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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John

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

Reply

Roger

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.

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Ralph

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?

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Roger

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.

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Ralph

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?

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Roger

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.

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Sean

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.

Reply

Roger

Hi Sean,

It should be no more than 1/4″ in 10 feet and no more than 1/8″ in two.

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Brian

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.

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Roger

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.

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Nathan Souza

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.

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Roger

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. :D

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.

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JP

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

Reply

Roger

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.

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Troy

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……

Reply

Roger

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.

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Wayne

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.

Reply

Roger

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.

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wayne

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.

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wayne

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.

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Roger

Yes, the versabond is just fine. As is the 252.

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Dave

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

Reply

Roger

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. :D

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Adam

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

Reply

Roger

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? :D

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