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.

{ 444 comments… add one }

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  • Becky

    I’m going to install ceramic tile in my bathroom, but just found asbestos tile that is loose and raising in places below well-glued vinyl. From what I’ve read about the existing tile, I need to leave it there. Should I apply leveler over the vinyl, glue the underlayment to the vinyl, or is there a better solution that I’m missing?

    • Roger

      Hi Becky,

      You can use self-leveling cement over that to encapsulate the asbestos tile. You can tile directly over the slc, or go over it with something like ditra for the tile. Do not try to glue backer to the slc or the vinyl, it won’t work.

      IF this is over a wooden subfloor, you can install thinset, then backerboard over the vinyl tile then screw it down, then install tile over that.

  • Frank

    We want to tile the basement bathroom floor. It is not level and is pitched towards the sump pump. What is the best way to get this floor flat and not level so we can keep the pitch. The SLC wouldn’t work because of the pitch. I was thinking of putting down an uncoupling membrane and building up in the valleys to find some sense of flatness. Thanks for any suggestions.

  • Marcus W Waddell

    Hi Roger,
    Question for you…I have a Jack and Jill bathroom that has a pretty unlevel floor. The floor dimensions are about 13′ by approx 5′. The first 6 or so feet is dead flat, but the last 6 or so feet the 6.5′ level touches on both ends and has a dip of about 3/16″ in the middle part. Since the floor is not level I’m afraid that SLC would flow where I don’t want it. Is a cementuous patch a better option for this? Or should I pull up the newly laid top layer of subfloor and shim it at the low spot and re-install? Will be using medium sized tiles (6×12 or 8×8 or maybe 12×12).

    • Roger

      Hi Marcus,

      That depends – what is your top layer of subfloor? If it is cement backerboard then yes, pull it back up, put thinset beneath it and lay the backerboard back down in it, get it flat and let it cure overnight, then screw it down the next morning (letting it cure keeps it flat, screwing attaches it). If it is not backerboard then a patch would be your best bet.

      What tile substrate are you using?

      • Marcus

        Thx. It’s 5/8″ plywood over 1/2″ OSB. I pulled up the plywood… Shimmied it with shingles and screwed it back down. It’s now flat. Done that in a couple of areas in the house… Worked well. Substrate will be Ditra.

        • Marcus

          Shimmed not shimmied…. Lol

          • Roger

            Yup, that’ll work just fine, even if you shimmy on it. :D

  • Stewart

    So I just came across this article and wanted to pick your brain. Putting tile in my kitchen and living room. 700 sq ft total. Starting with kitchen. I drop about 1.5″ over the 14 foot span in kitchen from energy towards kitchen sink. By my pantry it dropped about .5″ over 4′. I tried some of the slc in the pantry area but I forgot to prime. Is this a big issue? Also should I be worried about the 1.5″ over 14′?

    • Roger

      Hi Stewart,

      It may or may not be an issue. There is really no way to tell after the fact. If you have a subfloor that moves a lot then it may create problems. 1 1/2″ over 14′ is HUGE. You can tile it as long as it’s a flat slope, but it does create all types of issues with the end product unrelated to the tile itself. A rolling pin on the countertop, if they are not properly leveled, will roll off. Properly leveling cabinets over that span creates a huge issue, one end of your cabinets may be against the tile, the other may have to be 1″ in the air.

  • Barbara

    installer installed granite tile on shower walls using 1/16″ spaces horizontally and vertically almost no space at all. butted most together. What will happen. can’t grout properly. dirt and water will get in and mold and can’t be cleaned. tiles might crack or chip. I am very upset with this installation job. Also he installed granite tile to the end of the wall then pushed in sch-ulster metal trim. some metal trim is not at the edge of the wall, some tile does not meet the metal trim. spaces on the other side of the metal trim that the metal should be to the wall. looks terrible. some tile sticks out like the mortar is not level, and some time just doesn’t align correctly. shoddy job. Floor tile started in small wall where commode was. If that wall or tub area is not parallel tile will be installed at an angle to the tub. I start my tiling in the center of the room when I tile. Why do tile guys do this to people. This is so upsetting. Want to get in and out and get paid. Wants to do the floor and grout the same time without waiting for mortar to dry. So upset. Granite tile is not cheap.

