.
Thanks again,
Gary
Hey Gary,
If it gets me more Stoli I’ll give you an answer whether I know it or not.
I’m glad to find this site. I need help and a little sarcasm so I know I’m in the right place. I’m replacing the floor in the bathroom of a 1979 mobile home. With 18″ spaced wood joists. There is currently 3/4 in ply wood on about half the bathroom which someone must have replaced in the past. The rest is 3/4 in particle board which is deteriorating. I’m goingto cut that out and replace with 3/4 plywood. I was thinking of adding another sheet of 1/2 in plywood over the whole thing. Do you think it’s overkill? Will I have trouble with the toilets and drains also.
I’m finishing up with Armstrong tile squares over the whole thing.
Thank you for any help you can give me. I’ve read through the site and you sound like you give good advise.
Gary
Hey Gary,
I only give good advice after a fifth of Stoli, I’m only at about 1/2 that now so you’re gettin’ mediocre advice – sorry.
It’s always best to build up an additional layer of ply on a bathroom floor, although with the Armstrong tile squares (I’m assuming the sticky ones, here
) it really doesn’t have as much to do with the floor covering as it does with simply building a sturdy floor. 3/4″ over 18″ oc leaves quite a bit of deflection under toilets and such – the more sturdy the better. Rockin’ a toilet after a long night ‘Josepe’s (Not)Authentic Mexican Food Bistro’ tends to weaken a floor. You shouldn’t have any problems with the toilet flange if you use an oversized (thicker) wax ring. Drains shouldn’t be a problem at all.
I had a dura ceramic floor installed about a year ago. Besides several other problems, I have noticed the grout pulling away from the tiles in a few places. The installer has been less than helpful, so I hired a certified floor inspector. He determined that the grout cracking or pulling away from the tiles, was from inadaquate packing of the joints and too much water in clean-up. Everything I read seems to discuss the tiles moving as the main cause. Now I find myself feeling frustrated with the findings of the inspector. The installer used the plywood or whatever, but connected it to the old tiles with a nail gun and I did not see any sticky stuff being placed between the old tiles and the backerboard. Why would the inspector think the problem was two little grout in the joints and too much water in cleanup? Could it be that there are only a few places where this problem has occurred?
Hey Sharon,
The inspector will look at an installation and give you the most reasonable, most common cause of your particular problem unless something indicates it is due to something different. Without actually tearing out some of the tile it would be difficult to determine whether or not the duraceramic was improperly installed. The most common cause of grout cracking or pulling away is movement – being that duraceramic is actually designed to move the next most common cause would be improper grout installation – that would include inadequate packing of the grout lines and excess water used in cleanup (that causes the grout to shrink excessively).
The inspector is simply telling you what he can determine within reason without actually tearing your floor apart. The fact that there are only a few places this is happening increases the likelihood of improper installation being the cause.
Hi Roger,
I’m working on tiling my kitchen and am in the positioning/cutting phase of the tiles. I’m noticing that about 5-10% of the porcelain tiles are not lying perfectly flush on the 1/4 inch backer board. Basically if I can cause the tile to lift “a hair or two” when i press on one corner.
A little background about the foundation. It was originally a linoleum floor that I pulled up to find another linoleum floor that was embossed and appeared free of voids/dips. Since it felt very rigid and flat I installed the 1/4 inch backer board (brand: Greene-board) over the embossed floor using a thin layer of mortar and many “Backer on” screws as described in your article. Unfortunately I hadn’t found your article before doing my backer board job so most of the boards are touching each other and in-line. Also the boards are touching the wall on one side, so I plan to trim 1/8 inch off near the wall with a precision tool to avoid the wall expanding problem. Additionally the backer board was really smooth on one side and a little bit rougher on the other. I installed the smooth side down thinking the tile would adhere to the rough side more, but now wondering if that’s causing the slight wobble as described in the first paragraph.
As a solution, I was thinking of sanding down the areas where the tiles aren’t lying flush, but wondering if the mortar will possibly correct those small imperfections. Or maybe I’m missing something else.
Any help with this would be greatly appreciated.
Sincerely,
Zack
Hey Zack,
Unless the floor is ridiculously out of whack (like 1/4″) there’s no need to sand it down. Use a 3/8 x 3/8″ square notch trowel to set your tile and you’ll be able to even out all the tiles. The variations may not be in your floor, it may actually be the tiles themselves. Either way you can make up the differences with thinset (mortar) as you install them.
