There are three basic materials used to set tile.
- Mastic
- Thinset Mortar
- Epoxy
For each installation there is a specific material you should be using. Before you start any tile installation you should ensure that the material you choose is suitable for that application.
Mastic
Mastic is a latex or solvent based adhesive that cures by evaporation. It is sold in airtight containers (buckets) and requires no mixing. It is ready to use immediately. It is suitable only for non-wet applications.
Mastic should never be used for showers or floors! Ever! When mastic gets wet the water will re-emulsify the adhesive base. This means that mastic turns to goo when it gets wet. Goo will not keep your tiles on the wall. Every one of the failed showers that I’ve ever replaced were installed with mastic.
With that said typed, mastic does have its place. It is “stickier” than thinset mortar which is why some prefer to use it – for everything. It should only be used in non-wet areas such as a backsplash, wainscot, or fireplace. An area that is not consistently exposed to water or moisture. It should also only be used on tiles smaller than 6 inches square.
Think about it like this: mastic is stored in a bucket with a lid on it. This keeps it from being exposed to air which would cause it to cure (dry). If you spread it on your wall and place a 12 X 12 inch tile on it, that’s just like putting the lid back on the bucket. It will never fully cure. If any moisture gets behind that tile with the mastic it will eventually re-emulsify and lose adhesion. That means is that your tile is going to fall off the wall.
There is also a product called “premixed thinset adhesive”. This product is pushed as a suitable material with which to set tile – it is not. It is only mastic with sand added to it. While sand does help materials from shrinking as it sets, it does not make mastic suitable for showers or floors.
Thinset Mortar
Thinset mortar is what you need to use for shower walls and floors of any type. It is sold in bags and needs to be mixed with water. Sound simple? It is. Referred to as thinset, mud, mortar, or a number of other things, it is a combination of sand, portland cement, lime, and other stuff that makes it the preferred setting material for elves everywhere.
When mixed properly (read the directions, no, really, read the directions) it is stable, not compromised by water or moisture, and rock solid. Thinset must be mixed with water, allowed to slake, then remixed before use. Slaking refers to letting it set for a specific amount of time to allow the chemicals to interact and become workable.
Thinset cures through a chemical process, not by evaporation. Air is not required for it to set. It will cure in the bottom of a bucket of water, really. This means that no matter the density or type of tile you use it for, it will fully cure. No worries there. The tile will stay where you put it.
Unlike mastic, thinset will not be compromised by water or moisture. If it gets wets the thinset will remain cured and will not be reactivated. It’s similar to your driveway. The concrete on your driveway was mixed with water but it doesn’t turn to mush when it rains. It’s the same stuff.
Thinset mortar will be the correct setting material for nearly every application.
Epoxy
Epoxy is a chemical based glue that cures through chemical interaction. It is almost bulletproof and not user-friendly. To be frank, it’s a pain in the ass. It is usually a two or three part product which, when mixed together, form a very stiff, very thick putty-like substance. When cured it becomes a permanant part of whatever is attached to it. That’s great on the back of the tile, not so much if you get it on the front. Use with care, it is nearly impossible to get off of anything once it’s set.
There are not many applications which require the use of epoxy setting materials. Certain exterior applications need it, swimming pools, certain types of stone and glass tiles. While epoxy can be used for any application, only specific jobs actually require it. It’s expensive. I mean really expensive. If you don’t need to use it, don’t.
If you are unsure whether or not your product or application requires epoxy, just check the manufacturer’s recommendations. If it is required, they will make sure you know about it. You can also ask me, just leave a question in the comments. I’ll reply, I’m a fairly sociable guy when I’m not crawling around on a floor.
Which to use
The general rule of thumb is to use thinset mortar. Unless your specific application requires epoxy, thinset can be used. Anywhere you can use mastic you can use thinset instead. It is more durable, water resistant, and cheaper than mastic anyway. As far as I’m concerned, the only thing mastic is good for is a free bucket.
My ceramic tile in my kitchen and foyer are in good shape but outdated (23 years old). They were laid on the sub floor with metal mesh and thinset. What do I nee to do to replace them? I have taken up two rows under the stove. The thinset seems to be coming up without problems, metal lath is another story! How do I get it up. Do I need to put down Cement backer board before I lay porcelain tiles? What if my sub floor is not level?
Thanks in advance. PS I’m retired so I need to save money!!!!