    • Roger

      Hi Barbara,

      The only question I see in there is why do tile guys do this to people. Professional tile guys DO NOT do this to people. The ones who do this are not professionals. It would behoove people to thoroughly research whomever they are hiring to ensure they are truly hiring a professional. Anyone can CALL themselves a tile guy. Hopefully you have not fully paid them yet.

      BONUS: I was finally able to use the word behoove and whomever in the same sentence when answering a question. :D

  • Steve B

    Hello Floorelf… am curious about best practice for handling a bathroom outside wall edges. We are using 12×12″ tiles and a 3″ top bullnose tile (and no 2-sided bullnose available). Am thinking a mitered edge? Thanks!

    • Roger

      Hi Steve,

      Yes, a 45 degree miter on those corners works best. What I do is offset my bullnose by 50% of the tile, so place the bullnose halfway along the side of the tile and mark the outside edge of the tile on your bullnose, this becomes the inside of the miter. Once mitered your bullnose piece should be about 9 inches from the point of the miter to the end of the bullnose. If you do this each subsequent bullnose piece will be consistently offset by half a tile.

  • Gregory Carter

    I’m a homeowner trying to find out if I poured this mortar bed good enough for tile.

    The slopes are good from each angle to the drain, however there are some small bumps and valleys. How much of an issue is this going to be for me? I bought marble hex pattern that are about 2-3″ across each in a square foot sheet. I still plan on using red guard over the bed before laying the tile but wanted to know of I can compensate for those valleys with thin set or should I do something else.


    • Roger

      Hi Gregory,

      You can float out those valleys with thinset before you redgard it. You can sand down any peaks. Do all this before the redgard, then waterproof over everything. With tile that small you really don’t want any slope inconsistencies and it will be difficult to build anything up with thinset without making a hell of a mess.

  • Woodie

    My bath is 5’ wide and I noticed in the middle there is about 1/4” low area. This is a remodel it has 1×6 sub floor I put down 1/4 sheeting and now gonna lay 1/2 backer board. Will the mortar bed below the backer board correct this?

    • Roger

      Hi Woodie,

      Yes, it will correct it, but you’ll need to lay the backer down into the wet thinset and let it cure first, then screw it down. If you try to screw it down while the mortar is wet it will pull the backer down to follow the subfloor. If you let it cure first it’ll stay flush.

  • Matt

    Very much appreciate the website!! See pictures attached….I’ll try to make the question simple – I am the homeowner. How far do you go to try to get the tile plane “flat”? Have had a couple contractors take a crack at the sub floors and now its my turn. Pictures show Foyer into Hallway into Mudroom, and then down the Hallway with Mudroom on left and Foyer on right. Very high traffic area from garage and from the front door. I removed the old tile and subfloor in the Foyer and need to add material back to that area (you can see my small slab of 1/2″ OSB). Mudroom had the same thing done a while back, I believe 5/8″ OSB. The Hallway was leveled with floor leveling compound. That gentleman did a decent job with what was occurring there. The floor joists in the basement are sound, but likely are spanning a bit on the high side and have settled a bit. Long story short, there is a good dip in the Mudroom, then the Hallway sits ok, and then the Foyer, if I add 5/8″ OSB I get close in most spots to the Mudroom. Mudroom along the walls lasers at 51. Dip in the middle of the Mudroom at 51 1/2!. Hallway back to 51 1/8, and then the Foyer has some areas at 51 and some along one wall at 51 1/8. The OSB in the Mudroom is glued down. Previous contractor did not hit one joist in the basement with his screws. I have taken those all out and I’m at the point of wondering if I should tear the rest of that out and the Hallway too and get back down to the 1/2″ subfloor or tear it all the way out to the joists or just the Mudroom only or try to screw it all back down, add the OSB in the Foyer and use a leveling compound??? I’m not afraid of the work, but I also realize it won’t be perfect. Just want a sound floor and a flat plane for my tile guy!!! Thoughts? I could send you a drawing of the space with laser measurements if you need it!!! Thanks and my apologies for the book. Happy Friday!

