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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david

I have removed some OLD loose asphalt tile from a concrete slab entry hall. It was glued down with black gooey adhesive. I want to replace it with slate. I have purchased thinset mortar, but the instructions warn against laying it over mastics. My second choice would be porcelain tile if it could be laid over the old mastic with new mastic, but I read above that it also needs to be laid with thinset. I considered gluing HardieBacker down first and then laying the slate using thinset, but HardieBacker is not recommended over concrete. Am I doomed to laying vinyl instead? Are there “floating” floors that are moisture resistant?

I appreciate your guidance.

Reply

Roger

Hi David,

If your floor will soak in moisture (splash some water on it, if it is sucked into the floor within about thirty seconds) then you will be fine using straight thinset. If not you can use a primer over it like mapei eco prim grip, then use thinset over it.

Reply

Joanne

I bought epoxy to repair leaks in the grout of my pool tiles. In preparing to apply it I loosened up the tile. Can I use the epoxy on the back of the tile that came off to reset it?

Reply

Roger

Hi Joanne,

Yes.

Reply

Diane E.

I would like to put tile over a mdf cabinet door. Since mdf is not very strong should I use a french cleat to hold the tile on or can I just use an adhesive or both :bonk: ?

Reply

Roger

Hi Diane,

You should not put tile over mdf. I really can’t tell you how to do something that should not be done. Sorry. :D

Reply

BillyD

Just to add another point the surface of the table is about 1/2 to 3/4 chopper gun fiberglass its not just a thin sheet of fiberglass. But yet not a solid as a boat where layers of mesh would be tightly pressed together.

Reply

BillyD

Roger, I have a tumbled marble mosaic project over an existing fiberglass table 54″ diameter. I have inverted the table and am using the underside as a kind of pan to hold the tile. The underside is fairly ridged and kinda rough fiberglass mattind texture. I have thoroughly cleaned and sanded over it and am perplexed about what thin-set or bedding adhesive I should use for the mosaic tiles. I also would appreciate your advise on grout too. This is an outside patio table completely exposed to the South Florida sunlight.

Reply

Roger

Hi BillyD,

I would use an epoxy setting material.

Reply

belinda

Stupid me thought it would be a good idea to embed small (1-2 inch) in thinset over a fiberglass shower bottom(liquid fiberglass put down by professional, not me!!!! then I covered the top with an epoxy acrylic.(I know, stupid) now the epoxy/acrylic is discoloring….my question is, should I try to remove it, most likely damaging the fiberglass barrier, or smooth it(grind it down) as best I can and use thinset to tile over it(obviously will have some issues re-installing the drain) what to do, what to do?????

Reply

Roger

Hi Belinda,

Is it epoxy or acrylic? Two completely different things. Tile over tile would likely be your best solution, you can google ‘shower drain extender’ to deal with the drain issue.

Reply

Cindy

Hi Roger-
What (if any) is the difference between thinset and medium bed mortar. I have read medium bed mortar is what you need for large tile, is that right? I am planning to lay 12″ x 24″ porcelain on concrete slab – which do I use? Also, how do I need to treat small cracks – will RedGard do or do I need to use mesh tape with thinset?
Thanks!!

Reply

Roger

Hi Cindy,

Medium bed mortar has more sand in it, it prevents the mortar from shrinking as much as it cures. You should use it with all large format tile. You can just go over small cracks with redgard.

Reply

Cindy

Great. One more thing – do I need to backbutter? Don’t want to take the time and material if it is not necessary.
Thanks again for your help!!

Reply

Roger

Yes, always.

Reply

Theresa

I have plans to install limestone tile over a concrete base, outdoors, but covered. Rain water will leak through the porch over the intended area. Location: South Florida, so freeze-thaw is not an issue. What is the recommended product type for setting this stone?

Thanks!

Reply

Roger

Hi Theresa,

The manufacturer would be the one to recommend a product type if they wanted to. There are many approved methods for that type of installation, I would likely use hydroban over your base and set it with a really good modified mortar like mapei ultraflex 2 or laticrete 254.

Reply

joe

Hi- i used a poly blend mortar for my porcelian wood looking floors but ran out. I have left over mortar but this mortar is for mosiac tiles can i still use it to finish my project, less than 10 tiles left. Since it is mortar and not mastic is it ok? The bag just says its for mosiac tiles. I am neing cheap and lazy and do not want to go to store. :wink: also the area where i would use it is front entrane of laundry room so would get most foot traffic

Reply

Roger

Hi Joe,

I don’t know what polyblend mortar is. If it says mortar for mosaic tiles you should be fine using it on the remainder of your tile.

Reply

KIRILL

Hi,
I have to tile Tile Redi pan with 1×1 glass tiles.
There is an epoxy kit (three components) came together with the pan.
Im little bit worry that glass tiles will change color after installation since pan itself is grey. And as much as I know the epoxy is a transparent substance.
To camo grey color of pan the installation adhesive should be white for glass tiles, what material I should consider?

