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.
Roger,
Thank you so much for this great site. Nice to be reminded to laugh as we all deal with total tile frustration! Your advice on this situation below would be much appreciated.
I want to level and smooth a bathroom subfloor, then install 12×12 tile. The subfloor is tongue-and-groove 1×4 planking. My plan had been: (1) self-leveling compound, (2) 5/8″ or 3/4″ plywood, (3) ditra – 1/8″, (4) tile – 1/4″. That’d get me finished within the 1″ of clearance I have from the high point of the subfloor to the adjacent finished floor.
But how to level the planking? I found out that most concrete leveling compounds can’t go on wood planking. I need to fill up to 1″ of height. (It loses 1″ across 30″, then slants back up, with a 1/8″ lip at the inflection point.) Other than that, the planking and the joists below are strong and well-attached, and the planking extends under adjacent rooms, so I’d prefer to level from above. How would you do that? Many thanks for any suggestions.
Hi Carli,
You can install the plywood over the planking first, then the SLC, then the ditra. This will level out your floor and you can use the SLC to do so. Just nail the plywood into the planking – not into the joists. And be sure to use the primer for your particular SLC.
Hi Roger,
Thanks! So, I don’t need to worry about the plywood being bouncy spanning a short-but-wide gap like that? I’ve had people suggest gypsum-based Planitex, Henry’s Patch and Level, asphalt shingles… Think I can skip that stuff? Thanks again!
I’m not sure to which short but wide gap you are referring???
There’s kind of a “valley” as the plank floor loses height (about 1″ across 30″ or so), then slopes up again. Maybe I should just get the plywood cut and then see if it feels bouncy. But if it does, any ideas? Maybe I could shim it with some CBU in as you suggested below. (Or is CBU on planking a bad idea?)
Oh, the dip.
The plywood you install should conform to that dip, not float over it. The SLC is what is going to level it out. Don’t be concerned with getting the plywood to lie flat. It is simply there to build the height and give you a suitable substrate for the SLC. Do not try to stuff or layer things under there to flatten it out, it guarantees voids beneath the plywood. Just screw the plywood to the planks securely and let it conform to that dip – level it with the SLC.
Hi Roger,
The information on this site is very useful. We had planned on tiling over the existing ceramic tile in a 5’x8′ bathroom by roughing up the tile, then using unmodified thinset with a latex additive to make sure the new tile bonded well. The problem is, after removing the vanity I discovered that the builders had set the vanity before tiling, and there is only plywood underneath. Because the original ceramic tile was set in a concrete bed, there is slightly over an inch height difference between the tiled area of the floor and the plywood where the vanity had been. What is the best option here to get a flat substrate for the new tile?
Hi Carrie,
Mix up some deck mud and pack it in there up to the level of the existing tile. How to make deck mud. You can tile directly to that.
Thank you so much for the quick response! If I use deck mud, do I need to install plastic or tar paper and metal lath, then thinset, before mixing and packing the mud – like the post about creating a shower base?
Also, before tiling do I have to sand the existing tile and do a skim coat of thinset first to fill in the old grout lines? I have gotten conflicting answers saying yes absolutely, or no it’s not necessary if using good quality thinset with latex additive.
You can forego the metal lath or thinset beneath the mud, no need to in an area that small. Just pack it in there onto the substrate.
In my opinion yes, it is necessary and you should do a skim coat first. Sometimes it’s necessary and sometimes it isn’t – I don’t know without standing in front of it. Why take that chance? You will ALWAYS get a better bond by removing the glaze from the existing tile.
Can I sandwich hardi backer boards together to get the height that I want. I will use thinset between layers.
I have a terribly out of level floor (1 inch off over 5 feet), should I do a mud bed that tapers off to 1/8th inch or 1/16? or can I sandwich 1/4 inch backer boards incrementally and step it down like a pyramid and smooth it all out with thinset????
does this make sense?
Is this rediculous?
Hey Jesse,
It isn’t ridiculous, and it will work, but you’re doing it the hard way. The best way would be to use deck mud until it gets to 3/4″ thick (that’s the thinnest you want to go) and go from there with the backer. Once you get to where it’s stepped up (or down) all you can use SLC to level it all out. You *can* float it out with thinset but that’s hitting the maximum recommended thickness for certain brands. The SLC would be a better option. If you do sandwich any backer you’re correct, make sure you have thinset between the layers.
