How to Install Absolutely Flat Floor Tile

by Roger

Absolutely flat travertine tile bathroom floorI constantly reiterate the need for a tile installation to be flat. Not necessarily level, but always flat. This is the mark of a true professional and the thing that turns an ‘okay’ installation into a spectacular installation. (Did I just type ‘spectacular? Jesus…) Anyway, the method I use on floor tile to get it flat is fairly simple and ensures that each tile is the exact same height as the tiles surrounding it.

Before I show you that you need to understand, as always, that the substrate preparation is the most important aspect of this. If your tile substrate looks like a skate park you’re never going to get a flat tile installation over the top of it. Your substrate needs to be as flat as you can possibly get it. Take time with your preparation – it makes the rest of the installation run smoothly and gives you a solid foundation.

Start by getting a few tiles set and make sure they are all flat with your straight-edge, just place the straight-edge on top of the set tiles and ensure that there are no open spaces beneath it and that every tile is the same height. You can push down on tiles that may be a bit high or take a tile up and place a little more thinset beneath it to raise it some. Once you have that correct the rest is cake, baby! (You ever seen a cake baby? They’re messy…)

All these photos are of a travertine tile bathroom floor. I used travertine photos because it happens to be one of the least dense stones and usually have quite a few pits and open spaces in the stone itself. If the tile is ‘filled’ travertine, as this is, it is normally only filled from the front so that, once installed, it has no open areas or pits on the face of the tile. You can, however, see these open areas in the back of the tile. I’m gonna show you how to fix this, too. You get a two for one with this post.

Thinset lines all combed consistently

Photo 1

Once you have the initial couple of tiles set, as in photo 1, just comb your thinset onto your substrate in a uniform direction. (Make all the little lines from the trowel go the same way) This eliminates the possibility of trapping air beneath your tile and leaving spots that are not fully adhered (hollow spots). If you make the pretty little swirlies they may look cool, but they can also trap air beneath your tile. On a side note: my spell-check just told me that ‘swirlies’ isn’t a word – so I’m makin’ it one.

In photo 2 you can see the back of the travertine tile. See how it has all those pits and crevices and empty spots? You’ll want to fill those up with thinset to give the tile a good, solid fill and, essentially, make it more dense and durable. Do this by using the flat side of your trowel (Photo 3) and scraping thinset along the back of the tile in every direction. This ensures it is completely full and there are no open areas left. (Photo 4)

Back of travertine tile - unfilled

Photo 2

Backbuttering travertine tile - filling all the spaces

Photo 3

Backbuttered travertine tile - completely filled

Photo 4

-This is what is called ‘backbuttering’ your tile. You’ll more than likely run into that term a lot when researching tile – that’s all it is. For an installation where you have an inconsistent tile or a questionable substrate you can always do this, then flip your trowel around and comb thinset on the tile as well (make pretty little lines – not swirlies!)

Now that you have a good solid piece of shiny rock to put down on your floor, flip it over and put it there. Make sure you flip it over – shiny side up. :D When you place it in the thinset on the floor place it directly against the two tiles adjacent to it (Photo 5) so that two sides of the tile are actually touching the two tiles next to it. As you do this you can push the tile down to just the right height to be flush with the tiles next to it.

Placing tile directly against adjacent tiles

Photo 5

This will ensure that the tile you just put down is the same height as the surrounding tiles. You can take your straight-edge again and use it to push the tile down and get it to the same height. If your tile goes down too far – PULL IT UP! and put a little bit more thinset beneath it.

I yelled ‘PULL IT UP’ because for some reason people think that once the tile is down – that’s it. It can’t be moved. That’s not it. Until the thinset cures – tomorrow! – that tile can be moved, pulled up, adjusted, smashed, replaced, etc. Do not be afraid to pull it back up and put more thinset beneath it if it sets too low.

Pulling back to get total coverage

Photo 6

After you get the tile at the proper height, and this needs to be along both edges that are touching, then you can go ahead and pull it away from the two tiles to create your grout line and make sure you are, indeed, at the proper height. (Photo 6)

Then just insert your spacers and make sure it is in the correct place. (Photo 7) Pulling it back also ensures that there is full coverage between the thinset and the back of your tile. Remember those little ridges that the trowel created? The ones that were not fully squished down as you were adjusting your tile will be pulled slightly as you create your grout line and this will create full coverage and support beneath your tile.

