Proper Setting Materials for Tile

by Roger

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.

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Scott fn ritchie

Unmodified or modified, or fortified thinset in the shower? Does it make any difference if redgard is on the walls ceiling or floor? Thanks.

Reply

Ryan

I have a concrete pool wall and want to put tile on them as the top surface, so will thin set be ok submerge underwater all the time, or do I use epoxy?
Thanks,
Ryan

Reply

Roger

Hi Ryan,

Thinset is fine. Thinset under water is actually stronger than thinset under a bathroom floor.

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Ben

Hi Mr. Elf!
I’m installing my first slate floor, small project, 63 square feet. I read in the comments that you advise against sealing the back of the tile prior to setting it. This makes total sense by the way, however, why did the Lowes guy say the slate will absorb the water out of the thinset, hurting the bond – hence his reasoning for sealing the back of the tile first??? Should the steps go… 1. Lay thin set, backer board, screw, 24 hr cure, dry fit tile, thin set, lay tile, 24 hr cure, seal, grout, wash, dry, seal, seal??? :) hope that makes sense!
Cheers,
Ben

Reply

Roger

Hi Ben,

Because he has just enough information to make really bad suggestions. :D Your order is correct.

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jay

I have a wooden wall baseboard about 4 inches high where I want to apply tiles. It will have occasional moisture in is area sometimes. How should I prep that area, to apply 4 x 6 tiles on it?, its about 15 feet long. What material should I use to apply tiles?

Reply

Roger

Hi Jay,

It depends on what you mean by occasional moisture. Water splashing a little bit, or do you turn the room into a swimming pool periodically. If it’s just splashing you can just install them right to the drywall with thinset. If it’s an area that becomes submerged or sees regular water you would need to tie a waterproofing into the floor (which should also be waterproofed in that case). Kerdi on the wall tied into ditra on the floor is the most common and easiest.

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Pete M

Hi Roger,
I have a neo-angle shower with an ABS base (I think it’s ABS). I want to put small marble accent tile on the part of the base that you see outside the shower’s glass walls. I’ll scuff it, but what product for the tile? Thanks!

Reply

Roger

Hi Pete,

Epoxy setting material (expensive, but correct) or silicone (cheap, but not *technically* correct, but it’ll work fine).

Don’t tell anyone I told you that. :D

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Bert

installing travertine backsplash(2″ sq. on mesh)over very secure Fomica laminate. Will premix medium bed thinset work? Do I seal prior to grout? Do I need to grout small imperfections on stone surface or just seal?
Thanks, Bert

Reply

Roger

Hi Bert,

No, it will not work. In fact nothing will bond the mosaics to formica. It needs to be removed or covered first. Yes, seal prior to grout. You don’t need to grout the small pits, you can just seal them if you want.

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Sheree Adams

Hello,
I have a question about putting stone tiles (with mess backing) on metal surroundings of a wood burning fire place? When I removed the old solid tiles, it looked as if they had been glued up there (Liquid Nails). I have been reading and researching trying to make my mind up. I have been told so many different things that I am really confussed. Please help?

Reply

Roger

Hi Sheree,

There are only two things that I will use on a metal fireplace – epoxy and laticrete 255. With both you want to sand the paint down to the bare metal. I wouldn’t guarantee that anything else would last. It may, I just wouldn’t do it, I know those two things work.

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bill j

Mr Elf
I’ve done a few projects with porcelain and have always been satisfied with the results. But recently, I laid 1′ by 2′ black slate in a bathroom over ‘medium bed’ thinset mortar. Following the advice of the tile ‘expert’ at HD
I applied ‘Aqua Mix Sealer’s Choice’ to both sides of the slate before installing it on 1/2″ backer board. During the days that followed I discovered that the bond had failed on a number of tiles. Now with each day that passes, another piece of slate comes loose. Where did I go wrong?

Reply

Roger

Hi Bill,

You put sealer on the back of the tile. This closes the pores in the stone (it’s made to do that) which the cement particles need to be able to grab and grip the tile. Go back to hd and find a manager. Explain to them that they need to replace your stone because they instructed you to prep your stone in a manner which did not allow the thinset to bond to it.

Jackasses. All of them.