I have over 700sf of painted (ugh) sattillo? tile in my home. It covers halls, dining and two bathrooms. We desire to install wood in halls and dining areas. We would like to put 13×13 ceramic in the bathrooms. I started breaking the guest bath and discovered thin set and up to two inches of mud on the slab. Should I go to the slab or just repair the mud? Not sure the two floors will match when we tackle the halls.
Hey Pete,
If the slab is in fairly good shape you can just repair it and go over it. If you need to lower it for height reasons you can remove that one and build one to whatever height you need to meet up to the wood.
Great site! Lots of useful information.
I am renovating a guest bath and adjacent laundry area in a slab home which is currently tiled with ceramic over concrete. The adjoining hallway at the door thresholds is hardwood over ¾ inch ply which is quiet a difference in the floor elevation. I have purchased 18” porcelain to redo these floors but need to make a decision.
Since I would like to raise the elevation on these floors to better transition at the door thresholds would it be easier to tear up the ceramic and start over or is it possible to grind off the glaze on the existing floor and tile over it? BTW, the glaze on the ceramic is slick but does not have a flat surface.
I’ve occasionally been accused of having some common sense but this one has me stuck.
Thanks,
Geno
Hey Geno,
You can scarify the surface of the current tile and go right over it provided it is sound and flat and you use a thinset approved for tile over tile installation. Mapei Ultraflex II is a common one, but there are several others.
I have rebuilt the floor in my bathroom with two layers of 3/4 plywood, screwed down and offset, but there is a long 1/4″ slope in the last 2′ downwards towards the bathtub and again towards the door. I don’t want water to go either way. The old tile and mortar bed that I removed had that same water pooling problem. Now I know I should have shimmed the joists level first.
It seems to me that I can gradually build up the necessary slope correction with 2 or 3 layers of thinset on the plywood (drying in between) before I thinset down 1/4″ backer board. Is that correct?
Hey Tom,
Yes, you can float out the floor with thinset. Make sure to check the maximum recommended thickness of your particular thinset (most are about 3/8″ or so) to ensure it can be built up that thick. Other than that it won’t be a problem at all.
Thank you. I figured that thinset would be easier to work with than patching cement or mortar which I would have to bond with some kind of glue. I don’t think fill area is above 5/16″.
It is so lovely to ask someone! What an amazing gift you are to the community at large.
Tom
I’m redoing a 1930’s bathroom. It started out with me just wanting to replace the toilet and I discovered wood rot under the vinyl flooring. Ripped out the vinyl and the 1/4″ plywood floor. What is left is 1×6 diagonal subfloor and 1×3 tongue and groove oak flooring. i hate that you are going to tell me I need to add plywood, cement board before tiling with mosaics, unless you tell me I can use 1/4 ” plywood and 1/4 ” cement board. i thought about ripping up the oak flooring but it goes under the cast iron tub and I’m handy but petite.
Also, the walls are pine shiplap with a linoleum type stuff over that then sheetrock and around the tub there is also the wire lath mortar bed with tile. Lots of layers and need I mention the mold?
if I gut it do I go as far back as the shiplap? Do I need a vapor barrier between the shiplap and the cement board on the walls?
Hi Kathy,
With 1×6 diagonal subfloor and 1×3 t&g you should be able to use 1/4″ plywood and 1/4″ backer without a problem. If you gut the shower then yes, you should go all the way back to the shiplap. And yes, you’ll need a vapor barrier between the shiplap and backer.
thank you, Roger Elf! Your info is a wonderful Christmas gift and the finished bathroom will end up being a gift to the holiday guests.
I have ripped it all back to shiplap on the walls and the oak (actually looks like pine where I can see grain under the black stuff you identified somewhere else on your blog.)
I repaired the rot in the pine with plywood insets which created a slight depth difference. Do I thinset the floor before adding the 1/4 plywood and then thinset the plywood before the cement board? Or just thinset the low areas on the pine and then the layer between the plywood and cement board? There is tar paper between the subfloor and the pine so do I need another vapor barrier on the floors before adding the plywood?
I’m confused and really exhausted!
If it weren’t for this website and my neighbors and the city trash haulers (I run out to tip them for picking up the bathroom debris) who are cheering me on I’d be overwhelmed.
thank you!