Insert spacers and you have an absolutely flat floor

Photo 7

Check with a straight edge - told you, absolutely flat

Photo 8

-You can take your straight-edge and lay it across the tile to ensure that they are all perfectly flat. (Photo 8 ) If one sets a little bit high you can simply wiggle the straight-edge back and forth until it is flush. If it sets a little too low – PULL IT UP! (damnit) and do it again.

It may seem like a tedious process – it is. But when done correctly you end up with a totally flat, professional looking tile installation which will last for years.

See: 8) Absolutely flat travertine bathroom floor tile

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Stuart Brogden

I am putting new tile in my master bath. Most of the area was carpeted, the small room with the toilet was tiled. I’ve removed the old tile and ground down the old mortar. The concrete bows up near the toilet ring, about 1/8 inch some 18 inches from the side wall.

I am using 6 x 24 plank tiles.

Should I try to grind down the old concrete, use leveling compound (how to transition through the doorway?), or handle it with thin set?

Reply

Roger

Hi Stuart,

You need to grind that down. I can’t answer the doorway question as I don’t know whether the bathroom floor is concrete as well (I assume so) or whether it is higher or lower in relation to the room with the toilet.

Reply

waaa hoo

Set some 12 x 24′s. Flat floor method worked great. Kept the lip page to within 1/4 inch +- :)

Seriously worked great even with tiles spaced 50/50 instead of the 30/70 split the tile store wanted me to set them at.

Question: At the end of the day when you have a little left over thin set, can you back butter a few tiles for the next day or should the back be wet when set?

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Roger

The back should be wet when you set it. 1/4″ lippage, huh? Not bad… :D

Reply

waaa hoo

Hey Roger,

For the fat fingered out there, I found this tool handy for dropping that last tile against a wall into place.

http://www.finehomebuilding.com/CMS/uploadedimages/Fine_Homebuilding/Articles/241/021241090-02-vinyl-siding-tools_xlg.jpg

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Greg

Hi Roger,

I am remodeling my bathroom and have prepped for a porcelain floor (3/4″ T&G subfloor with 1/4″ Hardiebacker). However, a friend has offered me this FREE beautiful Italian travertine tile (did I mention that it’s FREE).

My question is: Can I use Ditra XL over the Hardie or would I need to pull the Hardie and install an additional 1/2″ plywood. I’ve read that the XL version of the Ditra will offset the deflection issues of a single layer subfloor. I don’t want to discover that this was wrong next year by way of a crumbling floor.

Thanks,
Greg

Reply

Roger

Hi Greg,

Ideally yes, you should add 1/2″ layer of ply. XL says it will compensate, I don’t like to test claims that marketing departments make. You can install the ditra over the backer. You can also install ply over the backer, then ditra.

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curt

Roger:
I have prepped my 5/8″ plywood subfloor in my foyer with 1/2″ durock set with thinset and screwed every 8 inches. I am considering going with an 18″ polished marble tile and a 2″ or 4″ accent tile at every other joint where the four corners of the 18″ tile meet. Since this is an entryway and due to the fact that I am using a large format, stone tile, I am considering hiring a contractor. One contractor told me the fiberglass mesh at the durock joints was not necessary but he would do so if I wanted. I suspect he will put the mesh down the same day he sets the tile. I don’t think this is the proper method. This makes me think I should ask the contractor questions about how he plans to install before hiring him. What questions would you recommend I ask?

Reply

Roger

Hi Curt,

I wouldn’t ask him anything. I wouldn’t even talk to him again. If he doesn’t know that it is absolutely REQUIRED to tape and mud backer seams then I wouldn’t trust him to lay my tile. It is necessary, it’s non-negotiable. It is fine to tape and mud them as you set tile, I do it that way. But I would be leery of someone who isn’t aware of the very basics.

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LarryCombs

Roger—

We just had 2,000 square feet of porelain tile, 9″ x 36″ installed on our concrete slab that is sixty years old. I removed the old 9″x 9″ asphalt tile before the tile people started their work. The slab is flat. when the job was finished with 1/8th inch grout lines there were places everywhere that you could stub the sole of your shoe (places that were unlevel as the thickness of a credit card or more). Is this an acceptable lay?