Hi Cheryl,
Take up all the tile and the lath is likely nailed to the subfloor. Either pry out the nails or grab the lath with pliers and yank it out. You need a proper substrate for your tile, backer is the least costly. (You need thinset beneath it).
Elf,
About ready to install a 12x 12 mosaic backsplash in my kitchen over primed drywall. I plan on using thinset.
1. Do I need modified or unmodified?
2. The mosaic has some glass pieces, do I comb the thinset with a v-notch trowel? or do I use the smooth edge, I’m worried about seeing the the lines from troweling the thinset through the glass tiles.
Hi Norm,
1. Either will work, modified would be better.
2. Comb it first, then knock down the ridges with the flat side of the trowel. This will leave the proper amount of thinset on the wall without having the lines behind the glass.
Roger
One more question..what size trowel should I use.
Have a great thanksgiving
1/4″ v-notch trowel.
Hello FloorElf!
I have prepared a bathroom floor with two, built up, layers of Sakrete Sand and Bedding Mix that was leveled over a very uneven concrete slab. I would like to then use 1/4 to 3/8″ of thinset over this to secure my travertine at the proper height.
Question – how long do I need to let the Sakrete cure? Is there a specific window when best: i.e. after 24 hours but then not until after 28 days…or some such muck?
Thank you much!
Hi Nathan,
Anytime after 24 hours, up to and including 25 years.
Hi Elf,a quick question> on laying 12 inch porceline floor tiles down,…do i really need a grout line or can i lay the tile tight,and grout what little line there is?
Yes, you need grout lines. Tile without grout
I am planning to put foot square marble tiles. I plan to put hardie board around the fireplace and glue tiles over the board with thinset. What kind of thinset should I use? Thanks
Hi Gil,
Any good modified thinset will work. At home depot you can get versabond, that’ll work fine.
We took the advice of the Home Depot floor “specialist” and bought type 1 mastic to lay 12 inch tiles on our kitchen floor. Not until piecing the edges did we read “for floor tiles up to 8 inches”… Jumped on the web and found you. The 172 tiles are ready for grout. Can you give us advice? Hoping we can seal the grout to keep water out.
Hi Marion,
Water migration and re-emulsification are not the only problems with mastic. The biggest issue in your installation is lack of compressive strength. Mastic has very, very little and you have it in a high traffic area. It is not going to last, it simply can not handle the load and traffic a kitchen (or any floor, for that matter) will receive.
Roger:
I’m replacing several slate tiles (12×12) on an outdoor entranceway patio. It’s partially covered but does have some exposure to the elements. The surface is concrete with a bit of leveler in places. What kind of adhesive should I use?
Thanks so much!
Hi Tom,
A good modified thinset will work fine. Ultraflex 3 and Laticrete 254 are two very good ones, there are a lot.
Hey there,
that’s me at the moment lol
I bought that CRAP!!! Well we are not happy with it we did what the so call directions told us to do and hell we have to hold one damn tile up for almost an hour before we can move onto another one. I guess my question is, is there some other way to us this CRAP or do we need to take it back and get something better that we don’t have to hold forever?
My wife and I are remodeling the kitchen, and we are to the backsplash. well its on the wall and we found a great deal on some 12X24 porcelain tile and they told us that we needed some type 1 mastic to put it up on the wall it will hold the best so without me knowing any better
Thanks for your speedy reply.. only got 2 peaces up and got mad and stopped lol waiting on your advise. lol
Hi Charles,
You should have thinset for tile that large. I don’t, however, understand why you’re holding them there until you move onto the next. Do you not have them on the counter or supported from beneath while they cure?
Thanks
Yes it is 13 inches form top of counter top to bottom of cabinet and my wife thought since the cabinets were more level that it would look better to put them up against it so we can see a little bit of the wall color under the tile and above the counter top.
You say to use thinset is that the mortar you are describing above and what is the name I need to look for if i was to go to HD?
Thank you
Versabond will work fine, just cut some pieces of wood or something to hold it up there while it cures. Prop the tiles up from the bottom, you don’t need to hold them there.
Right on sound good, Thanks so much
now time to set and watch it dry 
Hi Elf,I am going to tile the floors,in my moms small kitchen, (looks like a sidewalk basically with counters on each side) it’s a straight run that goes through a door out into a small laundry room. would ceramic tile be ok or should i use porcelin tile.Some one said if they ever dropped a can of food on it it would break or chip it if i used ceramic. Thanks for the advise on the thinset,(they tryed to get me to buy a 32.00 bucket of mastic) .