Thanks for everything Roger! Great site.
Your very welcome, Zach. Good luck with the floor.
Roger,
Have a question I am remodeling a house built in 1957 that has a crawl space. The floor joists are 2×12 on 16″ centers with 1×8 planking on a diagonal to them. Then a layer of roofing paper as a vapor barrier. On top of that is 1/2″ plywood then they glued another layer of roofing paper to that then glued flexible tile on top. Over the years the tile was covered with carpet and in the kitchen was covered with 1/4″ plywood and linoleum. So I come along and buy the house want to install tile floor (I have done a fair share of tile before). Only problem is the roofing paper glued to the top of the plywood about the only way to get it up is take up all of the plywood about 1,000 square feet. From some of your responses thin set on the roofing paper then Hardie Board will not work.
Hey Dennis,
No need to take up all that plywood – save yourself some time.
Get it down to the top layer of plywood as much as you can and you can install thinset and hardi over the top of it. Just make sure you get plenty of thinset beneath it (you want absolute full coverage) and put a lot of screws through it. You simply want to ensure full coverage and support for your hardi.
The main problem with an installation such as this is people simply leave all the roofing paper down and go right over it without getting rid of the parts that are not secured. This leaves a void beneath the paper which thinset will not cure. As long as you try to get as much off as you can you will eliminate any of these loose areas. After that thinset and well-attached hardi will work just fine.
Hi Roger,
Started out with a pallet of Hardy board got it all leveled and flat in all the other rooms. I am down to the entry (the last 3 sheets out of the pallet). It currently has 6×6 quarry tile on a mud floor underlayment. The top of the tile is level with the plywood in the adjoining room. Question is can I strip the tile and lay thin set and 1/2′ backer which will be level with the 1/4″ backer on the plywood in the adjoining room? If not I guess will have to breakout the jackhammer again.
Thanks Dennis
Hey Dennis,
Sorry, you need to break out the jackhammer. There is not really any way to attach that backer to quarry that is likely to last long-term. I’m giving everyone bad news tonight – it isn’t just you. Sorry.
Roger,
I figured that was going to be my one option. Oh well have to do the floor in the pink bathroom also. Just do not tell the people on Save the pink bathrooms.com website. I think my neighbor may have already turned me into the pink bathroom guardians though!
Thanks for the info Dennis
One more question. Do they apply the thinset directly on the foundation (Wood planks below). They are going to put “black paper” then put thinset then backerboard. Is this correct. I know nothing and I am not sure what is correct.
Hey confused – you have a first name I can call you? Most people that end up here are confused, mostly by conflicting information.
Your vinyl flooring should be torn out before the cbu is installed. If you have planks below that vinyl a layer of plywood needs to be added to ensure solidarity. It is the same method I’ve described for your last question – F144-09. The problem is you don’t know what is below that vinyl until it is taken out. Now some contractors will install over vinyl – I’m not one of them.
The black paper (roofing felt or tar paper) is not correct. It is a method known as ‘mudding’ a floor, which is very old school, and requires a cleavage membrane beneath the floor mud to prevent the subfloor from prematurely leeching moisture from the deck mud. Backerboards are taking place of the deck mud in this instance – they’re already fully cured. The ‘black paper’ should not be installed beneath your floor!
Your floor should be in this order – assuming you have planks – from the bottom up:
Joists
plank flooring (original)
plywood layer
thinset mortar
cement backerboards
That’s it – and that is the only correct installation with those particular products. It is not a gray area – that’s it. Tell them to do it that way or find another contractor. That’s what I’d do.
I have a question. We are remodeling out kitchen and our contractor put the Hardibacker cement board on the vinyl directly without thinset. I made him rip up the hardibacker and start over with the thinset underneath the backerboard. Am I being unreasonable. They said they never use thinset under the backerboard.
Hi confused,
No, you are not being unreasonable. You are paying these contractors money, correct? Is it unreasonable to demand that the service for which you are paying be done correctly?