Reply

Roger

Hi Larry,

There is an acceptable amount of lippage and it is normally around the thickness of a credit card. The acceptable amount depends on the particular tile. Ideally it should be flat, but with 9 x 36 plank tiles they are normally bowed up in the center. If they were offset by 50% then that bow is going to be enhanced. It is a specialized installation requiring steps be taken to minimize that. Large format tile should be offset by no more than 33%, which minimizes it quite a bit. In the end it is up to you whether or not it is acceptable. All I can tell you is that there are ways to get it flat.

Reply

Larry Combs

Roger—-

Thanks for that firm neutral response. I shall proceed from here!

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Warren Nevill

Hi Roger, I’m a building surveyor down here in New Zealand tasked with measuring a sample set of tiles for surface flatness and warpage. Without a laser testing bed which I dont have (or any other electronic tile testing equipment) are you able to describe an adequate method of determining the above tile distortions. Currently thinking about using a straight edge and some sort of regulated packers, maybe drill bits, callipers etc. Any thoughts would be appreciated. Thanks Warren

Reply

Roger

Hi Warren,

I would use a straight-edge (a precise one) and a micrometer. It’s about the only way you’ll get accurate readings.

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Kerry Robinson

Anything wrong with tiling first floor floor? (Not ground floor floor) been told the first floor floor won’t take the weight of tiles? Can this be an issue?

Reply

Roger

Hi Kerry,

It depends on the framing of your floor. If your joists have enough deflection ratio then yes, you can absolutely tile it.

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kevin

If I can’t tile an entire floor at once, where or how do you finish in order to be able to start tiling the next day? Once your first tiles have set, when you start the next day, you cannot make minor adjustments to have them level the new bunch of tiles…….

Reply

Roger

Hey Kevin,

If your tiles are flat and even with all the other tiles you laid that day then there is no reason you should need to adjust the ones which are cured when you begin the next day. Just make sure to scrape all the wet thinset from the substrate directly against the tile, you can just begin laying again the next day as normal.

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kevin

Great…..thanks.

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Hal

Hi Roger,
I purchased chiseled-edge travertine (Versailles pattern) for an office and need advice prior to beginning. The travertine tiles are unfilled and upon laying them out I discovered they were not cut for grout lines :twisted: which blows my thought of using a lippage system like TLS or MLS.
so I will but them together and was thinking of leaving them unfilled until the end and sealing over everything after installation.

now the questions:
1) I have scraped, sanded and mopped the slab but still have small places of primer in the pores of the concrete – do I need to chemically remove this also? If so, with any particular product?
2) when I back-butter the tiles, do I try to force any thinset into the pits/holes?
3) I have a few 16X24 tiles which are broken but fitting them together you cannot see a crack – can you do so without them separating later or should I try to place them where I can cut the broken piece off?
Where to start the pattern? I have laid it out on the floor trying to determine the pattern. I finally printed of enough diagrams to lay them out like a puzzle and determine how many tiles but where best to pick a starting point?
4) if you abandoned the pattern and placed them in a random, non-repeating pattern, does it look like $%^& but would you be able to make grout lines?
5) can I in fact seal everything post-installation?

thanks for all your help and info!

Reply

Roger

Hi Hal,

1. As long as it soaks in water when you splash some on there it’s just fine.

2. Yes if the holes do not go through to the front, if they do don’t ‘force’ it, but get it flush with the back so there is thinset in the lower portion of the hole.

3. I would use the broken ones for cuts. It will likely separate enough to be seen as the thinset cures. Chalk a line halfway along each axis so you have the center marked and start there.

4. You can still make grout lines with the pattern. One grout line will simply be half the size of the other. I normally use 1/8″ and 1/16″ grout lines when I have that issue. Your pattern may not stay EXACTLY on the line every pattern width, but you NEED grout lines in your floor. It normally looks just fine.

5. Yes.

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Jim

Hi Roger,

Installing ~6x~24 porcelain planks over concrete floor.
Big box store gave me Thin Set mix. Should use I use Medium set mix for this size tile? I do have some slight uneveness from a concrete repair.
Also was given a 1/4″w 3/8″d trowel or do i need larger? What if using medium set?
Also the tile has 1×1 raised squares on the back side. Should I back butter the tiles?
:bonk:

Reply

Jim

Update, I was able to remove the uneveness in the concrete repair with a chisel, so i am pretty even now. Another question on the planks, do you create the trowel ridges parallel to 24″ side or across the plank?