Hey Michael,
Porcelain can chip if something is dropped on it as well, just not as easily as ceramic. Porcelain is much more dense (typically) than ceramic. Porcelain is normally always a better option in heavily trafficked areas such as a kitchen and laundry room. It’s more durable, but it isn’t bulletproof.
Great ,thanks again for getting back so soon to me,another question if i might ask is what size spacer is recommended 1/4? and should i tile all the way under the fridge and oven.Seems like when we first moved in it didnt go all the way under them.
1/4″ is huge, I normally use 1/8″ on floors. Yes, the tile should run under the fridge and stove both.
Thanks Elf,for your rapid response,another question if I may,my moms kitchen floor is only about 3 foot wide .It’s like a sidewalk about 6 or 7 feet long and goes thru a door out into the laundry room which is 7×8 ft. If i’m sitting at the table in the dining room looking straight down the kitchen,should i have a full tile in the center running straight thru and on out into the laundry room ,or should it be a grout line in the center.also, i was using 12×12 porceline tile. should i go to a bigger size or will it make it look smaller? thanks for your advise.
Hi Michael,
If you can have a tile centered down it and the space on each side is less than a full tile go that route. If it’s bigger on each side then one tile then put a grout line down the middle. A bigger size will not make it look smaller, it actually makes it look bigger. I know that sounds counter-intuitive, but it’s true.
Hi,
Laticrete says “about” 5.5 qts water for 50# of 254 modified thinset. That seems a bit thick post mixing/slaking. Stiffer than my pancake batter, anyway. They don’t mention a consistency target other than “smooth.” It has to hold the ridges, of course. How much more water can I START with and not compromise the adhesion/strength? E.g., would enough water to make a noticeable difference be too much? What do YOU do?
Thanks mate!
You can mix it to a pancake batter consistency without losing considerable strength. The normal mix is more like peanut butter – the creamy, not the chunky.
Hi Roger,
Thanks. Another question. Does dried Ardex feather finish need to be dampened prior to the 254 thinset application?
I really appreciate the help!
Hi Keith,
Not necessarily, but it certainly doesn’t hurt.
Just finished with shower tile project (with several inquiries to your site: thank you). I was cleaning up some of ditraset unmodified thinkset that had fallen outside the shower on the sub floor. I noticed if I wetted the thinset, I could scrub it away. Is that normal? Please say yes and explain how this won’t be a problem.
Hi Joe,
It is normal since it just dropped there. That’s why you need to burn it into the substrate and the back of your tile, it gets a complete grab.
Hello. My dh installed italian ceramic in our kitchen/hallway. The subfloor and a slab of hardi backerboard. Mud and the tiles. He did a good job. Home is a double wide modular (retirement) . About a year later, the grout started to crumble. Especially in the midline off the building, where the two halves join. Of course the tiles had to start popping out. Only in the midline. Would epoxy adhesive and grout help. I predict that I wil be grinding mud off the back of these tiles…btw, they were leftovers from a friends tiles business …aka free.
TIA SusyQ
Hi Suzy,
Most modulars have nowhere near the deflection ratio needed to support a tile installation, especially between the two halves. I’m guessing the subfloor is particle board rather than regular plywood. Particle board is not very supportive at all and has no business beneath a tile installation. The only way to get tile to last there is to have a minimum of a double layer of plywood totaling 1 1/4″ with a proper substrate above the – backerboard works, but a product like ditra is better.
ELF-
Retiling my shower. Gutted to cinder block wall. I re-did studs, insulated with no vapor barrier and am ready to apply shower surround. I intend to use Dens Shield vice hardiboard–lighter for me to work with.
1. when do you use unmodified vs modified thinset?
2. What process do you recommend to seal seams in shower? I think you recommend fiber tape with thinset (unmod vs mod?) with redgard or similar over whole shower
3. What thinset do i use for porcelien field tile? mod vs unmod
4. what thinset do i use for the glass mosaic? mod vs unmod
5. what thinset do i use for the floor?
6. Where the dens shield transitions to 1/2 sheetrock outside of shower do i use the same seam sill technique as in shower?
7. Verfifying the dens shield can be primed and painted?
thanks much!