I don’t think so. Doesn’t really matter what he said or that he has never done it – neither indicates that his method is correct. TCNA substrate guidelines indicate that his method is incorrect. Tell him to look it up. It is method #F144-09 for installation of cementious backer units. Basically everything that I’ve written on this page in the article above – that is the correct procedure.
my tile guy installed hardi backer over a vinyl kitchen floor with screws, put an electrical heating
mat down, and covered it with thin set. next day he set the tiles with thin set and then grouted the
tile. looks and works great but….. there are now cracks running in straight lines through the tiles
but not along the grout lines. the tiles are still intact and the heating is working fine. any ideas
why the cracks are happening ?
Hi John,
Yes, I actually have a couple of ideas why the cracks are happening. You did not say it but I’m assuming here that all these cracks are running in the same direction? You also stated that the ’tiles are still intact’, I take that to mean that they are still stuck to the floor and haven’t come up, correct? You also did not state how long ago the floor was installed, I’m assuming a couple of weeks at least, nor how long after it was installed you waited before turning on the heating mat. All of these factors play a part in how stable this type of installation will be.
Let me start with what I know right off the bat was done incorrectly from what you have told me. First, the vinyl should have been removed – you don’t know what is beneath that vinyl nor how stable it actually is. Secondly; There was no thinset installed beneath the backerboard to support it, although without removing the vinyl this may not have made too much difference. Third – there is no thinset beneath the heating mat to support that area.
In three different layers beneath your tile you have areas of less than full support – open pockets which will allow the floor to move when walked upon. Every layer beneath tile needs absolute full support – even under your heating mat. Heating mats (most of them) require being ‘bedded’ in a layer of thinset when they are installed. This means thinset above and below it – to lock it into a layer which will not move.
It does not play a large part in something like this but if you didn’t wait at least 72 hours before turning on your mat the heating from the cables may have compromised the stability of the thinset before it was cured properly. Premature heat will cause the thinset to lose moisture too quickly and weaken it.
If your grout lines are not yet cracked they will be (unless your installer used epoxy grout). If he did use epoxy grout that is why your grout lines are not cracked – it’s stronger than your tile. There is movement – it’s only a matter of time before it begins to compromise your grout lines as well.
I think (this is only with the information you’ve given me and what I can assume) that the cracks are probably directly over the heating cables in your mat. Although they may run along your floor joists instead, the heating cables in the mat are areas of thicker substrate. If there is any layer below them that is not fully supported (you have three) then the cables themselves support the areas directly above them more than every other area in the floor – simply due to thickness. Everything expands when heated. When the cables are heated and they expand the combination of the cables expanding and the thinset not flexing on each side of them causes undue stress on your tile – that stress needs to go somewhere, in your case it cracked the tile.
It sounds as if your tile guy is not familiar with your specific type of installation. I have a lot of friends around the country that are tile installers that will actually install over vinyl without tearing it up but they do certain things, like screwing down through the vinyl first to ensure that there are no voids, as well as installing thinset below every layer of the floor for support. And they sometimes need to replace it because that doesn’t always work – they do that because they made that decision. The ultimate responsibility for the stability and durability of your installation falls on the professional. You hired him to do it correctly and have it last, correct? He apparently has not done that. If your floor tile is cracking it is due to improper installation – it is highly, highly unlikely that there is anything wrong with any of the products used, they were simply installed improperly.
Roger,
Thanks for your wicked fast follow-up on my last question. Ok, new one:
Replacing floor in upstairs bath, not a large one only 5′ wide. Sub-floor is currently this: 1×12(3/4″ thick) nailed to joists with 5/8″ plywood over to 1×12’s. Can I lay Ditra or 1/4″ Hardie then lay tiles?? I’m intending on putitng down 12×12 porcelain tiles. Obviously I’m considering thickness of the floor, but I don’t want to end up re-grouting everything in a couple of months. And yes I have read your points on not butting seams and taping/thinsetting seams and laying a bed of thinset over the plywood before laying tile substrate. Just a little confused on the minimum thickness of the underlayment.
And unfortunately I am one of the DIY hacks…by proxy, I have no problem asking for advice but always seem to get bad advice.lol
Thanks again-Jeff
Hey Jeff,
As long as your joists are 16″ apart or closer then yes, you can install ditra or hardi and tile. A 1 1/8″, double layer substrate is thick enough (minimum) for a tile installation with proper joist spacing. You should have that so you’re good to go.
FYI: I define a hack as someone that knows they are doing it incorrectly and does not even make an effort to get correct knowledge or figure out how it is supposed to be done properly – you are not that.
