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.
{ 13 comments… read them below or add one }
Hello, Roger. Thank you for sharing your professional experience for us DIY’ers who simply need accurate information without requiring an act of congress to get it! My wife and I are nearing completion of a bathroom renovation and will be tiling the floor soon. We gutted it down to the sub-floor, which is comprised of 1″ x 6″ planks (quite sturdy). I plan on using thinset and screws to secure the backer board, and then tape and mortar the joints before tiling. I have a few questions…
1) I chose the 1/4″ Hardibacker product as my base. What notch size should i use for the thinset? is the 3/4″ subfloor plus 1/4″ backer board a thick enough base to install 12″ x 12″ ceramic tile?
2) After thinset and screws, can the surface be walked on? or do i have to wait 24 hours before going over it to tape/mortar the joints and then another 24 hours to tile?
FYI – thanks to you, i have a rubber-ducky-storing hole in my shower wall. Your step by step articles and information about Kerdi were so helpful. I sleep well at night knowing my tile installation will last a long time.
Hey Aaron,
I use a 1/4″ x 1/4″ u-notch (square notch) trowel beneath underlayment. You are *technically* supposed to have 1 1/4″ total height on your subfloor for proper deflection ratio and adequate support for tile. This includes two layers of plywood (or the planks with a layer of plywood screwed to them – not to the joists). The hardi is simply there as the suitable ‘adhesion’ layer for your tile. You can probably get away with a layer of 1/4″ plywood with the hardi above it or the hardi with ditra above it. (Don’t tell the tile police I told you that)
You can walk on the surface as soon as you have it thinsetted and screwed down – no need to wait.
Glad to hear you have rubber ducky storage! I’m gonna start a ‘save the rubber ducky’ movement – keep an eye out for the chapter near you!
I have a similar problem as Kathy above does, But mine is that previous owners of the house mortared and nailed the cement board on top of the old vinyl floor. I was able to pop off the tile leaving the mortar pretty much in tack in a 4×10 foot area of the kitchen. I then spent 4 hours using a rented hilti demo hammer breaking up that small space (what a mess)! So the questions are —
- Do you have a better way of getting cement board up (I tried a scraper ran into the nails, a crow bar to slow)
- Is OK to tile over the existed mortar that is on top of cement board?
- What would use to fill the areas were the mortar comes off with the tile?
Thank you
Justin
Hi Justin,
Unfortunately you’ve found the best way to remove it. When it is done correctly (with mortar beneath the cement board) it is a pain in the ass to tear out – as it should be.
Whether or not it is ok to tile over the existing mortar is a question only you can answer. How well is it adhered? More importantly, what is beneath it? Any tile installation is only as good as what it is installed over – are you confident that the present substrate will not move and compromise your new tile installation?
You can fill those areas with thinset. You can do it as you go along or fill all the areas and basically get your entire substrate flat, let that cure, then tile as normal.
Just as an aside I will always tear the existing floor down to either an absolute solid substrate or the joists. I do this simply because once I install the tile I own that installation. I don’t know how the existing floor was installed nor what may be beneath it so I simply don’t chance it. Yes, it takes more time and it is a pain at times, but I sleep very well at night.
Hope that helps.
Thanks for the quick response. The granite is called planetla brown( Looks light with black and maybe some gray specks) and is a lighter granite. The thinset is Tec white adhesive(Looks light gray). I read the whole bucket and at the very bottom it says it may discolor some marble and granite. I should have read more and trusted the sale associate less. I will tear it off. Thanks Russ
Hey Russell,
Hate to hear that. The best thing to set any natural stone is with a product specifically made for that. Versabond makes a granite and marble set and it is available in white or gray. A lot of manufacturers will include the negative aspects of their product at the very bottom of the instructions. Be sure to read everything.
You did state “on the bottom of the bucket…” which, to me, indicates that you are using a “pre-mixed” thinset. That is actually mastic with sand in it – it should never be used in a shower or for natural stone of any type. You want to get a powdered thinset which is sold in bags that you mix with water. Mastic is an organic compound which contains oils that often affect natural stone.
