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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Hi Roger,

I’m remodeling my bathroom and I’m trying to estimate the thickness of the new floor to understand how it will mate up against the wood floor in the bedroom. I’m going to use Schluter Ditra over my OSB subfloor. Do I need to account for the thickness of the thinset under the tile? With the tile properly set on the Ditra, how thick would the layer of thinset be under the tile?




Hi Will,

With ditra and 5/16″ tile your total installation height, with thinset, will be an average of 11/16″, just under 3/4″.


robert hogan

what is the best thin set yo use for settng tile over acrylic surface with moisture involved



I am applying ceramic /
glass mosaic tiles over thick paneling above firelpace and also over. Current formica backsplash. I was told by Lowes assoc. To use Type 1 tile adhesive by this Correct? Thank you



Hey Roger,

For those of us not super familiar with the consistency we need for thinset, do you have any tips for mixing up a smaller batch than the entire bag? For example, when I go to mud my joints (not changes of plane), I will certainly not need the whole bag, and don’t want to waste one if I’m not doing the tile yet. But, I don’t know how to be certain I’ve got enough water (or too much, since I need to wait for it to slake to know I’ve got it right, but by that time it’s too late to add more water or thinset mix). On past jobs, I’ve weighed the bag before and after, then done some rough calculation on how much I’ve used based on how much water is needed for the whole bag, but this doesn’t seem perfect (maybe it doesn’t need to be).

I believe I read somewhere that you just mud your joints at the same time as tiling, so maybe I should just start doing that. Any reason I wouldn’t?

Thanks again!




When using a liquid topical for the walls what do you do about the valve openings? I have quite a few (showerhead, body spays, hand held, valves, and diverteres). Would I be better going with kerdi so I can use the gaskets?




Hi Corey,

This. :D



Thank you for your website and excellent instructions. About a year ago, I used them to build and tile a new walk-in shower and heated bathroom floor. My wife is so impressed that she’s informed me I’m now qualified to install a tile backsplash in our kitchen (happy wife, happy life).

The backsplash tile consists of random pieces of glass and ceramic that vary from 1/4″ to 3/4″ wide and that are 3″ long. They are arranged onto 12″ x 12″ mesh mats. The kitchen is about 12 years old, and the backsplash area is currently painted drywall.

Based on your information regarding setting materials, I understand that although mastic could work in this application, thin set mortar is preferred. However, what, if anything, should I do to prepare the painted drywall before attaching the tile? It would be a pretty big job to cut out the drywall and replace it with cement board.

Thanks in advance,



Hi Rod,

You can go right over the drywall as it is. And with ANY glass tile you have to use thinset, you can not use mastic – it’ll never cure under the glass.


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