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.
Hi Roger,
Kitchen remodel underway. Contractor pulled floor down to a layer of previously existing laminate, screwed floor board to the joists and put down “wonderboard lite.” I wanted my 6×24″ porcelain tile installed vertically (the length of the house), into the eating arresting area (sorry don’t have measurements). It’s a rectangular area. Contractor saying unable to flatten the floor enough to accommodate that. Therefore, tiles to be installed horizontally (the width of the room). To my eye it will shorten the room and not look right. We asked about SLC or building up the floor. Contractor said not possible. Is he being lazy or trying to cut corners to finish our remodel faster?
I want tile to run the length of house, from kitchen to eating are, not arresting area.
Hi Darcy,
Absolutely it’s possible. You’ll have to pay for extra prep to get the floor flat if that’s the problem, but yes, it is possible.
I am going to have my bedrooms installed with tile (at least 18 x 18 inch). My home is on a concrete slab. A tile installer came out and when I asked him about making sure the floor was flat, he told me he would use his laser level to determine the high point of each room and then build up the lower parts with the thin set to get the floor flat.
Is this an acceptable way to install tile without “lippage”? (I was hoping to go with 1/8 inch grout lines.)
Hi SA,
It depends on how out-of-flat it is. If there is more than 1/4″ variation then it should not be built up with thinset.
Roger,
We are tileing the front steps of our craftsman stlye home. The brick stupe on each side has pulled away from the stairs over time. What can I fille the cracks with before tileling? The cracks are about 2 inches wide and go all the way to the ground.
Lynne
Hi Lynne,
Regular concrete will work fine.
Hi Roger,
I am in the process of remodeling a small bathroom (80sqft). I have removed the old tile and ground down the old thinset. There are some imperfections in the floor, nothing really major. Would you recommend putting down an underlayment membrane to ensure a suitable surface for the new tile that will be going in?
On a side note your site seems to be one of the most comprehensive and informative I have found on tile. Thank You!!
Hi Jason,
I normally always recommend a membrane over your substrate. It is always technically required, but it is normally always beneficial.
Roger,
I’ve been reading your site, very good information here. I have a 50’s bungalow with a 3/4in plank subfloor. 8inch joists, 18in centers. This is a bathroom remodel with a corner shower (pan), pedestal sink and toilet. I’m going with ditra per their specs. 15/32 ply screwed to the planks, modified thinset, ditra, unmodified, 2inch hex mosaic. The floor is very flat, no peaks or valleys. It does slope from one wall to the opposite, in only one direction. (As though part of the house settled.) The bathroom is small, 72×60, and over the 72 inch span it drops by about 3/4 of an inch. Do I need to worry about leveling the floor?
Thanks!
Hi Joe,
Not unless it’s extremely noticeable, or it’s gonna drive you nuts.
It’ll be fine the way it is.
Roger,
Thank you so much! I used a furring strip to install the wall tile perfectly level, then installed the last 2 rows down and cut the tiles to fit. Hardly noticeable at first glance and should be nearly unnoticeable when the toilet goes back in. And yes, these things make me nuts!
Hi Roger
I have a problem .. hope you can help me. I put tile (wood tile) in a room, and in some places one tile is a little bit higher than the next tile just in the shorter part of the rectangle. what my client does is go with socks all over the floor trying to find those differences in the level between one tile and the other. What shall I do? Replace the tile with the problem .. then don’t you think that I will have problems in the opposite side of the tile.
Thanks in advance for your help
Regards
Rob
Hi Rob,
If you remove and replace the tile that sits lower you should be able to match up the other side of the tile without problems. If you try to lower the higher tile you will have problems with the other end of the tile.
i have a guest bathroom that is slightly off near the toilet. I think I will have to level it which might be the whole room (have to look). What should I use to make a barrier at the walls?
Hi Mike,
Pink or blue sill-seal foam sold in the concrete section.
I am trying to redo a basement bathroom and want to tile over concrete which previously had laminate covering it. I have removed the laminate, but some of the glue still remains, do i need to remove it and how can i prepare the floor for the tiles (16 x 16) the easiest way without having a large step up into the bathroom. Can i put my morter/grout right on the concrete? or do i need some kind of buffer?
Hi Trinity,
You can bond it directly to the concrete without problem. Any glue needs to be removed from the surface with scraping, mechanically scarifying or chemically etching. The slab needs to be able to soak in water when you splash some on there or it will not allow thinset to bond well to it.