I live in a moble home. We are in the process of remodeling one of the bathrooms. The person we hired to lay the tile (claimed to be an expert) replaced all of the subflooring with 3/4″ plywood. From this point, he then began laying the ceramic tile (no backer board). Before the project is even finished, many of the tiles are breaking loose. From what I have read, installing the backer board will correct the problem of the tile breaking loose. However, I am concerned about the strength. We are modifing the bathroom due to my son and I being in electric wheelchairs. With the backerboard in place, will the tile be sturty enough to handle the wheelchairs or will they continue to break loose? Thanks!
Hi Lonny,
The problem you face (other than the fact that the tile needs a suitable substrate to prevent debonding or ‘breaking loose’) is what is known as deflection. That is basically just a measurement of how sturdy your floor is. A normal house (not a mobile home) requires not only proper joist spacing to enable the floor to be sturdy enough to support normal traffic, but also a minimum of a 1 1/4″ total height, double layer of subfloor. A normal floor requires two 3/4″ layers of plywood as well as a suitable substrate for the tile to adhere to.
Mobile homes are, by their nature, a more complicated installation. The joist structure is specified by each particular manufacturer and needs to meet a minimum of L360 for tile installation. I know these numbers don’t mean squat to you but they absolutely should to your contractor. The mere fact that he is installing tile directly to a single 3/4″ layer of plywood in a mobile home leads me to believe that he really has no idea of the scope of project he is being asked to complete.
So, to answer your questions: Yes, a suitable substrate such as backerboard will help the tiles to not break loose. However, given that it is a mobile home and the fact that the wheelchairs, which will add loads upwards of 200-300 lbs. minimum, the joist structure and subfloor beneath the backerboards need to be built to withstand this added weight. When that amount of weight is moved across the floor, the floor will need to be able to accept it without enough significant movement, or deflection, to break the tile loose.
I know it’s a pain in the ass and throws a wrench into everything but I absolutely recommend that you put a stop to the work currently being done and either make your contractor find out what needs to be done and do it correctly, or hire someone that knows what is required to install it correctly.
Roger, thank you for an informative site! I bought a small lake house and the bathroom floor needs replacing due to rotten wood from leaking toilet.
The house is on pier & beam. I plan to tear the bathroom floor down to floor joists & would like to have ceramic tile in the bathroom.
Is one layer of 3/4 plywood nailed to joists, followed by 1/2″ CDX plywood NOT nailed to joists OK for a subfloor?…followed by 1/4 cement board on top of the 1/2″ plywood?
Since I am replacing the tub, is it OK to put the tub on top of the cement board or should cement board just be placed “up to the tub”–that is put tub on top of plywood?
Thank you again for an informative website!
Jeanie
Hi Jean,
Yes, the layer of 3/4 and the 1/2″ CDX will be a suitable substrate for your ceramic. Be sure to install thinset beneath your cement board to fill any voids and ensure a solid layer for tile.
You can put the tub on top of the cement board or place the cement board up to the tub – entirely up to you. Either way is completely acceptable. If you place the tub on the plywood and put the cement board up to it be sure to leave about a 1/16″ or so gap between the tub and cement board. Many people butt it right up to the tub and eventually, due to movement of framing, joists – you know, regular stuff, the tub will move just enough against that edge of the cement board to give you a nice little squeak every time you step into the tub and it will drive you absolutely insane! (It does me, anyway
)
Thank you very much Roger! I appreciate the info!
Jean
Hi Roger,
Thanks for the great site! – has definitely been added to my favorites list. My dog urges me to follow all instructions verbatim – apparently he’s not that keen on the idea of going up in flames :).
Had 3 questions – 2 directly about tiling, and the 3’rd not-so-much, but given you’re experience thought you might have come across it..?