    • Roger

      Hi Matt,

      There is a size limit on the uploaded photos – likely why they didn’t upload. It sounds like you have a LOT going on. It also sounds like something that will require someone who knows how to assess it (in person) to come up with the best game plan. You can send photos to and I can take a look. But my suggestions will likely be generalizations from what I see, it’s a difficult thing to do with just photos.

  • Dan

    My bathroom floor falls about 1/2 inch on one side. The subfloor is two 5/8 inch plywood panels thick secured over 2 x 10 inch joists, 16 on center. Approximately 110 square feet of tiled floor. I plan on using 18 inch tile over Ditra. I would prefer to level the floor. What process would you recommend?

    • Roger

      Hi Dan,

      A good self-leveling cement would fix that right up for you. I prefer customs brand slc available at HD. But any good brand name works well.

  • AR


    I have a bit of a difficult question for you (in my opinion!). I’m about to tile a bathroom (90+ years old). The floor slopes approximately 2 inches over an 8 foot length. The possibility of levelling is impossible because of a door on the low side that would cause a drastic transition. Thus the plan is to create a flat surface for the tile.

    This brings me to my actual question. The original hex tile was laid in a wet mortar bed ~3″ thick and I plan to tile overtop of the tile (this wont raise the floor a substantial amount and therefore wont mess with the radiator and toilet flange heights). Is using a sand mix concrete to level appropriate if I will then be using ditra as an uncoupling membrane?

    • Roger

      Hi AR,

      Although it’s likely too late (sorry), a sand mix cannot be feathered to fill in low spots. You can, however, use a cementitious floor patch to level out the floor before installing the ditra.

  • Rici

    BTW…our living room is 23×21 and only 1/3 of the way finished. So wondering if we need to prep the leveled floor somehow before proceeding further.

  • Rici

    Hey Roger,
    I had a “tiler” bust out tile throughout my home about 1000sf +/-. He then said he’ll need to put leveler (28 bags total) and laid about 1/4 of the tile and walked off the job!! MIA…my new tiler asked me yesterday if he used primer before pouring the leveler on?? I’m sure he didn’t bc I didn’t pay for it when I paid the $900 to Lowes. Do you think this is a huge issue?? My new tiler said he’s never used leveler without primer and our tiles may lift in a few months…:(

  • Denis Blaquiere

    I live in SW Florida and hurricane Irma recently paid us a visit. Our Florida room used to have carpet that the prior owner installed but we ripped it up a couple of years ago as it had gotten real funky being exposed to wind driven rain (tropical storms and hurricanes). We figured now was a good time to lay some tile but my question is that there is a residue of the old carpet glue covering the entire floor. I thought it was stable but after a good soaking by Irma some of the glue “bubbled” up. It scraped up no problem. Do I need to remove all of it or will the thinset work over it i.e., setup ? I have gotten conflicting opions from different tile stores and contractors. Some say remove it, others say leave it as long as the floor is dry and the old glue is stable. What do you think ?

    • Roger

      Hi Denis,

      It needs to be removed, thinset will not bond to it. The easiest way to do that is to let it soak in water for a bit then scrape it off. It is water soluble, so if you leave it, whether it is ‘stable’ or not, and anything happens that gets it wet – your tile is no longer going to be bonded to your substrate. A tile installation is only as stable and durable as what it is installed over. Water soluble glue is not a great substrate. :D

      • Denis Blaquiere

        Thanks for the reply. I have been soaking the entire floor, 15′ x 33′, with a hose for the last few days. As long as I keep it wet the glue will “bubble up” and then I am able to scrape it up. Long, tedious process but it works.