No need to add thinset between your wood layers. Just make sure the 1/4″ is fastened down really well with screws and install thinset between it and your backer. Other than that you’re good to go. No additional vapor barriers either.
I’m not confused – I am really exhausted, though.
Rest, elf, rest. No rush on the answer but the shiplap’s surface contains some black mold in the tub area and behind the sink.
I sprayed it with diluted clorox, let it set and then sprayed it again and scrubbed it wearing a mask and running out of the room like a banshee (this would be a place to inset one of those animated figures below but none are appropriate- btw what the hell is #8 doing?)
gratefully, eternally, grateful,
Kathy
oops, #9! Has the black mold invaded my brain?
The only thing that will absolutely kill mold is allowing it to COMPLETELY dry out. Contrary to (extremely) popular belief – bleach does not kill mold. Bleach only makes mold white. Really. The area needs to be completely scrubbed clean and allowed to dry completely to rid it of mold.
#8 is rolling his eyes, one I under-utilize given some of the questions I’m asked (not yours) and #9 is head-banging to some serious heavy metal music – something I over-utilized in my younger days.
Elf
So I am just now getting around to doing this (leaking roof more important). I have put down the plywood bought the Durock and modified thinset but how thick do I make the thin set between the plywood and Durock and to I trowel it smooth or use a notched trowel?
Thank you elf guy
Kathy
Hi Kathy,
Use a 1/4 x 1/4 notched trowel. That should fill the voids and give you a solid base.
I saw an arcticle on tile that said that vinyl tile on tile does’t work well. I am curious as to why they tell you to rough up the old floor before the adhesive, without roughing up the underside of the new tile. I would think that this was their problem. The old tile is smooth and so is the underside of the new.Will the new tile bond as well as the tile underneath if it is not roughed up. Absolutely not. How can it. Iam not a tile man but this seems like a no brainer.
Hi Gary,
The new tile may not be rough but it does have open pores made specifically for the adhesive, the face of the old tile is not made for adhesive – it’s made for durability. To allow the adhesive to adhere correctly to old tile the pores in the surface need to be open, this normally requires removing the glazed portion of the face. The body of the tile, beneath the glaze, has open pores through the body all the way to the back, just like the back of the new stuff.
Hi,
I am trying to find someone who can help me with a tile grout problem. I have searched and emailed so many people I have just about given up. I am praying someone will be able to help me.
I built a new 500 sq. ft. sunroom onto my home abut 7 years ago. I had large aprox. 18 x 18 porcelain tiles laid over 3/4″ Advantech with thinset and 1/2″ hardibacker board on top of that under the tiles. It is over a crawlspace. (original home is over a basement) My tiles have stayed down so far, but I have one entire line of grout going north to south (as you face into the room) and one line of grout going east to west near the exact center of the room that crack apart only from abut June to October and then the crack completely seals itself back off and you can’t even find it. I have discovered that at least the north south crack is located directly over a seam where the hardibacker meets. The cracks are hairline type cracks, but it is not a straight crack. It moves in different directions thoughout the crack (side,center, etc.). I am afraid small pieces will start to come out. Is there any way of repairing this. If I try some of the suggestions, like filling the hairline cracks with thin grout to go down in there, I don’t know what will happen when it starts to go back together when it gets colder. Will it pop out or what? We have installed a fan under the floor to help with any humidity which we thought might have been the problem, but that didn’t work. (We installed the fan this year before the crack showed up. Apparently that wasn’t the cause, because the crack is back.) Came back about the same time it happens every year. I know this is long, but I’m trying to give you as much info as possible. Please help me if you can. I don’t want to have to remove this entire floor if I don’t have to. It cost me a fortune. I just happen to live in the 18th poorest county in the nation, and we don’t have access to hardly anyone for anything. We sort of have to use whoever we can find to do our work, or pay so much we can’t afford it. Thanks for taking the time to read this even if you can’t help. I really appreciate any feedback I can get. PS. Just happened to do an inspection and now there are even more cracks. No tile is cracked at all. Is there any way to reinforce this floor, before I get out a jackhammer?
Thanks.