A general rule of thumb for tile setting – if it is pre-mixed do not use it. That includes grout, mortar, or anything else. Anything pre-mixed will ALWAYS need air to dry or set fully. If you place a 12″ tile over something that is pre-mixed it is just like putting the lid back on the bucket – the adhesive will NEVER fully cure. The plus side for you, Russell, is that it will be relatively easy to remove your tiles and clean them off.
For anyone using a lighter stone you always want to use the white thinset to set it. If you are unsure whether or not you should use white due to the shade of your stone, use white. White will not affect darker colors except black and very dark stones but the gray may effect anything lighter than the color of the thinset.
Hi, My wife and I have just install granite in our bathroom in the last 12 hours. I used DensGuard as my back board. In the last 12 hours the tile has gotten darker. The thinset says it can be used with granite. Is this a drying issue? Should we let it set longer before we grout? Thank you.
Hi Russel,
It sounds to me, and I may be incorrect since I can’t see your bathroom from here
, that you have a lighter colored granite and you used a gray thinset. Is that correct?
If it is I’m afraid there isn’t much you can do short of tearing it out and starting over. Gray thinset should not be used on lighter tiles (natural stone, mostly) as it may darken the tile.
If that is not correct can you please tell me which granite color you used and which specific thinset? It would help nail down the best solution for you.
If that is what happened you may be able to live with it by either picking a grout color that matches the current granite – as it looks now installed, or picking a lighter grout which may help distract from the darker tile.
Or, since it’s been only twelve hours – get it out before it sets any more. That will be a LOT of work, just so you know. Sorry, I know that isn’t what you wanted to hear.
I just took up about 800 square feet of ceramic tile with an air chisel. While the tile came up nicely, much of the underlying thinset is still stuck to the concrete subfloor. After calling several rental places, they all said that they have so many problems with their floor sanders for this type of application. Since we are planning on tiling over this area again, would the new layer of thinset be enough to make the floor flat under the new tile?
Hi Kathy,
I’m assuming your floor is concrete. Please correct me if I’m wrong. There are a couple of ways to go about that. The best, of course, would be to chip all of the old thinset off of your floor. You can do this with a floor scraper for the most part. Any small areas left after that can be chipped off with a hammer and chisel or screwdriver. Sanding it down is more of a pain than it’s worth. It usually has marginal results as well.
If you cannot get all of it off it may be easier to level out the floor, as you’ve stated, with thinset. It is easier and faster to do this as you set tile. This is only and option if the thinset that is currently stuck is no more than about 1/8″ high. You do not want to try and fill in too much area with simply thinset.
If it does not all come up and you end up having to float it as you set tile you should use a medium-bed mortar rather than regular thinset. Use a 3/8 or, better yet, 1/2 trowel on your floor. The medium bed mortar gives you much more support and allows quite a bit of mortar beneath the tile with total support – your tile will not sink into it as it would tend to do with too much regular thinset mortar.
Thanks for getting back to me so quickly! Well, that puts my mind at ease. Off to Redguard the floor!
Julio
I have a floor that I used “self-levelling” compound on and, while it is in better shape than when I started, still have a few dips here and there of about 1/8″ or so. I’ve heard thinset can be used to offset some floor variations, but how far can I push that?
Thanks. And by the way, great site and great info!
Julio
Hey Julio,
ANSI standards state that the maximum variation for acceptable flatness for tile installation is 1/8″ over 10 feet. So your floor qualifies.
An 1/8″ variation is no problem. Your thinset (when properly mixed) can fill voids up to and including 1/4″ (although that is pushing it in my opinion). You shouldn’t have any problems fixing that variation with thinset.
An additional alternative would be to use a medium-bed thinset to install your tile. The only difference is that the medium-bed has more sand in it to prevent your tiles from sagging or sinking before the mortar is fully cured. It is a bit stiffer and tends to add more support to your tiles as it sets. That would make it easier to end up with a flat tile installation but either should do just fine.
Thank you for the kind words! If you have any more questions at all just let me know.