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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randy bullen

working with A GC. His tile guy has never heard of slaking. although he lays tile with perfect grout lines, the lipage it is so bad it’s referred to as toe stoppers. The lack of floor prep is driving me insane. lays directly on paint and drywall over spray on the floor. my question is is it allowable, proper,smart to mix regular thinset with fast setting thinset? I have worked with many tile people over the years and none have ever mixed the
two. seems like a terrible idea to me.



So, you can really use thinset to install waterline tiles in a pool? How about using it for a mosaic design on the wall of a pool where it will be completely submerged?
And, grout? What type should be used in both applications?

Thanks in advance for your time.



Hi Roger, I’m working on a shower following your site and it is going very well. Thanks for all the help. Question for in the rest of the bathroom where we want to tile half way up. It is a basement bath and will get wet from shaking dogs, but hopefully never really soaked. The only drain will be in the shower (on the other side of the curb). On the bathroom walls, should I install the tile on 1/2 backer board or just install it on moisture resistant drywall? I apologize if I an answer to this on your site.
Thanks again,



Hi Shane,

The drywall will be just fine in that application.



I have six 8″ square decorative tiles which complete a picture when placed in a 2×3 arrangement. In order to display them as a picture, I have had a custom frame made of aluminum (it looks like a cookie sheet). How / what do you recommend I use to adhere the tiles to the frame?



Hi Julie,

You can set them with epoxy.


Suzanne Bayder

I am working with a tile contractor. My tiles are 24″ marbilized porcelin for 1500 sq feet. He wants to use a thin set vs mud set. I am told only a mud set should be used with 24″ tiles. Which is correct. Are there cicumstances when you can use a thin set vs mud set on this job ? He is charging $6,000.00 to install a thin set. Is this a fair price to complete the job



Hi Suzanne,

A thinset is fine. What you are referring to as a ‘mud set’, I believe you mean a medium-bed mortar, which is also fine. A lot of factors come into play to determine what is appropriate. Fair price is relative. :D I will say that’s a hell of a lot cheaper than I would do it.



Hey Roger

Maybe you can advise me, I am laying Faux wood floor tiles over my existing tiles, I had two quotations today, second guy said I absolutely have to use formaflex, that’s what its called here in Spain, to glue the tiles down, problem is its 15€ per sq meter, works out the same price as the tile…!! can I not just run with the mortaro?

Please help




Hi Regina,

If you can scarify the existing tile so that it will soak in water when you splash some on there then regular mortar will bond just fine to it. But they need to be able to soak water in or it won’t bond correctly. If you use the formaflex you don’t need to do that.



Thanks Roger, I will be using ditra as a substrate so unmodified it is…


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