Its a ~50 year old home, fixer-upper, 2-story colonial-style (almost done, just the bathrooms left). Questions relate to the Master Suite, which is on the 2nd floor directly above the already remodeled kitchen). We’ve gutted the room, back to studs – was an old original (lemon-yellow tile, and leopard-skin wallpaper on top-half walls and ceiling – a real treasure) mortar/tile job (OMG what a back-breaking process that was). The original subfloor was 1/2-inch ply and what looked like tar-paper under the mesh. Completely rotted out, so cut it all away. Have sistered up various joists where either damaged, or required (putting new large soaking tub in). All Joists are 10X2 on 16-inch center. Replaced the subfloor with 3/4 inch ply to start with, and screwed it all down, now it feels nice and solid. My questions…
1. We’re installing small marble subway-tile (1/4 inch thick, 2X4 inch size, come on pre-mounted 12X12 mesh sheets) on the floor. I’m intending on following this article to the letter… [possibly further 1/4 sheet of ply – should i bother?], trowelled thinset, 1/2-inch hardibacker, then thinset and tile install. Do I need any sort of moisture barrier/plastic sheet etc? And if so, where should it go? Everywhere I’ve read, including here, it says ceramic or marble etc are NOT waterproof, and neither is the backer. The current 3/4 inch Ply subfloor is untreated. Do I have to stop any moisture from getting to the subfloor, or all the way through and into the kitchen ceiling below? (Just for clarity, im NOT talking about the shower box – Im using schluter shower system for that, with kerdi-lined shower box walls – just referring the rest of the room floor).
2. Im installing 1/2 inch green-back drywall on the walls in general. For the shower-box specifically, we’re putting Kerdi membrane on the walls, is it ok to use the same green-back drywall in rest of the room, as the shower backing behind the membrane (rather than just normal drywall as Schluter suggests?) Is the green better/worse? Membrane still stick ok? Or go hardibacker instead?
3. (and for the non-tiling question…) I was going to put the green-back on the ceiling too, but then found that for ceilings it requires closer joist-center distance than 16-inch, so opted not to, and will be forced to just put standard drywall on ceiling (1/2-inch still). Do we need to specially seal the ceiling drywall before painting? (especially above shower box?) Any ideas what with?
Sorry for the long post, and advice hugely appreciated.
Cheers.
Hey Kiwi,
1) You should have a double layer of plywood beneath your tile substrate so yes, I would use the 1/4″ additional layer (1/2″ would be better). You do not need a moisture barrier on the floor of the bathroom. The marble and grout are not waterproof but the amount of moisture it will be exposed to should be minimal and will more than likely evaporate off the surface before enough is soaked in and retained to create any damage. And if not – I wanna party at your house.
2) Green board is fine – I hate it – but it’s fine. It’s just a personal thing and I’m a stubborn, bull-headed bastard. Kerdi will stick to it just fine.
3) No real need to seal it with anything, just use a good latex-based paint and it will be fine.
Is it just me or does it seem like I typed the word ‘fine’ excessively in this reply? By the way, the walls you tore out were mud walls – I still build them when I find someone willing to pay for them. They *really* last forever! No fun to tear out, though.
Give your dog my regards.
I want to replace my tile in my entry way. The old tile is set in a cement bed and I have been advised to tear up the cement bed and then build up the floor using a sleeper floor.
My question is about the sleeper floor. How sturdy is a sleeper floor…I mean it has space between my original subfloor and “new” higher floor. I am thinking that the tiles will crack over time.
The second question is how important is it to get the strips of wood parallel and attached to the floor joists on this sleeper floor? It seems that I would be redistributing the weight of my floor if the base of my sleeper floor is not over my floor joists correctly.
Thanks for any advice you can give me
Hi Will,
I’m unsure who advised you to build a sleeper floor to tile over but that is one of the worst solutions. You’re absolutely correct, depending on the quality of wood used, the height, as well as several other factors the amount of movement makes it unsuitable for tile installation.
Your best option is likely another mud bed. Just tear out what needs to be gone and mix up some deck mud (just like a shower floor) and create yourself a nice flat, solid substrate for your floor. It’s cheaper and better and a proven method – no way to lose.
Hi Mr Floor Elf:
Love your style & humorous writing.
I don’t have too much physical strength. I love working with my hands. I’ve previously vinyl tiled & grouted the side entrance & 2 flights of stairs & now I want to tile the front foyer. I want to use granite tiles 12×12.
(I think it’s backerboard. I found it in the basement & it is grey-cement looking with mesh.)
I hope you can advise me on my flooring dilemma. But please don’t get too technical. I’m a mom of three & I’m 5.5″ & weigh 100 lbs so please nothing difficult.
The floor is now stripped down to something that looks like planks. If i’d remove those planks-I’ll fall through into the basement. Here’s the problem. If I lay down 1/4″ backerboard & the granite tile on top, I can’t open the darn door!
