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 cementious 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 cementious 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.
{ 5 comments… read them below or add one }
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.