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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Tanya

Wow thanks Roger.. so if I scarify the glue off the concrete. Can tile be installed or will I need to use slc to smooth the surface.
I have been told that I have to remove the glue or the slc won’t stick to the urethane glue is this true?
so glad I didn’t rent the strip blades you have been great help.

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Martha

On a floor, is it better to put up sheetrock and tile over to it. Or is it best to tile first and bring the sheetrock down to the tile?

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Roger

Hi Martha,

Doesn’t make any difference. I put up the drywall first, but be sure to leave at least a 1/4″ gap between your tile and drywall. I actually hang the drywall about 1/2″ off the floor, then install the tile flush with it. That leaves a 1/2″ perimeter gap for your tile installation.

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Tanya

Hi Roger
I just removed buckled hardwood floors that were glued down directly to concrete, hot water to loosen wood and crowbar.. hard work. I had an plumbing leak it’s fixed now. Well the super strong wood glue is stuck to concrete major amounts you can see the trowel marks in glue. I tried scraping it doesn’t want to come up easy. I think it would take me a month scraping by hand. can I just cover my slab with self leveling compound. Or would a edco with strip certs blade get it off? slab is flat but concrete is dark and rough 1970 house so it’s not pretty. Thanks for any advice
I want to install porcelain wood planks

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Roger

Hi Tanya,

You can install slc, or you can use a grinder with a scarifying wheel on it to remove it. I don’t think the blade would actually do much, probably be more trouble than help.

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Pam

Sorry, when I said level, I meant flat.

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Pam

I have removed vinyl flooring from a 35sq/ft bathroom. The concrete floor is level except for one small area between the toilet flange and the sink cabinet. It is 1/8″ higher than the rest of the floor. Do I have to level the whole floor or will the mortar make up for this difference? I am laying 18×18 marble tiles with a 1/2″ trowel.

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Roger

Hi Pam,

You can make up for that with the mortar, just make sure you begin setting tile at the highest point (or at least ensure you KNOW how high that is as you set the rest) so you don’t get to that point and need the tile higher than what you’ve already set.

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Robert

Hi Roger,
I have a small tiling project, 5’x5′ in a bathroom. I am using 12″ porcelain polished tile and want to install on a diagonal. My new sub-flooring are two exterior 3/4″ slabs of plywood, with the first screwed to the floor joists, every 6″and the next screwed to the first, again every 6″! The floor is mostly level but has a dip of 1/8″in one area by the wall and doorway!
Can I make up that dip with extra thin-set to keep a flat tile look or do I need to (slc) to make up the difference?
Thank you in advance!!
Robert

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Roger

Hi Robert,

You can make that up with thinset as you set the tile.

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Daylyn

We are DIY-ing our floor tiles now. The level showed the floor is level when we started, but as we are installing the tiles, we found that we are using more and more cement to make the tiles finish with a perfect level. (We were worried that if we just follow the existing floor level, we will have to cut the baseboard corners in angles when we put it back afterwards, or the ball rolls to one side of the house when we play fetch with the dog etc…)

Do you have any suggestion on how to level the floor now, beside putting more and more cement under each tiles like we are doing now? We are reducing the amount of cement each row now because we don’t want super thick floor at the other side + it has taken a lot of time! :cry: )

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Jenny Drumm

We are having the same problem right now!
We have some area’s with 1/8 -1/4″ of mortar! It’s getting ridiculous.
What did you guys end up doing?

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Roger

Hi Jenny,

I’m not sure what they ended up doing, but it is always much easier to level a floor (if that’s what you need) before you begin setting tiles. Forgoing that, just use a larger trowel to give you the needed thinset beneath your tile as you go along.

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Michelle

Hello,
I have a sea(3,200sq/ft) of 20X20 shiney floor tiles that I would like to get rid of & replace with ceramic wood looking tiles (I found a line that makes a mix of long/short w/hand scrapped appearance). The existing sea of floor tiles are in good condition, no broken, cracked or lifting tiles. When you walk across them there is a solid sound (no hollowness). Here’s is the problem…they are FLAT but not level (UGH!)! How can I make the floors flat…leveling cement is expensive…I have heard of using glued down sheets of plywood…
Can I have the existing tiles prepped with acid to remove the shine and have tile installed over them? I have talked with several installers, and the consensus is always split…if they are prepped properly shouldn’t the new tiles be fine? My friend ripped her tiles out, new installation of tiles & hers are separating from the floor….so it seems that it’s a 50-50 chance of good install v. poor install.
Thank you!!!
Michelle
background – house is in south florida, barrier island (sand), original home is built on pilings w/the addition on slab that I had secured with pilings 4 years ago.

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Michelle

Correction!!! How can I make the floors LEVEL – they are flat

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Roger

Hi Michelle,

If you want it level then slc is about the only choice short of hiring a pro to mud it. That is placing and forming deck mud over the existing substrate. This will add a MINIMUM of 3/4″ to the height of your floor.

I do not go over existing tile, but it can be done just fine provided the existing tiles are properly prepared and a proper thinset is used.