Any ideas??
Hiya Goldy,
They look like planks because they are planks.
And it does sound like backerboard, but I can’t see it from here so I dunno.
The problem is that with a floor installation there needs to be a minimum of support below your tile. This is measured by what is called the ‘deflection ratio’ of your floor. In English that just means a number that measures how bouncy your floor is. The higher the number the less bouncy – get it? Now, for a normal ceramic or porcelain installation this number is 360 – a number I’m fairly certain was brought about by counting the number of unicorns in a particular smurf village. That part isn’t important, what is important is that for a natural stone (granite, for instance) this number needs to be double, or 720 unicorns.
To reach this magical number requires a minimum of 1 1/2″ of subfloor – that would be your planks plus 3/4″ plywood screwed to that, then your underlayment or tile substrate, then tile. It sounds like a lot because it is a lot. You need to make absolutely certain that your floor is not bouncy below your tile. If it is your grout will crack, your tile may crack, and my dog will burst into flames. My dog is tired of bursting into flames – so don’t do that.
Your deflection number does not necessarily derive from the layers of flooring but mostly from your joist structure. As long as your joists are in good shape and you have the required number of layers in the correct order you should be fine. I can check the specific deflection ratio for you if you would like but this would require numbers from you describing your joists sizes, spacing and unsupported span. (Real tile guys actually have to know math – weird, huh?)
Cementious backerboard (the gray stuff) does not positively affect this number at all – it is not made for, nor does it help, floor deflection. So, the bottom line: You need at least 3/4″ of plywood screwed to the planks (NOT into the joists), then your underlayment, then your tile. So above your planks you need about an additional 1 3/8″ of stuff.
Now, that will get your floor to the point of being properly installed and have it last – not too difficult labor-wise, but it does require the proper layers. It doesn’t solve your door problem though, does it? If you are able to cut the bottom of the door so it will clear all these layers you can add the proper height of layers to your threshold so it is still properly sealed at the bottom and you don’t get a nice, cool breeze blowing under the bottom of your door.
The only other option would be to remove the planks in that area and drop the joists low enough to allow for those layers. But that option is not really easy – at all. So I think cutting the door down to size to allow for the tile installation would be your best bet.
Just make sure you have enough unicorns.
Thanks for dumbing it down for me. Dropping the joists is exactly the kind of physical labor I can definitely NOT do.
Don’t roll your eyes too much, but the wood which I think looks like planks measures 3/4″. (Found a broken corner where I was able to stick in a ruler.) I’m trying to keep up with your math & all the unicorns. So do I still need a 3/4″ plywood, & then the 1/4″ backerboard? & here is another eye rolling question, how can I see the joists? The floor is completely covered with the planks & they are really tight & secure. Should I pull up the planks & see what’s doing underneath?
I’m not thrilled about the idea of cutting the bottom of the door & then raising the threshold. Too much detailed surgery. I’ll need a PHD first. The door is 60 something years old & I can see daylight at the sides. Thought about replacing the whole front door. If I leave the marble saddle in place & install the new prehung door on top of the existing marble saddle, I would get another 3/8″ for clearance. It may still not be enough.
Am I completely crazy?
Hey Goldy,
Even with 3/4″ planks you need 3/4″ plywood. You do not need to use the 1/4″ backerboard, you can use something like Ditra which is only about 1/8″ thick. The purpose of the underlayment is to have a substrate suitable to stick the tile to. Backerboard, Ditra, things like that. The thickness is not important.
You can either take a look at the joists from below or take off the planks to get a look at the joists if you want to. Not really necessary unless you want an actual deflection number.
If you are going to install a new door I would pull everything out including the threshold, install the 3/4″ layer of plywood, replace your threshold and place the new door on top of the saddle at that point. That should give you enough clearance for your underlayment and tile.
Your not completely crazy… Just enough to want to install tile.
Ok, so I’ve been mulling this over the last couple of days. I work very slowly when doing repairs. I work all day, then take care of the kiddos & only after everything is done, I can treat myself & indulge in redoing the house. Now if I do the tiles in stages, like plywood one day, backerboard another day & so on.
Problem is, if I take out the front door, I can’t leave the door off for a week. I need to get the new door up the same day. I don’t know if I can finish that fast.
