Does my Floor have to be Level to Install Tile?

by Roger

Before installing tile on your floor you must make sure your floor is properly prepared.  A properly prepared floor does not have to be level. It must, however, be flat.

The only time the levelness (is that a word?) must be taken into consideration is when drainage is an issue, such as on a porch or in a shower. In those cases you must make sure your floor is not level – it has to be angled toward a drainage area.

If your floor will not be subjected to water regularly, such as a kitchen or bathroom floor, it does not necessarily have to be level. That does not mean you can have a 45 degree angle from your door to the cabinet (although I suppose you could if you wanted), it just means if your floor is not absolutely level it will not negatively affect your tile installation.

One of the things you must make sure of, among other things, is that your floor is flat. If it is not it will be difficult to set your tiles without what we call “lippage”. That’s a ridiculous word, isn’t it? Lippage simply describes the difference in the height of two adjacent tiles. If you have a tile that sticks up higher than the tile next to it you have lippage. You don’t want that. Starting with a flat floor helps prevent it.

When prepping your floor for tile trade your level for a straight edge. Don’t be concerned with how level your floor is, be concerned with how flat it is.

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Hi Roger,

Thanks for setting me straight with my grout question. This is my second question about the porch floor I am installing with the mosaic. I attached the photo to remind you what it looks like. As I said in my earlier grout question, I am tiling a floor where the center of the room will have a decorative rectangular mosaic piece. That piece will be framed with border tiles. The rest of the floor will be ceramic tile. My problem is that the mosaic will be thinner than field tiles, perhaps by 1/8″ and it is possible that, depending on tile choice, the border tiles may be slightly thinner than the field tiles but thicker than the mosaic. I am wondering what is the best way to handle this.
I considered just using a heavier layer of thinset but this is a real mosaic and I am concerned about the thinset coming up through the small mosaic tiles and screwing up my grouting. Also, I don’t want to have to mess around with pulling up the mosaic because I used too much or not enough thinset to get the right height. That would be a mess! I’m thinking that if the border tiles are a little thinner than the field tiles then that’s where I would just use heavier thinset. But what do you recommend for the mosaic? I read the post about using Ditka as a backer but I think that would raise the mosaic too much.

One thing I thought of is, before putting the cementboard down, I would put down a spacer for the mosaic that is just thick enough to bring it up to the proper finish level. When I installed the cement board, the surface would be uneven but when the tiles were installed they would all be at the same level. A possible problem I see is that the cement board joints would align with the joints between the different tile types. Is this an issue?


Erick Richards

Where can I get medium (not thin) unmodified mortar? I may need to put down about 6/8s of mortar on my floor to make the bathroom tile level over ditra. Any suggestions would be appreciated.


Paul Radvansky


I am building a new walk in shower and created a rubber membrane underneath my concrete base. Then i noticed that the pitch was not good in some spots and I added about 1/8 inch of floor leveler on top concrete. Is this okay or do I have to remove it some way?



Hi Paul,

It’s fine.


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