Grouting question. Grouting a shower that has an accent tile which will be grouted with white unsanded grout an the rest of shower will be grouted with sanded grey grout. Question which should be done first white or grey and why?
Hi Richard,
The gray should be done first. The gray will stain the white if the white is done first, the white will not stain the gray.
Hi Roger,
Im tileing a a mud room in my house which is a concrete slab. Ive used slc becasue it has a slope on one side and was able to get it flat for the most part but not level. Ive used ditra and have started to lay the tiles. It is a long room 6ft x 20ft Now that I am about 3/4 of the way done I can see the slope of the room in the tiles but my tiles are laying flat “no lippage” I guess my question is does this sound correct or should I have tired to level the floor more? slc is not cheap and to get it perfect would of gone over the 1 inch build up that is allowed. Just frustrated because the tile looks good but I can see the pitch in the room. FYI the window lets a ton of light in which doesnt help.
Hi Anthony,
As long as it’s flat it’s just fine. Once finished it will be hard to notice at all (for everyone else – you’ll see it every time you walk in there
).
Can I use a tile leveling spacer system to compensate for a poor pouring of an sock that left me with sections that vary by approximately 1/8″? DespeRately want to end this home remodeling project. I have just my kitchen and half bath to tile.
Hi Vanessa,
Not really. You can use it to hold them in place while the thinset cures, which is what they do. You’ll need to just add more thinset beneath the lower areas as you set the tile.
hi rodger im tiling 2 way sloping surface and i want to change the level of my tiles how can i do this without creating lippage ? regards matt
Hi Matt,
I’m not quite understanding what you’re asking me. Are you changing the level of the tiles at the top (or bottom) of this slope? Why do the tile levels need to be changed? Changed from what? I’m just not getting it (not unusual if you ask my wife…)
Hello Roger,
I’m working on a small bathroom floor (32″×60″) with a concrete substrate. The exiting floor finish I have to work with has old black mastic from the ’50’s (probably contains asbestos). I’ll be installing a heat mesh mat under 8″×20″ marble tiles. My questions are: A. Can I lay tile over the black mastic without removing it? B. Is it wise to lay the mesh mat directly over the concrete and tile with thinset all at once as the manufacturer suggests (worried about the mat’s thickness creating uneven buildup and not keeping the floor flat). C. Would you recommend using an uncoupling membrane such as ditra or a fluid product over the concrete. Desperately concerned about lippage.
Thank you for advice.
Todd
Hi Todd,
Your best option is to prime the floor with an slc primer, lay down your mat, and pour slc over the entire surface. This will embed the mat, give you a flat surface and deal with the cutback (the black stuff). WAY easier than any other option.
Hi Floor Elf,
Your website has been a huge help to us through our bathroom remodel. Our steam shower came out excellent thanks to your advice. We’re working on the floor now and have a slight glitch.
We’ll be using 12″ square tiles on a bathroom floor with epoxy grout in 1/8″ lines. Our buildup is: plywood subfloor, Hardibacker- (thinset, screwed correctly and mesh taped on the joints), Laticrete waterproofing (because we had it left over and it’s expensive), radiant heating cable, a bed of modified thinset to bed the cable and to flatten the floor, Ditra applied with unmodified thinset with the seams and edges “taped” with Kerdi for waterproofing. Despite the best efforts we have some un-flat spots that fall outside the acceptable tolerances for a flat floor.
Is the best idea at this point to apply a layer of thinset over the Ditra in certain spots to make the floor as flat as possible before applying the tile?
Will these filled in areas act as unstable substrates or cold joints, or will they bond with the unmodified thinset used for the tile application and act as one unit on top of the Kerdi?
Can we use some leftover modified thinset to fill the areas and use unmodified on top of that?
Thanks Floor Elf!
John
Hi John,
You can fill those areas either now, and let it cure, or just do it as you are setting the tile, placing more thinset in those areas. Doing it first and letting it cure is probably best, that way there isn’t any surprise shrinking after your tile is set. It will be just as stable as the surrounding areas.
i’m putting in radiant heat and Leveling the deck mud over the radiant i plan on using screed boards and a straight edge to screed the mud for a flat surface is that an accurate method?
When doing a mud floor you create the screeds with deck mud in two or three long runs down the room, then fill between them and use a straight edge to screed it level.
I’m doing a mud floor and its alarge surface, i’m doing half at a time. Is there anything i should know about stoping the mud job and starting it up a week later?