Hi Adele,
1. You only use unmodified with schluter products. It is used in some specialty applications, none of which would be in a shower without kerdi.
2. That is correct, tape and thinset (whichever you’re using, in this case modified) every seam and change of plane.
3-5 Modified.
6. Yes. Outside the shower you can also use regular drywall mud, but thinset is still better.
7. Yes.
Dear Elf,
I have a fireplace project that I’ve been trying to get back to and I have some questions before I start….again. I have 1/2″ hardibacker up around the fireplace as a platform for manufactured ledge stone. This past summer I attempted to put a scratch coat up directly to the hardibacker. I prepped the Hardibacker by vacuuming any dust off of it and wetting it, but the thin-set mortar (specifically for veneer stone) did not want to stick to the wetted hardibacker. Everyone I’ve spoken to so far has said mortar should stick directly to the hardibacker but it doesn’t seem to want to.
In places where it did stick, the mortar was crumbly as if it never cured thoroughly. I was going to try it again this weekend, with more attention to wetting down the hardibacker and possibly reducing the amount of sand in the mix (directions say 1 to 1). After reading the information on “Proper Setting Materials for Tile”, I was wondering if I might be better off trying mastic? Any thoughts you might have would be greatly appreciated.
Hi Jeff,
Sorry for the delay, been out of town at the new Schluter facility all week.
It sounds like the mortar you have is not ‘thinset’ mortar, but simply mortar for stone veneers, which is different. It is basically the ‘grout’ for your stone, not the bonding product. Regular thinset will work. With natural stone, even veneers, you don’t want to use mastic.
Hey Roger,
A few questions..
1) I putting 12×24 porcelain tile on my shower walls up to the ceiling, but I have a band of glass mosaic going in at 4′ from the floor. The mosaic is 1x2x4. Very similar to this picture you have on your site, the glass tile is just more uniform: http://floorelf.com/wp-content/uploads/2013/08/IMG_3708.jpg
I’ll have Kerdi on all the walls and I can get Bostik DitraSet (unmodified) from my local tile retailer for a good price. I can also get Laticrete 253 (modified) from another. I’m really not sure which to use because of the glass. I’ve been working on this bathroom for months so the appeal of using a fast setting unmodified for everything is nice. Do I need to use modified on the glass? If so how long do I need to let it dry before I grout? I’m using SpectraLock epoxy grout.
2) I’m not going to tile the ceiling, but are there any options other than green board and paint to provide better moisture resistance? My ceilings are 8′, and I’ll have glass exterior walls up to 7′ and a good fan in the bathroom. I do have a pod light and a rain shower head coming out of the ceiling though, so I’m concerned that over time it may become an issue.
Thanks!
Hi Jeremy,
Sorry for the delay, been out of town at the new Schluter facility all week.
1. You need to contact the glass manufacturer for that specific question. You can use the modified on just the glass, it will cure fine behind that. I probably wouldn’t use it on those large format porcelains, though. Modified may work, but it may also take up to 60 days to fully cure.
2. Provided you use the correct paint (made for use in wet applications like shower ceilings) then it won’t be a problem. If you want to you can always put cement board or denshield on the ceiling, both are water stable and the denshield is waterproof. Both can be painted if you prime them.
Does this sound right, kitchen counter-top, two 1/2 inch pieces to make 1 inch of plywood, hardy backer, fiberglass tape for the seams, thin-set. ceramic tile.
Hi Tyco,
Yup.
Shortest. Answer. Ever.
Tub surround has been prepared with redgard and will be using subway tile. Should I use regular Laticrete 272 or 317 or modified thinset? Thanks in advance
Hi Starr,
With redgard you want to use a modified thinset.
On a tile redi shower pan can I use thin set mortar or does it have to be epoxy.
Hi Toby,
It has to be the epoxy, thinset will only bond until you put pressure on the tiles, then it’ll pop right off.
Cool thanks for the info but one more thing I am going to use the epoxy for the floor can I use thinset for the walls.
Yes, you can use thinset to install your wall tile.