  • Allysn

    I have a 5’x12′ bathroom with OSB subfloor. This bathroom is down to the studs, and about a third of the floor slopes just over half an inch. It seems to run along a joist (turns out this was the builders first house). We’ve had it inspected for structural, termites, rot from water damage, and structurally fine. The room around it we were about to fix when we installed hardwood.

    We would like to install tile in this bathroom, and I read the primer for self leveling cement is not appropriate for OSB. I am not sure how else to level this floor for tile. Do you have suggestions? I am all ears and want to do a good job that will last.

    Thank you.

    • Roger

      Hi Allysn,

      I have used primer and slc over quite a few floors without issue, including in one of my own bathrooms. I would go that route. These companies have one thing in mind – covering their ass. If there is even a minute chance that something can happen they’ll just tell you not to do it. Whenever you’re going over wood something can always happen. Your slc will be just fine.

  • Yann

    Hi Floorelf,
    Renovating bathroom 96″X84″. Subfloor is 3/4 inch plywood.
    Along the 96″ length the last 20 inches of the subfloor slopes down by varying depths between 1/8″ and 1/32″ along the joist.
    I’m putting 1/2 inch plywood tongue and groove on top as a underlayment, then Ditra heat and porcelain tile. Can I simply ignore the slope or will it compromise my tile install?

    • Roger

      Hi Yann,

      You can ignore a slope that small. What would help is, as you are adding the ditra-heat mat, place a little extra thinset beneath that area and embed it with a straight-edge so it’s flush with the rest of the room. Once the thinset cures that slope will be gone.

  • Rob

    Hello Roger I got bathroom and it’s about 12 ft long and it drops3/4 of inch from center to out side. You can’t tell by eye but with leaves you see it. I’m tileing room 12×24 tile. I’m running tile width short side to low side’ I think you won’t see it low as room is flat. What do you think
    Thanks Rob

    • Roger

      Hi Rob,

      As long as it’s flat it really won’t be noticed. Just don’t sit your golf balls in the center of the floor and expect them to stay there. :D

  • Pam Horner

    I have purchased 8×8″ gauged straight edged quartzite tiles as replacement for cracked porcelain (badly installed) pool bath, entry, and wet bar floors, some are concrete subfloor, some are raised plywood subfloor (not both in any case). The store said I should wash and seal them first. However, if I seal the bottoms and edges, the thin set and grout would be adhering to a thin coat of sealer, instead of the more porous stone, right? Please advise.

    • Roger

      Hi Pam,

      Not necessarily. You’re thinking of a sealer as a coating – it isn’t. A penetrating sealer soaks into the pores of the quartz, it doesn’t ‘clog’ them up. Thinset will still bond to the quartzite just fine. You DO want to make sure you use a white thinset if your quartz is lighter in color. Gray thinset, especially when wet, can randomly darken the look of stone from the front.

  • Zack Jones

    Hey Roger,

    I’m installing 15″x30″ tiles and I the floor is fur plywood. I am installing a uncoupling membrane down but I was wondering I should use self leveling cement before or after the membrane.
    The floor has dips of about 1/16″ (heavy) in some spots while using an 8ft level.

    • Roger

      Hi Zack,

      No need for self leveler with that small of a variation. What you can do is use a long straight-edge while installing your ditra. Spread out your thinset and embed the ditra into it with the straight-edge. Let the thinset cure before walking on it and you’ll have a completely flat substrate. With variation that small the amount of thinset from your trowel while your setting tile will more than make up for it.

  • Gene

    Hi Roger,
    I’ve hired a contractor to install 10×40 wood-look porcelain tile in the living area, kitchen, and bathroom. When removing the old tile they cut many shallow, some deep (up to 1″) gouges and pits in the concrete. Now they are applying the tile directly to the pitted concrete and claiming the (mapei) mortar will fill the holes. They said they never use leveler unless it is really really bad. I’ve insisted they use leveler in at least the kitchen which looks like the face of the moon. Today I realized they are using 1/16″ spacers which I’ve read are too small and were sawing the tiles with a handheld round saw, balanced on a bucket instead of on a table. Should I believe them or consider shaking them loose before we proceed further? Thank you so much for your help.