Reply

Roger

Hi Jim,

I don’t know what ‘thin set mix’ is? If it’s regular thinset then it’s just fine. Unless you have a really wonky floor then regular thinset should work fine. That trowel is also fine. Yes, back butter the tiles. Direction of trowel ridges makes no difference.

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Bill

The wife is convinced I can tile our master bath shower. I am daunted. It calls for me to cut 16″x16″ travertine tiles into subway tiles for the lower half, place an accent band, then tile to the ceiling with the 16×16. Also has two inst nooks for shampoos, etc. The walls are not even or plumb. I read the article on how to ensure an even floor. Same principles I suppose on a wall. The wall and basin are covered in Schluter. Any more suggestions?

Reply

Roger

Hi Bill,

If you already have your kerdi up then yes, using the thinset with that method is the best option. It is always easier, of course, to plumb the wall substrate first, but if you can’t do that now you can’t do it. That method works well. Best advice I can give – don’t be afraid to pull a tile off and add or subtract thinset as you need to. For some reason people think that once the tile touches the wall it’s permanent. :D

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Don

My kitchen floor is out 3/4-inch in 12-feet. Substrate is wood planks, 4-inch wide. Should I level the floor before I install the 1/4″ cement board or after? Floor is flat in the perpendicular direction. Natural stone.

The download book was very good. Thank you for your help to those who serve.

Reply

Roger

Hey Don,

It depends on what you’re leveling it with. If you’re using slc then just level it and either use a sheet membrane like ditra, you can’t install backer over slc. If you want to level it by using thinset and backer then place the thinset beneath your backer, lay the backer into it so it’s all level, let it cure first, then screw it down.

Reply

kevin

In a 3′ x 3′ shower stall, is there anything wrong with tiling the back wall completely first, and then doing the other walls after?

Reply

Roger

Hi Kevin,

Nothing wrong with that at all.

Reply

kevin

Thanks for the quick reply……

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Jamie

Roger,

I have another question for the “Tile Guru” should you have a second to help out a Newbie. I have now begun installing the tile in my master bath that has a open floor approximately 8 – 10 feet in the center and laying them on point. Talking to a co worker yesterday he asked if I there was arrows on the back of my tile and if I was pointing them all in the same direction. Went home and checked, sure enough I do have arrows and no I haven’t paid any attention to them. SOooo. My question to you is just how important is this? Will the tiles that I already have installed stick out like a sore thumb, if so is there a work around to make this less noticeable?
I sure hope that you some tricks up your sleeve for this as I am VERY slow at laying tile. Roughly three tiles an hour and I have 15 down so far in a “T” pattern.

Thanks again …..This is a GREAT site as well as the books you have….very informative!!

Reply

Roger

Hi Jamie,

It is only relevant to the installation if there is a discernible pattern on the face. The arrows are actually only used in the manufacturing process of the tiles.

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kenneth downing

What is the manufacturer recommendation on installing 12 x 24 timeless calacatta pearl tile.

Reply

Roger

Hi Kenneth,

I have absolutely no idea, you’d have to call the manufacturer for that.

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Andrea

Hi Roger,
So, I tried to lay a basket weave marble tile in my bathroom (1″x2″x3/8″ white pieces around 1/4″x1/4″x3/8″ black pieces pre-arranged on 1′x1′ fiberglass mats) over a suntouch mat. I had a pretty even floor after I imbedded the suntouch mat (but not perfect – there was a 1/8″ difference in some places). I bought a white mortar to go under the marble. It was rapid-set, but I was confident. BIG mistake! I couldn’t work fast enough to get the tile onto the floor. And it set so quickly that I couldn’t get the tiles off to fix the mistakes. So, I spent the next 3 weeks (okay 5 weeks) grumbling as I chiseled the tiles off the floor, cut them thinner so they were slightly less than 1/4″ thick and then resetting them individually with better mortar to try to even the floor. Ugh. It’s better, but there are still lots of places where I can feel the height difference when walking across the floor. Some height difference just between tiles and some height difference between whole sections of the floor. Nothing more than 1/8″, but still highly annoying to a perfectionist. I have a black grout, but haven’t put it down yet. I’d really love this project to just be done, but the floor and tiles are just not level. I’m debating getting a sander/polisher to take the floor down to level. If I grout first, I’m worried with sanding/polishing the grout will get ground into the tile faces and look terrible. If I sand before grouting, I worry I will just pull tiles off the floor accidentally. Also, I’m worried the stress of sanding and polishing will crack the tiles because this marble isn’t strong at 1/4″ thick. So…I don’t know how to best fix this. Any suggestions? I have already tried drinking.
Thanks much,
Andrea

Reply

Roger

If it is a polished marble you’ll never get a correct finish on it. It can be done, but it takes a professional and thousands of dollars of equipment to do it. Your best bet, if it’s driving you nuts, is to remove the ones that are bothering you and reset or replace them.

