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 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 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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Can i use mastic 500 for shower glass tiles. 12×24.
5 1/6 thick.



Hi Sergio,

No. Call the manufacturer and they can give you setting materials you can use.


Ray M

I just bought all new tiles for my bathroom remodel. The brand is Brennaro Splendida tiles that were not cheap. When I picked up my order the sales lady told me the the wall tiles in the shower area must be applied using tile glue, not thinset mortar, according to the manufacturer. I’ve never heard of this and couldn’t find any info on this requirement anywhere else. I’ve always used thinset in the shower area and refuse to use anything else, but I don’t want to ruin all these expensive tiles. Any insight on this dilemma will be greatly appreciated.



Hi Ray,

I have NEVER heard of anything like that. Did the supplier also sell mastic? :D I would contact the manufacturer directly – that sounds like a line of BS to me.


Ray M

Yes that’s what I figured. She did try to sell me a tub of tile glue that I should use for an extra 40 bucks. I’m glad I didn’t take it though, thank you!



After laying the final top deckmud layer do I need to apply anything before I apply the thinset for the tiles?The reason I’m asking is the shower mud floor is really sand , does the thinset adhear to the sand.



Hi George,

It’s supposed to be sandy, it’s normal. The thinset locks in all that loose sand and it will bond extremely well.



Want to lay porcelain tile on sub floor without using back board. Cost of labor and back board is really high. Is there an adhesive that can be used? Floor has carpet and vinyl now, is over a basement. Doing close to 900 sq ft



Hi Nina,

You said basement, is your subfloor cement? If so, yes, you can remove the carpet and vinyl and bond it directly to the concrete. If your subfloor is wood, no, you need an underlayment.


Guy G

I am tiling my shower floor and bench with 18 X 18 tiles. What mortar do I use? And how should I do the front corner on my bench? top tile on top of the front tile?
Any help would be greatly appreciated.



Hi Guy,

There are a lot of proper choices for thinset for your tile. Mapei ultraflex, versabond, laticrete 253, etc. It mostly comes down to what is available near you. Yes, top tile over the face tile. I normally put a row of bullnose tile across the front of the bench so you have a finished transition there.



You are way too busy Floor Elf! Have a beer!!!! ?


Jim Willoughby

Question I putting a floor in my daughters shower actually a complete rebuild. I am down to the floor and someone sold her Redi poxy to glue the small tile in the shower. I have read comments about the Redi poxy setting very quickly. Since i work by my self and i am an old man and work slow. I am worried about the poxy setting up on me. I have no instructions on mixing small amounts. My question is what is best for this job?



Ok here’s my delima. I installed a nice porcelain tile shower tiles are 12×24.
I was going to use corner metal shelves, (soap/shampoo) that matched shower. Shower complete. Nice job if I say so my self. Since then the wife wanted granite counter top and on tub deck lid. Now here the delima she wants to use the same granite for the corner (soap/shampoo). Question is do I have to tear out tile and install granite. Or can I epoxy it to tile (cutting slots in it and wall for biscuit) and glue it to wall?


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