    • Gene

      Update: they are saying the reason is to match the level of existing tile which is fair as the existing tile appears to also be directly on the slab.

      • Roger

        Hi Gene,

        Many installers have many different methods. While their method may sound unusual, it does not, as far as I can tell, violate any ‘rules’ for an installation. The methods and tools used are relative to where they’ve been trained to install tile. I’ve worked with many foreign-trained (so called ‘third-world’) setters who could cut a tile with all sorts of different hand tools faster than I could with a wet saw. The end result is what you should be concerned with – not so much the journey. :) It may seem unorthodox, but some guys just work like that. As far as the 1/16″ spacers – I use them all the time. Much of the time on tiles that they should not be used on. It has more to do with your skill level.

  • DaveB

    Hey Roger,

    I thought I did a great job building up and flattening my floor with plywood and SLU but ended up with some hairline cracks where I really did not want to see them…

    I did an SLU pour over RPM mats about 3 months ago. It’s a big rambling ranch house and I am running wood-look tile all the way down from mudroom thru the kitchen and down the hallway (@52ft long).

    The home is essentially two rectangles joined together to form a “T” shape. Where those two rectangles meet I had concerns because there was a slight change in height between the two floors (maybe 1/8 -1/4″).

    5/8″ subfloor got an extra layer of 23/32 over it to build it up. Underneath there are doubled 2×10 (4×10) joists 16″oc. When I was bridging the spot where the two rectangles meet (in the hallway) I shaved the underside of the plywood to around 5/8″ to help bridge the height difference . I used adhesive and screws into the joists here because I didn’t want drastic separation of the plywood and subfloor over this bridge point. I normally purposely avoid hitting the joists so this was probably a mistake.

    I glued down the RPM mats with Roberts 2001 and put some staples in the mats to keep them from sliding while glue dried. Laid Nuheat wire, primed and did a continuous pour (TEC SLU) down through whole house. All areas were poured at least to the top of rpm mats. This transition area in the hallway was a bit thicker (@1/2″ thick).

    I had a knee injury and had to leave the job unfinished for last 3 months. I covered the floors with fabric to keep it clean. The area was however walked on quite a bit during this time. Although I feel the floor is structurally sound I’m guessing that walking on the SLU for 3 months stressed the SLU. Because when I went to give the floor a wipe down with water I found 4 hairline cracks running across the floor around this transition area that was bridged with Plywood and RPM\SLU. 3 cracks run about 70-80% across and 1 crack all the way across. See picture attached.

    They are faint hairlines (like a thin pencil line) but you see them better when wet. Tapping across the area with a screwdriver handle doesn’t sound hollow anywhere. They are not crumbling and I feel no movement. Way too thin to get any kind of knife or tool in there. Heating cables are working fine.

    I also have 2 or 3 wandering hairlines in the kitchen area (@ 2-4ft long). Nothing across the whole floor though. For those I mixed a little TEC Multipurpose primer and water and applied to the hairlines letting it bubble down and soak it in till it wouldn’t take any more.

    I’m wondering if I should just put some primer in these 4 hallway hairlines and continue on with tile or if I should maybe Nobleseal TS over the entire floor or at least this hallway\transition area to ensure future cracks don’t transfer up to tile?

    What are your thoughts? I know some hairlines are somewhat normal with wood movement and RPM does hold SLU very tenaciously.

    Have you ever used or seen NoblSeal TS put over radiant SLU before tiling (over other similar membrane)?

    I was already going to add soft grout joints zigzagged across this tile work (in same direction of these hallway cracks actually) so I guess I’ll add an extra soft joint at this hallway hairline area to be safe. I’m also going to add some extra blocking under this these 4 cracks just for extra support.

    Any advice is much appreciated. Thanks!

