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.
I so want laminate in my kitchen but there must be a high joist in my basement. There is a high spot in the center of the room. I can’t think of anything to do other than take the sub-flooring up and planing the board in the basement ceiling. What else can I do?
Hi Sue,
You can use an slc (self leveling cement) or a patching compound to feather out the hump.
Two questions;
1-The CB edges near the wall are tapered. Do I need to fill them to make them flat before tiling? The seams were taped and filled.
2-I noticed a few dips /valleys 1/16-1/8 in CB. Do I need to fill or will thinset compensate?
Thanks for informative site.
Hi Kerry,
1. Yes, they should be filled as they are taped and mudded.
2. Thinset should compensate for that just fine.
I removed couple of my floor tiles and notice cracks in the foundation. Now I want to put the tiles back. What can I use to fill the cracks? And also the foundation has become uneven, from what I’ve read the foundation need not be level, but flat, correct? Thanks
Hi Rey,
Correct, it needs to be flat. You need a crack suppression membrane of some sort, redgard is one type. You also need a soft joint over those cracks.
If there is some give in the floor when you walk on it can real time still be used?
Hi Renee,
Real Time with Bill Maher?
Your auto-correct is an asshole.
If you mean tile then no, the deflection must be dealt with first.
Will thin set under the cement boards be sufficient?
Sufficient for what? Is that what you meant by ‘bakeries’?
Will thin set under the cement bakeries be sufficient?
Hi Renee,
I don’t understand the question.
Hi floor elf,
We are getting a kitchen subfloor ready for timing and we have an area in the middle of the room where it appears that one of the joist below is a little lower than the ones on it’s immediate sides. The dip is about a1/4″. Does this require some kind of filler before the cement board is placed down? I fear cracking. Thanks
Renée
Hi Renee,
Yes, it does. Or you can simply put more thinset there beneath your backer, level out that sheet of board, let it cure, THEN screw it down the next day. That will give you full support and a flat floor.
Hi Roger,
DIYer here and doing tile for the first time. After looking through your site and all over on the internet I think I have the tiling down, just not sure about the subfloor.
We’re planning to lay tile (18″ using ditra) through a hallway, bathroom and kitchen in the house we just bought. Most of the subfloor is 12″ wide wood planks with hardwood and then plywood that appears to be 1/4″ (currently covered with a combination of carpet in some areas and the rest linoleum/vinyl). The end of the area to be tiled is part of an addition and has plywood subloor up to the same height as the older floor.
Is the older floor adequate for tiling and is there anything special needed at the transition from the older floor to the newer one?
Thanks,
Andrew
Hi Andrew,
It sounds as if it’s adequate. If you have a total of 1 1/8″ thickness of subfloor, between the plank and ply, over the joists then that’s sufficient. Being two different substrate methods (although they are both wood) between the old and new I would likely place a soft joint over that transition.
Hi Roger, a contractor wants to charge us $600 to “level” our small bathroom floor (10×13) before installing tile and yet we know that the only section that isn’t completely flat is right in front of the sink. Is there any need to level any of it beyond that section? Thank you
Hi Dianne,
I don’t know, I can’t see your bathroom from here.
Normally you want the entire floor leveled with the same product so your tile is not being installed over two different substrates. Ask him to show you why he needs the entire floor leveled.
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.
Hi Tanya,
Tile can be installed over scarified concrete. The slc won’t stick to the urethane glue.
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?
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.
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
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.
Sorry, when I said level, I meant flat.
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.
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.
Since it was a small area, I ended up using a concrete grinder. Messy but effective.
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
Hi Robert,
You can make that up with thinset as you set the tile.
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!
)
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?
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.
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.
Correction!!! How can I make the floors LEVEL – they are flat
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.
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
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?
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
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.
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.
Hi Karen,
Yes, a mortar chisel will work. And yes, the mortar will level it out as you’ve described.
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?
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.
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
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.
Look for a 3/8″.
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
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.
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
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.
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
Hi jmd,
I’ve never seen an unflat level.
Yardsticks are cheap and flat. Your floor needs to be within 1/4″ in ten feet.
Roger, I am tiling 250 sq ft in my basement using 6″X24″ tile. What would be the most the floor could be uneven before leveling is to be involved?
Hi Mark,
It should be within 1/4″ in ten feet and no more than 1/8″ in two.