Michael has recently pointed out (a bit more eloquently than I would have) that I have indeed been a lazy bastard and have not yet written this post. Apparently people actually want to know how to do stuff I do – weird, right? So here you go – making your ceiling shiny.

The main problem people have with tiling a ceiling is getting the tile to stay where they put it. Believe me, I’ve had more than one tile fall on my noggin before I figured out what works. Since I’m relatively certain you aren’t very interested in what doesn’t work I’ll tell you what does, it saves headaches – literally.

You do not need a $75 bag of non-sag thinset to tile a ceiling. Non-sag thinset is basically just thinset that is sticky – it’s great stuff! It’s also expensive stuff. You can accomplish the same with the $15 bag of regular modified thinset.

Before you start hanging head-bashers (ceiling tile) you should, as always, have the substrate properly prepared. They do not always need to be waterproof. It’s a good idea and never hurts, but it isn’t always necessary. The photos of the shower I have here was in a small bathroom with limited ventilation so I waterproofed the ceiling as well.

Photo 1

You should always ensure that the ceiling substrate is screwed onto the joists securely. There is a whole different set of physics at work on a horizontal surface that don’t apply to your vertical wall tile. Basically the entire weight of the full tile is pulling constantly on every inch of your tile. So you want whatever it is attached to securely fastened.

Photo 2

Photo 3

The first thing we’re gonna do is burn your thinset into the ceiling substrate – in this case it’s Kerdi. ‘Burning’ thinset into something simply means using the flat side of your trowel and skim-coating the surface. I use the term a lot and that’s all it means. It fills all the areas of your substrate or tile (whatever you’re burning it into) and ensures that your thinset gets a good grab on whatever it is. Photo 1 shows about half of the ceiling with thinset burned into it.

Photo 4

Photo 2 shows the back of one of the tiles we’re installing on the ceiling. See all those white lines? Those are actually raised just the tiniest bit so the back of the tile is not entirely smooth. You need to burn thinset onto the back of the tile. This will fill all those little squares and ensure that you have every area on the back of your tile adhering to thinset. You want to give it every square inch possible to grab onto that ceiling. Photos 3 and 4 show the tile with thinset burned into the back.

Photo 5

Now you want to flip your trowel over and comb thinset onto the back of the tile. “Combing” thinset is another term I use often – it just means using the notched side of your trowel to, well, comb the little lines all in the same direction. That is – wait for it – Photo 5. You are not allowed to give me crap about my lack of photo labeling originality!

Photo 6

Now we get to the secret ingredient of ceiling tile installation – suction! All that thinset you combed into pretty little lines on the back of your tile? Take the end of your trowel and draw a bulls-eye in it like Photo 6 (believe it or not I was totally sober when I drew that ‘circle’). This bulls-eye is what keeps the tile from dropping on your head – because that hurts like hell. You should just take my word for it on that one without testing it for yourself.

Photo 7

Now that you have your bulls-eye on the back of your tile go ahead and press it up onto your ceiling. (Photo 7) You want to push hard! You will actually hear air squishing out from inside that circle of thinset. This creates suction on the back of your tile and helps the tile stay put until the thinset cures. Once that happens it doesn’t matter what shape your thinset is on the back. The suction is needed to keep it there only until the thinset is cured.

Photo 8

Continue to do this with the rest of your ceiling tile – every one of them, even the cut tiles. Draw the bulls-eye and stick it up, draw the bulls-eye and stick it up, etc., etc. To get them to stay in the proper spot with correct grout line size and lined up you can actually stick spacers in them (Photo 8 ) and use blue painter’s tape to keep them in the proper spot relative to one another. Just get a piece of tape about 3 -4 inches long and stick half of it to one tile then pull that tile slightly toward the one next to it and stick the tape to the next one. This will keep each tile tightly against the spacer and the tile next to it so your grout lines don’t go all wonky. (Did I just type ‘wonky’??? Jesus…)

You do not need to comb thinset onto the ceiling. I know that sounds counter-intuitive but simply burning the thinset into the substrate will give you plenty of grab onto the tile. You do not need to be concerned with 100% support as you would on a floor – no one will walk on your ceiling except Spiderman – he’s an ass sometimes. But he always pays to replace any ceiling tile he cracks.

Once you get all your tile up there you can still push them upward to get them flat with each other. Just lay your straight-edge across them as you would on a floor and make any adjustments needed. You do not want to pull them down to adjust them! You will lose the suction doing this. You want them really close to flat before you make any final adjustments.

Photo 9

You can see in Photo 9 (if you click on it) that there are two tiles that have slightly low corners which I still need to push up (they’re in the back row – the left corner of tile two and the entire front edge of tile four). Always push up to make adjustments. If your tile is way out of whack pull it down as you are setting them to add or take away thinset on the back. Do not pull them down once you have them all set and taped.

That’s it. That’s how you get tile to stick on the ceiling with regular thinset. Easy. Okay, it’s easy for me. You may have a bit of a learning curve.

There are two basic designs for your ceiling tile. You can either line up all the grout lines (which requires planning!) or you can install the ceiling tile on-point (diagonally). This is simply a personal preference – whichever you think would look better in your shower is the one you should choose. The photos here have all the grout lines lined up. If you do not install your ceiling tile diagonally please line up your grout lines. If you don’t it looks like crap – that simple.

When installing tile on the ceiling you want to install the tile on the shower walls all the way up to the last row before the ceiling – as I’ve done in these photos. If you are lining up your grout lines rather than installing them diagonally you can then draw lines on your ceiling as guides to where your tiles should be. You don’t see lines in these photos because I use a laser – I’m Star Wars-ey like that.

Once you get all your ceiling tile up then install your last row of wall tile. This will help hold all the tile around the edges as well. Be sure not to cut the last row of wall tile so that it barely fits in there! You need an expansion joint of about 1/16″ and you do not want the pressure of a wall tile that is not short enough pushing one side of the ceiling tile up – the other side will push down – leverage, you know. Cut them about 1/16″ shorter (plus your regular grout line size for the line below it)  than your measurement and use plastic wedges for that gap. And when you are finished – caulk or silicone that space, don’t grout it (unless you’re using epoxy grout).

The thinset I’m using is a basic modified thinset – nothing special. It’s Versabond which is commonly sold at Home Depot. You should know this, just to avoid confusion about an issue that is confusing enough anyway. Schluter recommends UNmodified thinset for the Kerdi membrane. If you choose to use modified thinset over the kerdi membrane it will void your warranty! Just be aware of that.

I use modified for two reasons: 1) I prefer modified thinset for everything – period. I give my own warranty to my customers which happens to be longer than Schluter’s warranty anyway. I take that risk and choose to do so – consciously. Should you choose to use modified thinset over kerdi you should be aware of this. And no – it does not create any problems that I have ever been aware of. Doesn’t mean it won’t, just means I have never heard of it. And 2) I’m a rebel like that.

If you have any questions at all please feel free to leave a comment and ask there – I’ll respond when I sober up! The gist of this post was shrunk down into a handy little four paragraph email for TileTips. You can click that link for more information or simply sign up in the box at the top right (under the pretty picture).

This post was brought to life by the suggestion of one of my readers in a comment. I really do read them! So I would like to thank Michael for kicking me in the ass and making me do something productive! My wife thanks you, too. If there is a particular subject you would like to see a post about just let me know – I’m a wealth of useless information.

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.