Hi Ralph,
If you stop mud in the middle of a job you’ll have a cold joint. You need to begin again by putting thinset against that cold joint and you need to have a soft joint directly over the top of it through the tile.
Hi Roger,
I’m going to tile a concrete slab with 12×24 tile and had a question about the flatness of it. When ripping up the old tiles, I made craters in the concrete. I went back and flattened most of them so the maximum depth of the holes were less than 1/4″. My question now is, can I use thinset when I begin tiling to fill the small craters that I made since my slab is not perfectly flat?
Hi Neville,
Yes you can.
Hello
I am currently in the process of finishing my basement. I have already done all of the walls and all of the ceiling. Now, I get to start on the floor. I am going to install 13″x13″ ceramic tile. I am wondering exactly how flat the floor needs to be. I have put a straight edge to the floor, and while it isn’t perfect, the variance is only about an 1/8th inch at most. Is this flat enough that I can compensate with my thinset, or do I need to level the floor first?
Thanks for your help.
Hi Sean,
It should be no more than 1/4″ in 10 feet and no more than 1/8″ in two.
Im planning on putting ceramic tile down in my finished basement. i noticed some areas are flat and some are not. do i need to cover the whole floor in self leveling compound or just the affected areas. also what is the best way to fill holes that i made when i had to pull hundreds of nails out of the floor “it had carpet before” a few times it chipped out a few inches of cement as much as 1/4″ deep.
Hi Brian,
If those spots are lower then you can just fill them with slc. If they are higher you can grind them down or cover the whole floor with slc. Thinset will fill those nail holes.
I don’t think that your floor has to be level in order to install tile. I have seen many cases where the floor is not completely level but there is tile installed. Tile is one medium that is actually surprisingly flexible. It is good for waterproofing your basement or bathroom floors as well.
Hi Nathan,
I have removed your link, my site is here for diy’ers, not as a marketing platform for your business.
As TILE IS NOT FLEXIBLE, in any way, shape or form! Nor is it waterproof. But thanks for the laugh.
If you’re going to be a contractor I beg you – please get educated on the products you install in people’s homes. Or if, as I suspect, you are simply the online marketing person for this particular company, please find out what the hell you are talking about before you represent a company’s interests. Thanks.
Roger –
I’m doing a gut rehab on a small upstairs master bath on a 50-year old two story house. The original tile had held up well: the substrate was 2 layers of 1/2 ply (1 layer original subfloor, 1 layer add-on) separated by tar paper that was topped with another layer of tar paper, metal lath, 1″ of deck mud and then the tile. I assume thin set was on top of the deck mud, but couldn’t really differentiate during the demo.
I pulled up all of the supplemental 1/2 ply and needed to cut out a few sections of the original subfloor to reconfigure plumbing. In replacing the sections of original subfloor, I’ve noticed that it is terribly wavy – sagging between the 16″ OC joists below. My question is: at which layer should I focus on leveling? I plan to replace the supplemental 1/2 ply after the subfloor is repaired. I will thinset in 1/2 of hardibacker on top of that before laying my large format floor tiles (18 x 12). Should I just screw down the extra 1/2 ply and use the thinset liberally to lay the hardibacker flat?
Also, this brings up a question on which the blogosphere tends to disagree: do I glue and screw the 2nd layer of ply to the first, or just screw it down avoiding the joists and allowing for movement between the layers?
WWRD? (What would Roger do?)
Thanks,
JP
Hi JP,
Roger would follow the TCNA and ANSI standards and place the second layer of ply over the first – WITHOUT GLUE – and screw it down avoiding the joists. You can level it with the thinset beneath the backer provided you’re not out of flat more than about 1/4″ or so. Spread the thinset, bed the backer into it and get it level and flat with your straight-edge, then let the thinset cure. The next day go in and screw it down. If you screw it down before the thinset cures it will not remain flat.
Alternatively you can just install the backer with thinset beneath it, screw it down and use self-leveling cement over the backer to level it out. First is (much) cheaper, second is easier.
Hi Roger,
I am doing a few tile projects in my home and I am using a RUBY TOOLS Leveling system to help with lippage.
I find the system works great except…… when I am stopping the project from one day then returning to it the next.
That row of tile I can no longer get the leveling clips under the SET tile due to the mortar drying by then and when starting the new row I find it is very tough to get it exact without any lippage at all. I am finding when I stop and start on a new day there always seems to be a wee bit of lippage on those tiles. Not by much but, I am a bit of a perfectionst.