Hi Regina,
With a 500 sq.ft. room the problem isn’t necessarily your substrate or anything beneath the tile – the problem is lack of expansion joints. I’m assuming that every grout line in that room is grouted with grout? I know that sounds like a strange question but with indoor installations with direct sunlight exposure you need to have what are called expansion joints every 8 to 12 feet. An expansion, or ‘soft’ joint is simply one of the grout lines filled with flexible caulking or silicone rather than hard grout. You can read about what they are here: Soft Joints and how to utilize them here: How to install a control joint in tile.
Normal seasonal changes are causing the cracking and you likely had the tile installed sometime between October and June, yes? You’re lucky in a couple of respects, when the initial movement began it expanded out rather than contracting in and rather than popping tile or cracking random grout lines it seemed to stay with specific areas. This may be due to the particular construction points in that room, I don’t know, but you’re very lucky it did that.
All you need to do is get a grout saw (small hand tool to remove grout) and remove all the grout from those two grout lines. Get a hold of some caulk or silicone which matches your grout color (or very close) and fill those two grout lines with the flexible sealant rather than hard grout. Caulk or silicone has the ability to expand and contract without breaking the bond (micro-cracks) Most grout manufacturers make a matching caulk for their grouts. That should solve your problem and prevent a larger problem down the road with all your grout cracking and/or tile ‘tenting’ or popping.
Hope that helps.
Hi again,
There room really doesn’t get a lot of sun per se, I have thirteen windows in there but they all have blinds between the glass which are always closed. (That much sun would really run up the electric bill.) Do you still think that could be it? There are no expansion joints, it is all sanded grout (1/4 inch lines and the tile is a sort of uneven texture). But, like I said the tile hasn’t cracked at all. I also noticed that most of the cracks are occurring where the flex ducting runs under the floor for the ventilation system. It just about runs right along with them. Does any of this make any difference in your answer? Thanks so much for your help. You are the only person on this whole internet I have gotten an answer from.
By the way the tile was installed in October. You’re good.
The ducting may be the factor, but it is still due to seasonal changes. Heating and cooling systems are run in nearly the same manner every year so heating up those ducts (or cooling them down) may affect the substrate. And it still doesn’t change the answer.
Since the movement is confined to those two specific grout lines a soft-joint would solve the problem regardless of what particular aspect of the structure is causing the expansion. And whether or not is does get direct sunlight it should still have control joints, especially with what you’ve described.
THANK YOU! We will be installing control joints now. I really didn’t won’t to tear that floor up, but I’m a stickler for things done right.
We took up 2000 sf of wood flooring to replace it with 18X18 marble. We need to raise the floor up 1.5″ to install the marble so it will fit under all doorways. We are down to a concrete slab. House was built in 2005. What is the best subflooring to use for this job to avoid problems? We have had contractors recommend just cement, a mixture of sand/stone/cement, then thinset, then the marble. Do we need to put a latex primer on the current slab first? We just need some sound advice! Thank you.
Diana
Hi Diana,
The sand/cement mixture they are speaking of is known as a mud bed. That is likely the best option for your particular installation. No need for any sort of primer on the concrete. If you want a ‘bonded’ mud bed you would simply use thinset beneath the mud to adhere it to the concrete. They gave you sound advice – really.
Dear Rodger,
Thanks for replying to my question so quickly. What type of chemical is effective to scarify the surface of the concrete and cutback residue? If I don’t need to flatten the floor, will the tile adhesive stick to this residue so I can tile on top of it? or If I don’t want to deal with the glue residue, can I lay a sub floor on top of the concrete and glue residue to start with a clean surface? If so, how thick should the sub floor be and of what material should it be made and how would I attach the subfloor to the concrete with the glue residue on top of it?
Thanks for your insight,
Flora
Hi Flora,
All the chemical to remove and/or release cutback are acids – very nasty acids. And after the acid debonds the cutback from the concrete you still need to clean up the mess – acid soup. It is a very dirty, very nasty dangerous job. It is always best to mechanically scarify the surface of the concrete until the cutback is down to a dull, brown stain. There is no thinset or setting material which will stick to cutback! I know, it sucks, but that’s what it is. The cutback must be scraped or ground off the concrete before any type of setting material can ‘grab’ onto your concrete substrate.
The only ‘subfloor’ so to speak that can be installed over concrete are all adhered to the concrete itself – with thinset. Back to square one. The only other real option is a mud bed float – that would add a minimum of 3/4″ height to your floor.
