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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Jes

What is the best method to obtain a flat plywood underlayment for ditra XL? Subfloor is 5/8″ with high and low spots 3/8 -1/2″ max, joist 12″ oc. SLC to fill up the low spots followed by 1/2″ plywood? I’m concern of screws cracking the SLC. Will this create a problem? I like to glue some “furring strip” cutout matching profiles of the low spots for the screw and use SLC around the furring strips beneath the 1/2 ” plywood? thanks for your help

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Arthur

I replaced a small portion of my wood subfloor in my kitchen, now the piece I replaced is about a 32nd of an inches higher on a portion of the seam. will it make a difference if I lay the vct tile over it.

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Ken

How flat is flat enough. I have a large room – 12×24 and I have a concrete slab floor. Took off the carpet. What kind of variance over what length can be tolerated when using tile (36×6 faux wood porcelain) and or engineered hardwood (haven’t decided which I am going to use)

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Roger

Hi Ken,

Allowable variance is 1/4″ in ten feet and no more than 1/8″ in any two foot span.

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Orlando Solorio

Hey Roger question. I am tiling on a concrete sub floor but there is a lot of glue from what I believe was hardwood flooring or laminate. I have attached an image. So question is do I have to scrape all that glue off? Or can I just install over it.

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Roger

Hi Orlando,

You want to get as much as humanly possible off of there. You can scrape (try soaking it in water first, makes it easier) or grind it off, if need be. Thinset will NOT bond to that, so you want your slab as clean as possible.

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Ana

Hi Roger. I am wanting to have tile that looks like wood installed over my existing tile and carry it over into the bedroom. However the bedroom has always had carpet therefore there is about 1/2″ transition. Can you tell me if this can be done and how? Thank you.

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Roger

Hi Ana,

You can install 1/2″ durock in the bedroom everywhere the carpet is. Or, better yet, remove the existing tile. :D

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Jared Duplantis

Hi, I’m wanting to lay ceramic tile from my kitchen into my living room however. The cement slab where the kitchen and living room meet are different hieghts. About 3/8″ to 1/2″ difference. The living room was an add on so the slab wasn’t poured at the same time. What can I do? Also, considering staining the living room maybe. Thanks :censored:

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Nate

I have a bathroom floor in a basement we are finishing. The floor concrete and we have poured self-leveler over it to deal with a small peak at a seam. Can I tile directly over the self leveler, or do I need to put something like DITRA down over the self-leveler first? (The room is 5×7)

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Roger

Hi Nate,

You can tile directly to the slc.

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Rick

What is the best method to obtain a flat subfloor. The subfloor is 5/8″ plywood and there are a couple low spots, about 1/8″ to 1/4″ max. I believe the knuckleheads who built the house put a couple joists crown down. Shingles and roof felt followed by 3/8″ plywood followed by 1/4″ durock; or 3/8″ plywood followed by 1/4″ durock and then the low spots filled in with SLC? Thanks for your help.

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Roger

Hi Rick,

No shingles or roofing felt. The ply, durock with slc over it (thinset beneath the durock) will work just fine.

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Kathleen A Ferraro

The contractor who replaced the tile in our bathroom after it was damaged by water and chemicals used to put out a fire wrote in his insurance proposal that they would remove and replace 1/2 inch cement board and 3/4 inch BC plywood. The bathroom had been installed in 2002, and we had had no problems with the tile or grout until the fire. The height difference between the tile floor and the wood floor in the bedroom was less than 1/4 inch. We indicated we wanted it to be restored to its pre-fire condition.

The new floor is about an inch higher than the original one. The contractor cut the bottom of the door to fit. The door is now 3/4 inch shorter and there is barely 1/4 inch between the bottom of the door and the floor. In addition the floor feels kind of lumpy underfoot. I am also concerned that the height difference might create problems with our curbless shower.

The wall tile job is also terrible. I have not paid the contractor’s final payment and don’t plan to. My guess is the contractor did not replace the old cement board and plywood before installing the new floor, but could something else have caused the height difference? I can send photos.

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Roger

Hi Kathleen,

I think you’re probably correct. That’s a huge height difference. He likely just went right over what was already there.

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Kathleen A Ferraro

Thanks, Roger. A floor inspector came today and was able to look below the new plywood and found it had been installed over the old subfloor. The contract says remove and replace subfloor, so I believe this is a breach. The inspector also said the floor is moving and has bumps in it. I am waiting for his report on the floor and the wall tile and plan to send the contractor a letter saying I will not pay until he fixes the problems with the floor and also the poor workmanship with the wall.

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angel barros

Hi, First I want to congratulate you for keeping this page, it helps a lot to installers like me.
I have a project of 4500 sf on a second floor. the substrate its a lightweight concrete over wood beams, and needs a lot of prep. i’m planing on patching cracks and then self leveling the floor and install a ditra underlayment and then lay tile with 12″x24″
My questions is, if the lightweight concrete its going to support the weigh of the tile, I’m worrying about doing a good installation that can fails in a year with a bunch o crack tiles or worst.

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Roger

Hi Angel,

If you are talking about gypcrete – yes, it’ll support it just fine. Be sure to use the primer for the slc to ensure a proper bond to the gypcrete.

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Albert

I live on the second floor in a condominium. I am replacing the marble tiles with 24″X24″ rectified polished Porcelain tiles. The existing area has plywood sub floor with 3/4” concrete over. I am tiling the foyer, kitchen and the powder room. The floor slopes down from the entry door toward the kitchen of about 1”. I am confused of how to tile the area with the existing condition. Does my floor have to be level to install tile? Some installers have suggested to remove the concrete and use Hardie Backboard for tiling. Others have different way of leveling the area which is to use paper on plywood, pour cement mortar and thinset and then tiles. I am really confused. What is the correct way of handling this project? I appreciate your help?

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Roger

Hi Albert,

The best solution is self-leveling cement. I highly doubt it’s actual concrete, it’s likely gypcrete (lightweight concrete). Your floor does not need to be level, but it does need to be flat.

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