What are some options to stop this from occuring?
Thanks……
Hi Troy,
Just place the clips under the open end of the installation when you stop for the day. The next day place your next row of tiles and tighten down the clips from the previous day. Let the thinset cure with the clips already in place.
Roger,
I am planning to tile approximately 950 sqft with a 6×24 porcelain plank tile over a concrete subfloor. The most intimidating part of this whole job is getting the subfloor flat enough to prevent lippage. What is the best method to flatten a large area like this? I have looked into SLCs but they are very pricey. Do you have other suggestions?
Also, I was planning to lay down Laticrete’s Strata Mat to isolate the tile install from the concrete. Is this necessary or can I use something else to create the isolation. I saw an install online where they used something over just the cracks in the concrete. I assume that would only isolate horizontal movement. Again isolation membranes like Strata Mat are very pricey. I don’t want to sound like a cheap hack but I also don’t want to do like many DIYers and spend money where it is not necessary. Any advice would be very much appreciated.
Hi Wayne,
SLC is your best option to get a concrete slab flat. Strata mat is not required, but always a very good idea over concrete. What you’ve seen is a crack-isolation membrane, it only deals with in-plane movement (as any membrane will) but only over where it is placed. The properties of strata mat or ditra that do the same thing do it for the entire installation.
It sounds like the SLC is money well spent.
I haven’t seen my slab yet so I haven’t made the decision to use Strata Mat. Most likely, I will use it just for peace of mind. With that being said, is Versabond a good enough thinset to use? If not, is Laticrete 252 Sliver? I would have to get the 252 from Stone Tooling. The Versabond is available at HD. I have Lowes and Menards at my disposal as well.
Thanks for your time and all the great advice. Not too many people would go to this trouble.
Disregard above. Can’t get Laticrete, shipping too much!
I only have access to HD – Custom, Lowes – Mapei, or Menards – TEC. Florida Tile also carries TEC.
I would like to use same product above and below Strata Mat. I have heard it can be done since the mat has hydration vents.
Thanks again.
Yes, the versabond is just fine. As is the 252.
Hi Roger,
I have a customer I have done a couple of tiling jobs for, nothing spectacular. However he is very intent on hiring me to tear out some marble tile in his personal residence, a rather intimidating house, and replace it with large 24″ porcelain tile. I believe it would be around 700 – 800 sq ft. I feel overwhelmed by the prospect, and yet also would like to tackle a job of that scale. My main concern is that I have heard rumors from guy who saw the current marble installed, that the sub-floor is very uneven and needed a whole lot of building up with mud in order to keep the floor flat. I am not terribly experienced with real large tile installation and am not sure how I would address the sub-floor. Since this would be a remodel, I have other floor transitions to match. Was wondering if you run into a lot of these types of situations and appreciate any advice you could think to give me. Also, which brand of snap cutter would you recommend? I would like to purchase one for larger tile. Thanks so much.
– Dave
Hi Dave,
I’ve done a few of them. Your best bet is to remove EVERYTHING beneath the marble, down to the substrate. At that point determine what method would best help you achieve a flat floor with smooth transitions. Deck mud is actually my preferred method, but an SLC may suffice. It just depends on how much buildup you may need.
And I use Sigmas. They are the best I’ve ever used, and never let me down.
And DO NOT undercharge for this! Don’t underestimate the amount of work involved. I had to pay for that lesson a couple of times.
Hi Roger,
Thanks for your guidance, I found a deck mud that can be between 1/2″ and 1-1/2″. I don’t know if I can get it where I am, but at least I know deck mud exists.
Thanks for the guidance and the website,
Adam
Hi Adam,
If you take a bucket and mix 5 parts sand to one part cement then deck mud will exist in your bucket too. Can you get sand and cement where you are?
Hi Roger,
I would like to install 12″x24″ tiles on an uneven basement concrete floor. I used a scarifier to prep the floor. I already failed once to level the floor with a resurfacing cement product and primer. The product did not bond. I watched a tile setter on a construction site mix thinset and sand mix to fill in dips in a concrete floor. He also told me that it’s possible to first butter the floor with thinset and then fill with sand mix. What do you think of this approach? Is modified or unmodified thinset used in this application?
Thanks for this website!
Hi Adam,
Doesn’t matter what type of thinset you use, it’s not a proper process and I have no idea how long it would actually last. Deck mud can be mixed up and screeded to create a flat substrate, but it needs to be a minimum of 3/4″ thick.