Reply

Roger

Hi Kirill,

You NEED to use epoxy to bond tile to the tile-redi pan. You can use white epoxy grout. The epoxy that comes with the pan cures a yellowish shade,

Reply

KIRILL

Thank you Roger,
Can you suggest which White Epoxy Grout will give a good result

Reply

Roger

Spectralock is very good.

Reply

KRisty

1952 house. Bathroom remodel. Just peeled up vinyl, glue, linoleum, and some kind of gray floor leveler (around the edges where they appear to have cut up the peeling linoleum?). I’m down to 1/2 inch plywood, sitting on floor joists. It has some kind of brown swirly non-water-soluble glue in the middle, and the remnants of black mastic around the edges. It’s almost even with my beautiful original hardwood flooring in the hallway, so I want to minimize how much I build it up.

What do I need to do to safely put hex tile on this stuff?

THANK YOU!!!!!!

Reply

Roger

Hi Kristy,

Get some Greenskin or Tavy thin-skin and install it right over your plywood, then tile directly to it.

Reply

COMike

Roger,

What are your thoughts/recommendations on tiling over an existing vinyl floor for a bathroom? I have read everything and still confused. Seems like the failsafe of course is to pull everything out (as painful as that is) down to the wood subfloor then throw down the backerboard.

I have read a number of people saying you can simply backerboard over the vinyl (screw the vinyl down first). Or another option sounds like to use an underlayment like Blanke Securmat Tile Underlayment…..where do I go?

Thanks for any insight,
Mike

Reply

Roger

Hi Mike,

If you use a membrane such as blanke or schluter you need to pull the vinyl up. While there are thinsets that claim they are acceptable over vinyl I ended up eating a job that had the toilet leak, my whole floor came up. So I don’t recommend that. The easiest would be to put down thinset then backer, and screw the backer down properly. The thinset isn’t there to bond to anything, it’s there to fill any voids. The screws in the backer will more than suffice to keep everything in place. You do not need to screw the vinyl down first, once finished it has nothing to do with your installation.

Reply

chris

I admittedly made the mistake as Bill and used premixed acrylic ceramic tile adhesive to tile the basement concrete shower floor with hex mosaic tile. A few days after that I noticed the shower faucet valve was slightly dripping before we had a chance to grout and the hex tiles literally peeled right off the floor as if they were just installed. I decided to take it all up and covered the concrete with Blue Seal waterproof membrane to seal the cracks and now am unsure as to what to use to reattempt tiling the shower floor PROPERLY. Help!

Reply

Roger

Hi Chris,

Regular powdered thinset is what you need.

Reply

ed

does it really matter which thinset type u use, ie porcelain or ceramic? I heard u cant interchange them, whats the diff ? I have 1/2 bag ceram left for use on porc floor tile. thx, ed

Reply

Roger

Hi Ed,

Not really, it just depends what you’re going over and what characteristics you may need in certain applications. With most installations you can use either. TCA specs require modified for porcelain, but it works just fine over ditra and it will work just fine over most anything else as well.

Reply

Delbert

Hi Roger
I would like to know if can use thinset on an elevated floor made with 3/4″ plycem cement board on 16 gauge steel C channels set at 16″ centers using ceramic tiles

Reply

Roger

Hi Delbert,

I don’t know. You need to get the deflection ratio of that floor. That will normally come from the joist manufacturer. You need higher than L360 for ceramic tile.

Reply

Dewey

this summer I want to install some tile, rated for exterior, on a porch slab. This is in Iowa with minus 20 degree temperature in winter. do I need to use epoxy or is thin set OK?

Reply

Roger

Hi Dewey,

Thinset is just fine.

Reply

Stuart

Hey, Roger! I’m over here now!

After reading your latest posts on modified and unmodified thinset and this page about proper setting materails, I still don’t know when to use which type of thinset. Specifically over a liquid waterproofer like Redgard. Can you point me to the deets please?

Reply

Roger

Hi Stuart over here!

About the only time to use unmodified is with schluter products. All liquid membranes require modified thinset, including redgard.

Reply

Stuart

Thanks again. I’ll go with your recommendations on modified thinset.

Reply

Stuart

Dammit! I thought I could figure this one out myself…I was thinking you had an article where you listed all of the common modified thinsets and rated them. Well I can’t find it. I did find the post about unmodified thinset in which you did just that but cant find the info for modified stuff. I’m going out today to get thinset to tape my seams and corners and to use to set my tile over redgard but I’ve read so damn many posts, replies, guides, etc here in the 24 hours that I’m losing my mind.

Thank god you are a patient man.

Reply

Jon

Hi

I have to replace a couple of broken pool tile can I use thin set to make the repair

Reply

Roger

Hi Jon,

Yes.

Reply

bill

Hi
I just finished a shower floor with premixed simple set mortor and just saw It should not be used on shower floors.do I need to tear it all up?Ive allways mixed mortor in the past and thought I would save some time would this last after grouting or not?

Reply

Roger

Hi Bill,

Yes, it needs to be removed. No, it will not last.

Yes, I know that isn’t what you wanted to read – sorry.

Reply

imran

Its cheeper now. Will cost way more later. I learned the hard way.

Reply

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