So now I need to get a professional to install the door & only then can I continue with the tile.
You can always pull everything out up to the threshold one day, the next day pull out the door and threshold and place 3/4″ plywood beneath the threshold, replace the door, then continue as normal. If you can pull out the threshold, place plywood beneath where it goes, then replace it all in one day you’ll be fine. The only real issue you have is that the threshold isn’t high enough. If you can get that moved up before you start you’ll be fine.
The 3/4″ plywood beneath the threshold does not have to be tied into or a part of the actual 3/4″ of plywood beneath your tile in the entryway, it can be separate. The only purpose of placing it there is to give your door enough clearance. It does not necessarily need to be installed last. As long as you can get it moved up with enough clearance before you start that would work fine as well.
You are right.
And so I did a test run. I have some interior french doors that had warped jambs- got them at a steep discount. Of course, this was b/f I started studying & experimenting as a DIY’er & I did not realize the jambs were warped. Thanks for letting me ramble here.
I figured if I can get those doors hanging properly, I’ll trust my abilities & attempt installing a front door. Well, success! The doors are hanging almost perfectly. (Can doors ever be perfect?) The reveals are pretty straight & the doors open & close smoothly. 
It took me three days, but I’m happy
So I am going ahead with the front door. Still some hurdles to cross. I really need a better math education- don’t tell my kids. I must crunch the numbers to make sure I can raise the door up enough. Not sure if I have enough clearance up on top. And the door jamb widths on the exterior pre-hungs at home depot & lowes are only about 4 & something wide. My door opening is around 8″. I know I may have to do a jamb extender.
Slow & steady here. Slow & steady.
I have a question. I was told by a contractor that PL premium and 1 1/2″ ring nails would work for installing Cement Backerboard to the sub floor????
Hey Chad,
Sure, that’ll work as long as you are installing vinyl on the backerboard. That particular method is a favorite of handymen and people inexperienced with proper tile installation. They interpret placing thinset beneath the backerboard as a way to ‘stick’ the backerboard to the substrate. It is not.
Thinset is placed below backerboards only in order to fill any voids beneath it. Any type of glue such as the PL premium you are talking about will do the complete opposite – it will leave voids and create spaces. Rather than eliminating movement it actually creates it.
Get a bag of thinset and place that below your backerboard. And find a new contractor.
Roger –
great site and beautiful work….wish you did work in CT….
I am having a full basement bathroom installed and just wanted to ask a few questions regarding tile installation.
Half of the basement is already finished. So, we will be breaking through the wall that separates the finished from the unfinished side and adding a bathroom there.
My friend is a contractor who is doing the work.
Here is the tiling plan:
Floor:
2×4 sleepers, 16 o.c. (pressure treated) attached to concrete with PL construction adhesive and Red Tapcon screws (to get the bathroom level with current finished area)
(current finished area is also 2×4 sleepers, 3/4″ plywood and carpet)
Plywood subfloor (3/4″ tongue and groove underlayment)
Plywood screwed down into sleepers
1/4″ Hardiebacker set onto plywood with thinset
Screw down Hardibacker into plywood (BUT NOT into sleepers)
Thinset
Ceramic Tile
Shower:
Swanstone shower base (bulit up on same sleepers and plywood as rest of bathroom floor)
Quikcrete Sand topping mix under Swanstone base for support (as recommended by Swanstone)
Plastic/poly sheeting for moisture barrier attached to studs with staple gun
Durrock walls
Tape Durock wall seams with fibergalss mesh tape and smoothed with thinset
Thinset
Ceramic Tile
Now here is my dilemma.
I am reading that tiling over 2×4 sleepers on concrete is a bad idea…..the only real option is a mudjob…
Apparently, moisture/dampness in the voids created by the sleepers can cause movement in the 2×4 sleepers…thereby possibly causing cracked tiles/grout. True? Any remedies for this?
Shouldn’t the combo of Tapcon screws and PL glue hold the 2×4 sleepers in place to minimize any movement?
I will try to look into the mudjob….but I have to try to find a reputable guy in my area, plus I bet it is expensive due to the labor involved….
Overall, does the plan look good? Any criticisms or suggestions would be helpful…..
If more info is needed, please let me know and I wil provide.