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Andrea

Okay, good to know. I might need to pull up a few more tiles then. Thanks so much for your advice!

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Amber

Hands down, the moset helpful tiling info I’ve found! Thanks on behalf of us with a ‘less than perfect substrate’…

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Amber

Seriously?! Moset?? Sorry…I meant *most* helpful…sheesh

Reply

Roger

Thanks Amber! I’ve always wanted to be the moset. Since I was just an elflet I’ve aspired to the the mostest moset around. And people always looked at me like I was crazy when I told them I always wanted to be a moset! LOOK AT ME NOW!!! :D

Reply

Jackie Mills

Yes, I would like to be added to your email list.
Thank you very much,
Jackie Mills

Reply

Roger

Hi Jackie,

Great! You’ll need to fill out your name and email on the page, though. If you want to be on the TileTips mailing list just go here: TileTips. For regular updates go here: Updates

Reply

Fran

Roger

Redoing bath with white subway tile and med. gray grout. The floor and shower floor is porcelain mosaic tile over poured concrete floor adhered with thinset. Can the thinset be used instead of grout on the floor as it is the same color, or would that pose a problem with stains or anything else ?

Reply

Roger

Hi Fran,

It can be, but it’s a pain. Thinset has lime in it to make it sticky, grout doesn’t. But it’ll work.

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Ray

I’m remodeling a 5′ x 10′ bathroom and preparing to lay 12″ x 24″ tile. Toilet and sink cabinet removed, but tub still installed. My concrete floor is not level and need to know how to best prepare for tiling. What kind of advice can you give?

Reply

Roger

Hi Ray,

The best way to level a concrete floor is with self-leveling cement, or SLC. You can find it next to the thinset at any big box store.

Reply

Ray

I removed the linoleum, how do I prepare the floor for self-leveling compound? Can I just scrape the old glue or do I need something more aggressive? Do you have a guide that explains all of this?

Reply

Roger

Scrape as much of the old glue off as you can then use the primer for the slc. After that cures just pour your slc.

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Norm

My question for you…when laying the first tile, should it be bubble level?

Reply

Roger

Hi Norm,

Sorry for the delay, been out of town at the new Schluter facility all week.

If you want a level floor then yes, it should. However, you also want a substrate that is bubble level as well, otherwise you’re building thinset to compensate in some areas and may not be leaving enough thinset beneath your tile in others.

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Gary

Hello, nice helpful spot you have here! My question is that my wife decided to change to 18″ porceline tile in our bathroom floor, and we have already put down our electric wire mats and put the ditra down. When putting the ditra down we had to place it in in 3 sections in a small bathroom and wound up with our usual divits, 2/16″ to maybe 3/16″- wave pattern in aprox 5 small 3″x 4″ to 4″x 6″ spots. Other sites say to use-Custom Building Products 50 lb. Marble and Granite Fortified Premium Mortar.? Can we just add more mortar where needed as we did in the kitchen, which turned out great./? or do I need to do something else to level the tiles? Thanks very much for your input. (sorry for the lack of spelling,but it is 3am.

Reply

Roger

Hi Gary,
If you are using the medium bed mortar like that then yes, you can add more where needed.

Reply

Gary

thanks! One other ? When I re-checked our last tile put down, last year it was 16″ tile and all we used was standard thin set from portland cement, and we have had no problem with loose or sinking tile bed, as many of your other threads had( when using tile over 12″). Is there really that much difference with using the regular thin set on tiles over 12″, or did we just get lucky,or is it because we took our time? Thanks again for your input; Gary.

Reply

Roger

Sorry for the delay, been out of town at the new Schluter facility all week.

You may have gotten lucky, and it may be just fine. The need for medium bed has a lot of factors. The flatness of the substrate and the consistency of the tile are the two biggest.

Reply

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