Roger,
Thanks so much for the information. Since I am doing this myself, I think I will consider a floating floor.
Hi Rodger,
I would like to tile the family room floor and just removed the original tile from the 50’s. . I am left with a film of black glue residue on the concrete and was wondering if this needs to be removed or can I tile on top of it. Also, If I need to flatten the floor, can I pour thinset on top of the glue residue?
Thanks,
Flora
Hi Flora,
What you have there is known as ‘cutback’ adhesive, and it’s a pain in the ass! You will need to remove as much of that as humanly possible and make sure your concrete will absorb moisture. Just splash some water on it and see if it soaks in or beads up and sits there. If it beads up you will need to mechanically or chemically scarify the surface of the concrete in order for the thinset to bond correctly.
No, you cannot pour thinset on top of the residue. Well, you CAN, but it won’t last, so no.
Great site! Great info!
That being said… I am about to tile the kitchen floor. I have reinforced the joists and installed 3/4 tongue-n-groove properly with subfloor glue and coated screws. It is very strong, no creaking or movement. As you can see I am proud of it
But I digress, I have noticed that at the floor in one spot is out a 1/8″ to less than 1/4″. Do I need to level or can I press on? If not, do I use the leveling compound? I am very close to level; I measured over 4 feet and have a max of a 1/8″ variation. What say you?
Hey Wil,
The standards state 1/8″ variation in ten feet. Depending on what you are using for your tile substrate you will be able to compensate for it. If you are using backerboard place your thinset down and lay the backer in it. Screw down all the areas except the low spots. Let the thinset cure then install your screws into the low areas. If you are using ditra just put more thinset beneath the low areas and use a straight-edge to embed the ditra – this will keep it flat. Then let the thinset cure before you walk on it or install tile.
I am tiling a basement floor that has some dips and humps of 1/4″+. Can I grind down the high spots? I’ve heard that standard floor leveler is not ok for tile. Thanks
Hey Greg,
Yes you can grind down the high spots. SLC (self-leveling cement) is used all the time in tile installations. If used with the proper primer it is acceptable for tile.
Hi Roger,
I am tiling a bathroom floor. I have removed the vinyl floor and found that the sub floor is more than 1 1/4″ thick, is flat, and made of layers of plywood. Can I just tile over the plywood or do I need to install a 1/4″ cement board first.
Thanks,
Hey SBatson,
You still need a surface suitable for tile adhesion. This can be 1/4″ backerboard, ditra, or any of a number of products. Plywood is not suitable for tile adhesion. It can be done – but it requires a very, very specific method to be successful.
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Hello Roger, Thanks for your help. I have tinkered with the thought of installing long plank 4×24 inch wood look tile. Two things concern me.
1. the realistic look as compared to a real wood floor
2. the grout lines — how thin they can be and how to make them blend in
with the wood look
Thanks for your assistance.
Hi Carter,
As long as you get a fairly high-end (read expensive
) plank tile it looks very much like real wood. A friend of mine in Florida recently finished one up in Tampa. You can see photos and a description here. Ignore all the spam keywords – that’s how he rolls. 
I believe he used a 1/8″ grout line but the size would be dependent upon the tile you choose and the flatness of your substrate.
As long as you have an absolutely flat substrate and stagger the tiles correctly (randomly from row to row) and choose a matching grout it will look very much like a wood floor – and last a lot longer.
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.
Thank you for all your great info, I would have hated to try and do this work without it. I have another question about redoing the floor tile in my 2nd floor bathroom. I started to tear up the awesome pink tile from the 60’s and realized there must be a good inch of mortar underneath it. The great thing about the tile is they are solid as a rock, no squeaks, loose pieces or anything. THe bad thing is they are hideously pink.
Anyway, the question is can I just remove the pink tiles and tile on the existing mortar? Or do I have to tear up the entire thing to the subfloor and risk jackhammering the first floor ceiling and surrounding walls completely loose to remove the mortar? I guess I am afraid that I may never get the floor to line up with the floor in the bedroom once I do it.
Any suggestions would be greatly appreciated. Thanks again.
Hey Kinsley,
What you have there is an old-school mud deck – and they will last through a hurricane. Yes, you can just remove the tile and install right over it. If you remove any chunks you can simply fill it in with more deck mud (4 parts sand to 1 part portland cement) or just regular thinset.
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.