Hello Kris,
I just recently had 12″ X 12″ Marble floor tiles installed in a second floor bathroom. Three weeks later two hairline cracks have appeared. One is just shy of 5′ long and the other is 3′. They run perpendicular to each other. I cannot hear any hollow spots, nor feel any floor bounce–I am at a loss! (and so was my tile setter who seems to have now disappeared)
The same floor was previously tiled with ceramic tiles over 1/2″ tile backer, and I never saw even a grout crack. That was all removed and the 3/4″ subfloor had been checked for any give (screwed where necessary). Then a mortar bed with mesh mat was laid over the subfloor and tiles were set with thin set. And voila! cracks!
I cannot figure what went wrong. Any thoughts would be great. Thanks!
Hi Josh,
Unless your mesh mat and mortar bed were AT LEAST 3/4″ thick (ideally 1 1/4″) and it was made with actual deck mud – sand and portland, then it isn’t a mortar bed. What I’m worried about is a technique called a jersey mud job (among others) where metal lath is bonded to the subfloor and filled with thinset mortar, then tile installed over it. They don’t work, they fail. A lot.
Is that what you have? Or do you actually have a real mud bed?
i am trying to tile plank like tiles (6×28) over an epoxy coated concrete slab. Do i need to use an epoxy thinset or can i use something like flexbbond or ultraflex 3?
Hi Tod,
You need to remove the epoxy coating. Setting it with epoxy may work, but there are no guarantees. The only definite solution is to remove the epoxy.
I am looking at using epoxy on my shower floor b/c the drain is set in concrete and its to low. What product do you recommend for this purpose?
Thank you
Mark
Hi Mark,
If you mean epoxy setting material then I prefer Latapoxy 310 from Laticrete. However, I don’t understand the part about the drain being too low. Does that mean you plan on using epoxy setting material rather than a waterproofing membrane? Because that won’t work, you need a membrane of some sort there.
I already have redgard on the floor the walls and around the drain. Because the drain is set so low I am setting pebble tile with epoxy to compensate for added height that I would get with regular thinset.
Oh, then yes, that will work.
Hello FloorElf! First, please accept my sincere thanks for all of the mistakes you have kept us from making! Some things seem so simple when you point them out (magnets to hold on the removable panel for tub access). You were invaluable when doing our niches. Our duckys fit very nicely now (as do our beers!).
We are doing our bathroom. New construction. We are tiling the front wall which is about 10 feet from the shower and we have decent fans. However, the front wall is where our sinks will be. We are putting China Black marble up, 12 x 12 pieces. Others have told us we must use mastic solely because it’s marble but if I’m reading this article correctly (Proper Setting Materials For Tile) then you are saying we should use thinset? We do not want to ever have to redo this room but we also don’t want to ruin the marble. Thank you for any advice!
Hi Kris,
You NEVER want to use mastic with marble. Marble is a porous rock and the oils in mastic can actually wick through and stain the face of the marble – it’ll look like you poured cooking oil on it. You need to use thinset, it’s stable once cured and the only liquid ever in it is water. With your marble you can use gray or white, with lighter marbles and stones you should use white.
Thank you so much for taking the time to respond. What you are saying makes perfect sense. The only reason we even questioned what we were doing was because everyone else said mastic, which, the more we learned, seemed wrong. Thank you for the assistance! We’ll be working on this wall tomorrow!
Elf, can I use thinset to adhere silestone or caesarstone to Kerdi membrane, or what is the preferred adhesive?
Thanks
Hi David,
I already answered your question – yes, unmodified thinset will work fine. If you click on the link at the bottom of the page that says ‘previous comments’ you’re right at the top. I get over 40 questions every day, the page has to recycle at some point.
ELF,
Redoing a shower and receiving bids on using a thin set mortar or plaster and wire mesh. Placing a Calcutta Marble do you have a recommendation for one vs. the other. Thin set mortar pricing appears to be a better price, live in CA is earthquakes an issue?
Hi Brooks,
I don’t really understand your choices. Plaster and wire mesh are not a proper substrate for tile, nor is thinset mortar a substrate, it’s used to bond tiles to your chosen substrate. The absolute best you can get is a mud shower, that consists of wire mesh and wall mud (not plaster). If that’s an option I’d go that route. If your other option is cement backerboard that is also a good option. Any properly constructed shower would be a good option.
Hi Elf. I am planning to redo a shower stall using the Kerdi shower membrane system. I was going to frame the door opening and threshold with Caesarstone. Can I use unmodified thinset to adhere the Caesarstone to the Kerdi membrane, or is there a preferred adhesive?
Thanks
Hey David,
Unmodified will bond it just fine.