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

If you would like to receive little bite-sized pieces of my wealth of useless tile wisdom sign up for TileTips. You will receive a short (it’s short – I hate long emails) little email with tips, tricks and secrets (and bad humor) all wrapped up in one shiny little package. You will get one or two a week (depending on my drinking schedule) and they will help you set tile like a pro. Or, if you’re a pro, they’ll make your job sooooooo much easier – and make you rich and famous. 8)

Previous post:

Next post:


I’ve searched your website and haven’t found the answer to this question. Is there a preferred direction (technical, not aesthetic) when laying 12×24 rectangular porcelain floor tile in relation to the floor joists (assuming properly prepared sub floor and base)? Should these tiles be laid with the long edge perpendicular to the joists or parallel? Thank you again for your help!



Finally someone who uses the words “straight-edge” not “spirit level”! I read a few “how to lay tiles” articles and watched videos and they all said “use your spirit level” I was pretty sure the really meant straight edge but they never explained what they meant. I kept having visions of novice’s actually using it as a level and by the time they finished the tile adhesive was about three inches thick on the other side of the room. I admit I did struggle with leveling 6 inch quarry tiles.



Yeah, Kev…I’m finding myself in that “novice” category problem. I’m tiling a 20′ by 20′ room using 6″ x 36″ tile. I started in the middle of the room, and I have approximately 4-5 feet more to go on one side and my thin set is at 3/4″. I started with 1/2″ trowel. I used my 6′ level and everything looks good, but I’m having to increase my thin set. I’m getting a bit concerned. Luckily, this is a three season room, so I have plenty of door clearance. Looking at the overall job, it’s looking nice- just getting concerned (and found your “spot on” comment). Do you have any suggestions? Should I start gradually decreasing the thinset? Thanks in advance. Anyone else with suggestions, please feel free with advice. Large area- with big concern. Please help.



Hi Bry, sorry, I’m strictly a novice myself, I just kept seeing this crap about “spirit levels” and thinking someone’s going to come a cropper one day. If I was in your shoes and it was too late to start again I’d go with what you said and try reducing the thickness as you continue. You’ll probably be the only one who ever notices any discrepancy.



Huge fan, and glad to have found your site. Quick question or two, I’ll be using a speedset mortar to set a two-tile pattern in an entryway (6×6 & 1×1 inch tiles). This thinset specifies light traffic after six hours, groutable in two. If the material does takes six hours to develop enough strength to withstand foot-traffic, why am I not concerned with my body weight on the tiles four hours earlier to grout?
Secondly, if one were to grout prior to six hours of curing, should an installer use for ex. a board to spread his/her weight over a larger area to be safe? Or is it no real concern? Much appreciated!



Hi Rick,

You should be. See, in the manufacturing world they have this magic grouting technique where they don’t put any weight on the tile at all. It’s a miracle! :D Yes, a board would work best. The biggest issue is sideways force on the tiles, sliding them out of place by sheer force, not necessarily the weight on the tile.



Ok good deal, thanks for confirming! And now that I can be confident that method will work, I won’t have to wait 6 hours 👍 (6 hours of wondering if I could have gotten away with jumping on it sooner… figuratively… … and believe me that “weightless grouting technique” had me puzzled…) To be on the safe side I feared I’d need to just assume the two-hour mark only referred to when the mortar would be “ready” for exposure to other materials (namely the water content of fresh grout) without compromising the cure- am I close on that? feel free to correct me, this is for posterity after all, but since I just couldn’t be bothered today to dig through the lit’ looking for the strength gain ratings for this material to figure it out for myself, your input is very much appreciated. And so thanks again, and also for replying quickly you’ve saved me some time!
-a fan. Figuratively



Two hours is the amount of time that compression strength will not be compromised. There is still the risk of sheer by placing lateral force on the tile (because people can’t pick up their damn feet when they walk), it takes six hours to guarantee that won’t be affected.


Leave a Comment

;) :wtf: :wink: :whistle: :twisted: :suspect: :shades: :roll: :rockon: :oops: :lol: :lol2: :lol1: :idea: :guedo: :evilb: :evil: :eek: :dance: :cry: :corn: :cool: :censored: :bonk: :arrow: :D :?: :-| :-o :-P :-D :-? :) :( :!: 8)