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Joe Hill

Hi Mr Elf

I have made a tub surround that runs level with the top of the bath tub and want to run the tile over the top of the tub (i have removed the lip) so it looks like a drop-in/under-mounted bath. The tub is fiberglass but well supported all the way round and underneath with timber framework. I am planning to use Laticrete Platinum 254 Epoxy and Spectra Lock grout. Do you think that is the right way to go or should I go for some kind of silicone based adhesive like Novogard?

Thanks in advance.

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Roger

Hi Joe,

Is the tub fiberglass or acrylic? They have different properties. Provided the tub is scuffed up so it no longer has a shiny surface then it would work with acrylic. I honestly don’t know if it will work with the fiberglass.

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Francesca

Hi,
I had a shower installed 2 months ago and the guy used mastic on the walls and the floor. After a month the floor tiles started to loosen and Come up. I am now having someone else fix it although he has agreed to do the tear out as he wants to “save” the tiles! How hard is it to remove this mastic from the back of the tiles? They are 12″ x 24″ Porcelain. He only waited 1 day to grout So I’m thinking it didn’t even dry all the way. He also refuses to pay for the re-install cause he wants to do it himself. I Say no way cause there are numerous other problems like lipage yada yada. . .

Reply

Roger

Hi Francesca,

The good thing (only thing) about mastic being water-soluble is that the tile can be soaked and the mastic removed. They can be saved, but I would make damn sure he gets all the mastic off of them before they are reinstalled. I wouldn’t let him install them either!

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Francesca

Thanks Roger!
This is gonna be a mess isn’t it?? do you think I should be entitled to have him pay for the new guy to reinstall since he messed up in the first place and obviously doesn’t know how to lay tile which he told me he could.

Reply

Roger

Yes, I do. Going about doing that, however, will depend greatly on your local codes and laws.

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Gary F. Logan

Hey Mr. Expert,
(No smarky-remarky!) I have tons of that smooth stream stone that I would like to apply to a large area over painted plywood. They used some of that floor paint with the grit in it which is very annoying when you are barefoot. They put 3/4″ plywood down first which seems pretty solid. Do I have to remove all of the latex w/sand grit from the surface before setting the 1-2″ stones? And if so…how? Much appreciated! Gary

Reply

Roger

Hi Gary,

You can’t install stone to bare plywood anyway. Get some cement backerboard (1/4″ is fine), put down a layer of thinset, lay the backer into it and screw it down. Then install your stone right to it.

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Kevin Chisholm

Aloha Big Kahuna Elf, I have spent so many hours online and and phone with tile guys I know (and some I don’t or at least shouldn’t), My question is…Im building a 14 x22 second floor porch/roof over and exterior kitchen. My concern is with weight and the height of the door that leads out onto the porch that we are tearing down (only 4 feet wide) and extending it to the 14 feet mentioned above. Point is we can’t build up the deck because we can raise the door and if we lower the deck/roof we loose any headroom below. SO…..I was told that 3/4 plywood over 12inch on center joist and the apple hydrostop as the waterproof “roof” part of the job and then tile right over the top of the hydrostop…Is this possible??? what thin set should be used???? (I live on an island with only 1 home depot and 1 specialty tile place to order. Sorry so long…in hawaii we call that “Talk story” Mahalo ( Love your site)

Reply

Roger

Hey Kevin,

Never heard of hydrostop and from what I can find online it doesn’t look like it’s supposed to be tiled over. You can go with 3/4″ over 12 oc joists, 1/4″ hardi over that with thinset beneath it, hydroban or redgard over that then tile. That should work just fine. Proper flashing and all that, too, but you already knew that.

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Bob R.

Hi Roger,
Is it OK to grout the next day after setting all the shower tile and then seal it the next da ?
I’m using Versabond Thin set on Mapie Aquadefense covered concrete BB with 9 x 12 porcelain field tiles with 1/8″ sanded grout joints. Then want to seal it next day with your recommended Miracle 511 Impregnator Sealer. I’m trying to make a July 5 finish / turnover date for a sister’s remodel job, but if you say drying/curing time is needed between these steps, then I will just have to be late.
Also, when is it safe to drill holes in new tile job for safety hand rail, shower hose spray slide rail, Handicapped folding seat, and sliding shower door w/ frameless glass?
Thanks so much for this forum and your time to answer ALL the questions.