Thanks for the help. I sincerely apologize for the long, segmented post…I just wanted to make sure you had all the info you needed.
mm
Hey Mike,
I have combined your comments into just the one. Apparently it is too long for a normal comment box, sorry about that.
The information you’ve found is correct – you do not want to tile over sleepers on concrete. Concrete will allow moisture to evaporate up through it from the ground and this will get trapped between the sleepers. Air and moisture with no way to escape is never good for tile. Tapcon screws and PL glue are not sufficient to hold those sleepers in place when you start injecting those two things into the equation. I know that doesn’t sound right – but it is true. Trust me on that.
It sounds as if you only have about 2 1/4″ from the concrete to the level of your floor outside this area. That is actually ideal for a regular mud bed for your floor. I really don’t know the price of labor in your area for mudwork but you can always ask around. Or, if it is an option, you or your contractor can do it yourself. A mud bed for a floor is actually fairly easy if you use the correct method and take your time. If you’ve read through my ‘how to create a shower floor’ threads it is almost just like that. Same mixing ratios, same techiniques, except you are making the floor flat rather than sloping it.
The price for materials is just about identical to using the sleepers, plywood, and Hardi. In fact, it will be a bit cheaper since you are only buying concrete and sand. When done carefully (take your time) this is the best way to achieve an absolutely flat floor for a tile installation. I would do it all the time if I had the space to bring the floor heights level – you already do.
You basically just mix up the deck mud, get your height level around the perimeter and place screeds at that height for the remainder of the floor. Fill in the center and screed it off level. The next day you have a perfectly flat, level floor for your tile. If this is an option I’ll be more than happy to answer any questions you have as you go along.
The only other option I can think of to raise your concrete to the level of your floor outside that area would be a membrane made to raise the floor in commercial applications. These would be varying heights and would probably be difficult to find one that would match the height you need. They are also extremely expensive. The price of the membrane would be more than hiring a professional to install a mud deck for you.
I would go the mud bed route. It enables an uncoupling barrier between your concrete and tile and gives you a worry-free substrate. Hope that helps. If you have any more questions please feel free to ask.
thanks for the info roger .. i think i will go kerdi drain and pre slope
hello roger thanks for all the info on you site .. i have a ? can you use kerdi on the shower floor with out using the kerdi drain ? if you can how ?
Hi Ed,
You can but, to be honest, its a pain in the ass.
What you need to contend with is the weep holes in the lower half of a regular clamping drain. In a traditional shower you will have from 3/4″ to 1 1/4″ of deck mud above the weep holes. To deal with this with the Kerdi membrane you can use what we call the ‘divot method’. While more commonly used with liquid membranes it can also be utilized with Kerdi.
What you do is create the shower floor but leave a large divot from the top of the mud bed down to the weep holes. When done correctly it looks like when you made your mud bed you left a volleyball sitting on top of your drain flange. It’s a regular bed then about 4 – 6 inches around your drain it dips down in a reverse sphere to your weep holes.
The pain part comes when waterproofing this particular part of the bed. Kerdi doesn’t like circles very much. While it is absolutely possible to do it’s a questionable process for someone not very experienced with Kerdi. To ensure your floor is waterproof in that spot, which happens to be the lowest spot in your shower and therefore sees more water than any other part, you need to have a rock-solid technique and absolute confidence in your ability to properly waterproof strange shapes with Kerdi. In other words it takes a lot of practice.
After doing that you just fill in the remainder of the divot with deck mud and tile as usual. the deck mud in the divot will become saturated and drain correctly just like a traditional mud bed but the remainder of your shower will be topically waterproofed – that is waterproofed directly behind your tile – with the Kerdi.
You must use this method because if you do not have your waterproofing below the weep holes the water will drain into the top of the drain and some will drain out of the weep holes. If the Kerdi is not below the weep holes that means it drains into your floor, framing, basement, kitchen, antique pez collection, etc. It is a very specific process and one I would be extremely leery recommending to someone without much experience. Not that you couldn’t do it, just that I would not recommend it. But hey, it’s your pez collection, do what you wanna.
Another mildly insane tile contractor from New Yawk named Gueuze (pronounced goose) has put together a ‘tutorial’ of sorts describing his method of waterproofing with liquid membranes. It does, however, explain the ‘divot’ with photos and everything. It can be found Here. (The first page is with the Kerdi drain, the divot photo and discussion starts on page 3)
Hope that helps.