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.

Previous post:

Next post:


I an making a small fountain and need to adhere 2″x2″ porcelain tils to backer board, should I use thinset or I have also been told to use weldbond glue. The fountain is only about 36″ in diameter. I’m using a metal washtub for the fountain.
Any information you can give me will be much appreciated



We have a new shower floor of 2×2 tiles. Our contractor used a sponge too wet and now grout ilines are indented and sharp edges of the tiles are uncomfortable. Also concerned about water standing in grout lines after showering. The grout is Laticrete Permacolor Select Grout Base.
Can we add more grout to make a smooth surface?



I have to repair about 10 sq ft of ceramic tile on a bathroom floor. The wooden sub surface has been badly damaged by a leaking toilet, but only enough to make it quite uneven. It is still solid 1/4″ down or so.
I believe I need a deep bed adhesive and hopefully a pre-mixed variety. I see weber.set on the internet, but it’s in the UK and I haven’t found any local dealer.
Can you advise?


Larry McCoy

I am putting in a shower in the basement. I had help plumbing everything in from a local handyman. I wanted a low entrance into the shower which ended up with a threshold stone of marble 4 1/2″ wide and just 1 1/8″ thick and 59 1/4″ long. So here’s my dilemma I have already install the threshold stone with a 40 mil vinyl liner as the shower pan, but when I checked the drainage the concrete floor is practically level with the drain. If i try to put in any kind of mortar bed in to get the slope to 1/8″ my tile will only be setting on about 1/8″ to 1/4″ of mortar on top of a vinyl liner around the drain area which I am afraid will crack out. I can make the mortar 1″ thick around the back and side walls but along the threshold I can only get 7/8″ thick which might be ok. Would an epoxy mortar hold up to this application with the thin bed better?


Jessie Tan

My husband mess up a lot of stuff and I keep having to find solutions.

One of my problems now is : can thinset be used instead of grout since its solid when cured? Does it stain later, can it be washed?



No! Dont use thinset for grout… is too rough and would be very hard to get even and smooth and it certainly isnt pretty…..its dark gray or white only.


Denton Fender

Quote: “When mixed properly (read the directions, no, really, read the directions) it is stable, not compromised by water or moisture, and rock solid…..” Unquote. The local big boxes stock three different pre-mixed thinset and EVERY ONE states in the directions it is NOT to be used for shower floors. So what adhesive is one supposed to use for a tile shower floor?



Can you use epoxy grout on a gas fireplace wall?


larry walden

I have a 34×48 tile-redi shower floor pan, when I opened the box that has the epoxy for the floor pan mosaic tile I see some of the epoxy had leaked, I’m not sure if I have enough to do the tile. what other choices do I have without waiting for another order from tile-redi. there may be enough to do the base mosaic tiles but not to do the first 12″ porcelain row from pan to wall. can you help me, thanks


Peter Pham

Thank you so much for the info. So helpful.



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?


Leave a Comment

;) :wtf: :wink: :whistle: :twisted: :suspect: :shades: :roll: :rockon: :oops: :lol: :lol2: :lol1: :idea: :guedo: :evilb: :evil: :eek: :dance: :cry: :corn: :cool: :censored: :bonk: :arrow: :D :?: :-| :-o :-P :-D :-? :) :( :!: 8)