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KP

Hi Roger,
I finally found a contractor that prepared a correct subfloor in a hallway, but
the threshold into a dinning room wood floor doesn’t meet evenly with the
subfloor. We have 1/4 to 1/2″ difference end to end on about a 5′ opening. How can this be corrected? They’re just starting to lay tile &trying to figure out what to do without removing some of the wood floor. HELP PLEASE
Kathy

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Roger

Hi KP,

That needs to be leveled so there is a flat plane from room to room. That may entail slc or something else, depending on the tile substrate being used. What are they bonding the tile to?

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Jennifer

Hi Roger,

We’re tiling a 12×24 room with 12″ porcelain tiles. The floor is tongue and groove OSB. The room is built on many sonotubes and as such has some potential for movement. The floor has a high spot that could create some “lippage”. Would you recommend ditra or Cement board and any thoughts on how to address the high points at the tongue and groove junction? (maybe a planer or sanding).

Thanks so much!
Jennifer

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Roger

Hi Jennifer,

You need to place another layer of plywood over the existing osb, offsetting the seams. Then I would use ditra, although properly installed cement board will work as well. The offset layer of plywood, plus the mebrane or backer, will adequately compensate for any movement.

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Karen

I have a ~15 sqft entryway that I would like to tile, but it looks like it was tiled previously before being pulled up and replaced with carpet. There’s hunks of I think mortar still on the concrete, concrete is kinda cracked too. Maybe I can take some sort of mortar chisel to get most of it off, but I doubt it will ever be smooth. Will this be a problem for lippage? Will the morter flatten things, like being thinner where there’s bumps of mortar still, and thicker where there isn’t, resulting in an even floor? I also have to do this myself apparently because it seems no one will take on such a small job.

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Roger

Hi Karen,

Yes, a mortar chisel will work. And yes, the mortar will level it out as you’ve described.

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Lynn

Hi!
I want to install tile in our hallway into the kitchen. We originally were going to do laminate but they said when the current floor is pulled up it may leave the subfloor damaged, due to the current floor being glued directly to the subfloor. They said they would have to replace part of the subfloor…will this also be an issue when laying tiles?

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Roger

Hi Lynn,

Yes, it will. You need a proper, solid substrate beneath your tile. If the subfloor is damaged when removing the existing flooring it will need to be repaired first.

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JayDee

Hola Elf
Cant describe all the horrible problems on current job, grout joints 1/2″ +, leaks in several places, mold etc.
…A previous contractor??? Replaced part of bath floor and shimmed his 5/8 ply with strips of 5/8 ply, so I am now trying to get back to orig floor that is in other half of bathroom. It has 1 by 6 with 3/4 ply over that. I am going to use HB so I need 1+1/4″ min my question is can I use sm pieces of ply I have on job? I have been adding 2/6 and 2/8 blocks to the joists anywhere that even looks questionable
Also I am installing 16″ tile and the only trowel I could locate is a 5/8 U shape. I sent the homeowner and he looked all over town, so will it work? Thanx Elf, ur a character :lol: :lol:

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Roger

Hi JayDee,

Yes, you can use the small pieces of ply. Just ensure that you use thinset beneath your backer and it’ll be fine. That trowel is frickin’ huge! Try the internet, I’ve heard you can buy stuff off of it. :D Look for a 3/8″.

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Alec

Hi Roger,
I’m about to install about 1000 Sq.Ft. 6×24 porcelain tile with a wood look, it’s going in the basement with cement floor. There are expansion cuts all over the cement floor.
1. Do I fill them all, what do I use?
2. I’m planning on using flexbond polymer-modified mortar, is that right?
3. Will I experience crack later on in the tile? How do I prevent the cracking?
4. With this specific tile, what trowel size do you recommend?

Thank you in advance

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Roger

Hi Alec,

The search box in the upper right corner will lead you to every answer you seek.

1. No, you don’t fill them. You can use a membrane over them to be able to relocate your soft joint, but you don’t fill them, they are there for a reason.
2. Yes, that is one right answer. It’s a good thinset.
3. Not if you properly prepare and install your tile, with soft joints and perimeter joints.
4. Whichever gives you the proper coverage.

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Alec

Roger,
Can you just tell me how to used that membrane and which one should I use. I can’t find it in your search box

Thank you
Alec

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Roger

Hi Alec,

Which particular membrane would that be? Ditra? If so it just goes down on the substrate with thinset, then the tile is installed over it. It’s super easy.

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jmd

Greetings. I have a 30sq ft powder room i will be tiling. I used my 4 ft level to check for flatness, but i have no idea if the surface of the level is flat. Do you have any recommendations on an inexpensive straight edge? Also what is the tolerance for flatness. I have 23/32 osb that will be covered by 11/32 ply, covered by schluter ditra covered by 30cm x 60cm porcelein tile. Great site.
Thanks

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Roger

Hi jmd,

I’ve never seen an unflat level. :D Yardsticks are cheap and flat. Your floor needs to be within 1/4″ in ten feet.

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