Reply

Bob R.

Oh, I forgot to say that ALL mounting holes for the things I’m installing on tiled shower wall will be hitting 2 x 6 blocking behind the cc bboard.

Reply

Roger

Oh, same answer. :D

Reply

Roger

Hi Bob,

Yes, it’s fine to grout the next day. Yes, it’s fine to seal the day after that. You can drill holes after the grout is cured (same day you seal).

Reply

Paul

Hi Roger-

This is similar to the above question but it is nice to have reassurance as I’ve already had 3 dogs and a hampster explode this year.

I am putting down 1′ x 2′ gauged slate over ditra and have about 2/3 of the floor finished using Bostik Ditra-set and a 1/2″x1/2″ trowel. Problem is I’m out of ditra set and he ONLY store driving distance from me is out and would have any for at least a couple weeks. I’ve also looked at all the options for unmodified medium bed mortars and none are available locally.

So, if I do use a modified medium-bed such as Custom’s Marble, Granite between the ditra and slate will I have committed a major sin? My wife and I would prefer not to wait another few weeks without a floor- but will do so if that is the only option.

Thanks for any advice! Paul

Reply

Roger

Hi Paul,

According to schluter yes, it would be a major sin. Luckily schluter is not a church. Use whatever you have available, your dog (and hamsters) will be fine. :D

Reply

Kurt

Roger,

In Scarlet’s reply, you recommended Laticrete 125 for wood-looking tiles on a cement slab. I can’t find any local distributors for Laticrete products, but I was able to find FlexBond Crack Prevention Mortar (50lb fortified thin-set). Would that work just as well? I also have access to Mapei products, if they have a similar product.

Also, I am tiling a large area with the long, narrow wood-look tile. There is a sunken area in one part of the area that drops down about four inches. Do you have any brilliant suggestions :idea: for making the “step down” edge a little more visible, so that we don’t have house guests flopping down on their faces and suing us?

Reply

Roger

Hi Kurt,

Yes, the flexbond will work just as well, better, actually. If you are running the pattern perpendicular to the step you can put a row along it opposite of the main tile. If it is running the same way you may want to find a border tile or something to run across the front of the step. Or install an led light strip into the tile on the step.

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Dave

Sigh. I just want to put natural slate tile (12x12s) on my properly prepared kitchen floor. What mortar do I use? There are entirely too many options.

Reply

Roger

Hi Dave,

If you are using ditra use laticrete 317, if you are using cement backerboard use laticrete 253, Mapei ultraflex 2 or versabond. If your floor is NOT flat or your slate is not gauged, use a medium bed mortar like laticrete 4xlt or custom’s tile and marble mortar.

Reply

Tom

I am getting ready to tile my tub surround using 3 x 5 glass tile. I am at a complete loss as to what material to use other than “never use mastic on glass tile”. PLEASE HELP ME! :-?

Reply

Roger

Hi Tom,

In my opinion your best option is cement backerboard with hydroban over it, set the glass with Laticrete Glass tile adhesive (it’s a medium-bed mortar). You should be perfect with that combination.

Reply

Scarlet

Hi,
I am having 7″ x 20″ wood look tile (not rectified) installed in a staggered pattern over concrete slab in several rooms that flow into each other (1000 sq ft overall). There are a few minor cracks in the slab that i want to avoid a future transfer through to the tile. A few questions:
1) I want 1/16″ tonal grout with Spectralock Pro Premium. Will this width work or do I need to go wider? (Thanks for the tutorial on how to break up the commercial unit size of the Spectralock :) )
2) Should I put down some Red Guard membrane or similar to minimize the crack issue?
3) I read about the Laticrete 125 crack prevention and sound isolation thinset. Does this work? Is it worth the extra cost for minor cracks? Will it flex under heavy weight (like the leg of a chair with a 300 lb guy on it) and crack a long format tile?
What thinset and trowel size do you think will be best for this project?

Thanks for your help :)
Scarlet

Reply

Roger

Hi Scarlet,

1. Spectralock will allow that width, I doubt your tiles will. You should probably have at least 1/8″ grout lines with that size tile.
2. Yes, redgard is a good crack suppression membrane. It needs to be a minimum of three inches on each side of the crack, the wider the better.
3. Yes, it does work. It is worth it not only for that, but future cracks as well if you aren’t using any other type of membrane beneath your tile. No, it will not flex nor crack a tile.