    • Roger

      Hi Dave,

      I don’t see a picture at all on your comment. However, you did state that the slc was thicker at that spot, so it makes sense that you may be seeing shrinkage cracks there. They are nothing to be concerned about. They happen whether it’s been three days or three months. It doesn’t affect anything. I wouldn’t worry about TS over the installation anywhere unless you really feel like you need it, if so it’s completely acceptable to install it in that manner.

      • DaveB

        Thank you for that quick reply! I’ve tried attaching those pics again just to show you. I wasn’t looking to do the NobleSeal TS unless you felt these cracks portended future failures done the road. Takin my time to do it right so I don’t have problems down the road.

      • DaveB

        Hmm. Uploading various pic formats still not working. Here’s a link to the SLU cracks, plus a picture of the plywood spanning the subfloor joint.

        • Roger

          Yup, shrinkage cracks. If you notice they begin at a corner on either side of where the slc is thicker, the thicker portions were simply pulling more as it shrunk and it pulled away from the thinner, cured portion a bit. It’s nothing to worry about, I wouldn’t bother with the TS.

  • Brian


    So I ripped up my kitchen floor. It appears to have a leveler on the concrete already. My installer said he may have to install a new subfloor to tile over. This seems wrong, can I not just sand the old leveler and place a new one? IF that is even needed ? The floor is perfectly flat already.

    Also, can leveler be cleaned ? In case of mold or any other issues ?


    • Roger

      Hi Brian,

      It depends on the shape the leveler is currently in. It may be sufficient, it may not – I can’t see it from here. :D You can go over leveler with leveler (if it’s in good shape). It cannot, to my knowledge, be cleaned.

      • Brian

        Here are a few pictures, if that helps at all.

        So options would be re level or sand down and level ?

        Thanks for your help!

        • Roger

          Yes, those are your options unless you want to go directly over it with a membrane such as Schluter Ditra.

  • Sarah

    So I have pulled up all of the tile and vct and floating floor in the house and am left with a messy concrete subfloor. I bought tec self leveling underlayment. Its just me working on this so I could only manage one bag at a time. The issue I’m having is where the has met up in some areas there is a very slight height difference. (very very slight) and also some of it is extremely smoothe and in some places a little rough. Before I paint on the vct adhesive, I want to make sure everything is as close to professional as it can be. So I need to smooth these areas where the bags met up or are slight imperfections not noticable when using vct glue and luxury vinyl planks?

    • Roger

      Hi Sarah,

      Every imperfection will show through with lvt. Get some feathering floor patch to go over those areas. You mix it up and spread it on with a trowel, you can flush everything out like that.

  • Ryan


    SOS… I have a bathroom in remodeling right now it’s 8′ 6″ x 12′. I replaced the subfloor with 3/4″ advantech T&G and then added a second layer of 3/8″ plywood over it. I am using a ditra uncoupling membrane and 36″ x 6″ porcelain tiles. Here’s my problem… I checked my floor (or thought I did) for level before laying the ditra. Tonight i was cleaning up and noticed my level laying on the floor and against one wall the floor is 1/4″ out over about 16″. The rest of the floor is flat and level but up against this wall (8 one of the 8′ 6″ walls) the floor slopes! Is there anyway to correct this now that the Ditra is already set?

    • Ryan

      Maybe this is a dumb question… The mortar I’m going to be using to install the tiles is Mapei Uncoupling Membrane Mortar. Since I’m using LFT tiles this is a medium bed mortar. My understanding is that medium bed mortars are made to be applied thicker than a thinset. Could I use the medium bed mortar over the ditra and build it up 1/4″, let if cure then come back over it with my tile?

      • Roger

        Sorry, I see the questions in the order they were submitted. :) You can do that as well, but the ditra idea works much better.

    • Roger

      Hi Ryan,

      You can fix it, but it depends on how it slopes (you didn’t say). If it slopes UP (that area is higher) just cut the ditra out of that area. It’s small enough that not having ditra under that particular spot won’t make any difference. If it slopes DOWN just cut a strip of ditra and install it over the existing ditra.

  • 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?

    • Roger

      Hi Paul,

      It’s fine.