Many different types of thinset are just fine for that. The 125 would be a very good choice. Trowel size is whatever gives you the correct coverage.

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Scarlet

Thanks for the info.
I will do 1/8″ inch grouts.
The 125 is quite pricey. Can I use it over the cracked areas and then use a less costly thinset in the other areas? Like 253 gold?
Thanks, Scarlet

Reply

Roger

Use it for the whole thing or use a crack suppression membrane over the cracks and the 253 gold. The 125 is perfect for installations where it is cracked as well as compensating for cracks that may appear later. It does no good to only use it over existing cracks if your slab develops other cracking in a different area.

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Joe P

Hi,

I have a few different scenarios of tile installations I’m doing in my bathroom and I’ve got a few questions for ya.

Background info:

I’m planning to use RedGard over Hardibacker in the shower. I need to fill cbu gaps with thinset/fibertape, redgard over it, then thinset and tile over that. I’m laying 12×12 travertine on the walls. For the shower floor, I made a sloped cement floor which will need redgard as well and then thinset for 2×2 travertine tile. Outside of the shower I plan to use the 1/8″ ditra membrane (over the reinforced ply floor) with 18×18 travertine tiles (might even cut them in half).

1. Is there a certain type of thinset I should be using specific to RedGard or travertine within the shower? I’m assuming a standard modified thinset would work here but I know there exists some natural stone specific thinset. Do I need that for walls and floor?
2. My current understanding is that on the Ditra I should be able to use unmodified thinset and I can pretty much figure out what to get based on your Unmodified Thinset guide (http://floorelf.com/unmodified-thinsets-a-users-guide). The only problem with that is the Lowes I have around here doesn’t match what your guide was suggesting for Mapei. They must have renamed everything (or I’m blind).
3. Maybe this is a dumb question but I did not see any “corner reinforcement tape” near the RedGard at the big box store. Is this just standard fiberglass material? Any idea where I can get this?
4. Unrelated question: When I did my sloped cement, I didn’t get the slope perfect. At the top it’s a little less than 1/4″ per foot and at the middle it’s a little more than 1/4″ per foot. Is it really worth ripping it out or will the world keep turning?

Reply

Roger

Hi Joe,

1. Any good modified thinset will work. Stone specific mortars are medium-bed mortars. They work well also, especially if you have larger format stone (like your travertine).

2. If you tell me what they’ve renamed them I can tell you which to get. :D

3. In the tile section there should be alkali resistant fiberglass mesh tape, it’s normally used for taping backer boards. You can use it. Regular drywall mesh tape is not alkali-resistant and may degrade over time.

4. The world is safe. :D Any rectangular shower with a level perimeter will not have a consistent slope. And they said I’d never use geometry. :D

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Joe P

Alrighty, Elf Dude…

I picked up some Versabond to adhere the Ditra to my plywood floor (and also to bond the gaps between sheets of CBU on the walls). I picked up some Custom MARBLE, GRANITE & TRAVERTINE PREMIUM MEDIUM BED MORTAR for the shower walls and floor. Now my only question is what to use between Ditra and tile. Here are a few of the options I saw at HD and Lowes (I know some of them aren’t really options):

– CustomBlend standard thinset mortar (http://i.imgur.com/olAFNQQ.jpg)
– Custom MARBLE, GRANITE & TRAVERTINE PREMIUM MEDIUM BED MORTAR (http://i.imgur.com/fQL9L3J.jpg)
– Mapei Floor Tile Mortar (http://i.imgur.com/xgAYX7Z.jpg)
– Mapei Large Floor Tile Mortar (http://i.imgur.com/IOmIz3L.jpg)
– Mapei Floor and Wall Tile Mortar (http://i.imgur.com/RQ5uGLh.jpg)

Are any of those an option for putting between Ditra and 18×18 travertine?

I’m glad I’m doing this project myself because I won’t feel nearly as bad paying someone else to do similar projects in the future ;)

Reply

Joe P

I also have Menards not too far away that I can check (again). Last time I went there I didn’t see anything from your unmodified list.

Reply

Roger

Hey Joe,

Mapei floor tile mortar is close to the kerabond – it will work just fine.

Reply

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