Trowel Tips for Tile Insallation

April 21, 2017


Only one trowel type will deliver the correct coverage for a particular tile type. There can be only one.

Andy Acker, Director of Education for Schluter North America and Bryant Bouchard, Regional Manager for Schluter in the Northeast explain the nuances of the trowels used when setting tile.



Hi, Welcome to the Tips and Tricks video series. I'm Andy Acker, Director of Education for North America, and I'm Bryant Bouchard, Regional Manager for the Northeast.

BB: You know, Andy, I get a lot of questions over the years about what type of trowel to use when setting tile.


Thin-set does more than just glue tile to the floor

AA: Well, and the proper answer is the one that gets you the right coverage. We look at the industry standards, the coverage basically means the area that makes contact between the tile and the substrate. So, we're really counting on the thin-set to be there to not only bond the tile, but to support it also.

BB: Right. And when I think about coverage, I always tell my customers, if the coverage is really there, it acts like foundation or support for tile. So, the more coverage, the more support, the more long-lasting this tile installation will be.

AA: So, the industry standards also know that it's gotta be 85% coverage with ceramic tile, and 95% if it's a stone or a wet area. So, why don't we shoot for 100% coverage and see what we get from that.


Correct coverage comes from the correct notch size

BB: Yeah. And as you can see, we've got a lot of trowels in front of us and really, as a tile setter, you should have all these, because there's no real set standard as far as, "Oh, I'm gonna use this 1/4 x 1/2 with this tile." You really gotta take the trowel and install that first piece of tile, lift it back up and see if you are getting that 85% to 100% that you're talking about, Andy.

AA: That's right, Bryant. Well, we have a couple of trowels here that we offer at Schluter Systems. We have the DITRA Trowel and the Kerdi trowel, both very small notches, to put our product in, to put our membranes in. Okay, we have several different tiles here up on the table, different sizes, but also, different textures or finishes on the back. Right? 

BB: Yeah. And really, as you can see, there's different types of manufacturing processes. So, these are not flat, and this is why we recommend using the flat side of the trowel. So, we're gonna put thin-set on the back of these tiles and then use the flat side of the trowel to back-butter or flat trowel the back of the tile. Now, that's giving us two things. One, we're making the tile flat with the wet thin-set, and that's the same wet thin-set that we've combed on the floor, and that's where we're gonna set the tile down. So, this is gonna really help us get close to that 100% coverage that you're always asking for, Andy.


Back-buttering ensures excellent adhesion

AA: That's right. By the way, back-buttering is not an industry requirement, but it is strongly recommended when you get to a larger format tile, so that you make certain you get that bond. But I would go one step further than just saying large format tile. I'd say because of the texture on the back, the different configuration on the back, you're showing another tile that's completely smooth. It would still be a good practice on that tile there, which is a natural stone, to back-butter anyway.

BB: Right. Even though you can see this is pretty much flat, it's still a good idea to back-butter this, because there's porosity in the back of the stone. So, you're basically growing roots and legs of a thin-set. So, you're probably increasing bond by about 50% by back-buttering even on a flat stone like this.

AA: Right. It's always a good idea. We use the term burn in the thin-set in the back. We noticed when we were handling these earlier that we got some dust, maybe like some kiln release or some sort of dust off the back. So, back-buttering again, scraping with the flat side of the trowel is gonna make certain we really get a grab into that tile.

BB: Right. Because if we don't take care of this dust, basically, we're setting the dust to our combed thin-set.

AA: And it could be a potential bond breaker between the thin-set we combed just simply on the floor and the actual tile. So, various sizes up here. We've got the most popular sizes tile that are out here right now. Not only are they not flat, because of the configuration on the back, but they might not be flat as far as in plane either. So, that's another good reason. A lot of the plank size could have a concave to it, and so forth. So, that could come into play with hampering us with our coverage.


The right notch is found by testing

So, let's go ahead and talk about the techniques of putting the tile down, spreading and back-buttering, and then we'll actually put some in. We can put some right on this DITRA on the table here.

BB: Yeah. It's all about coverage, coverage, coverage.

AA: That's right. We just certainly wanna get the coverage, because that's the important part here, as you stated earlier. It's not only bonding the tile to the floor, but it's supporting the tile under load when people walk on it. It's a funny thing, floor tile is walked on. So, we're gonna need to get that done. So, as far as spreading, how would we go about just starting with a notch trowel? How do you select it? Is there a rule of thumb where we can generally get started based on the size of the tile? 

BB: Well, when you're looking at the tiles we have on here, Andy, I would generally start with this one, which is a 1/4 x 3/8 notch trowel. And...

AA: Good starting point. That's good.

BB: Yeah. Not to say that's the end all, but that's a good starter. We'll flat trowel first to the substrate, and then we'll comb, back-butter the back of the tile, put it in place, move it a couple of times, and then we'll lift it to check coverage. Now, if I've got 85% to 100% coverage, then I'm happy. I'll continue with the installation. If I have less than that, then I'll probably bump up to a bigger notch trowel.

AA: Okay. So, let's prepare a place here so we can set some tile. So, you grab what you're gonna need there, Bryant. I'll get the rest of the stuff out of the way. And I think out of all the tile we have, the most popular tile sizes on the market right now are the plank like this, but also, are the 12 x 24. So, why don't we go ahead and set a couple of those down here? So, you can see the back of these very similar to one of the 12 x 12 there. And we'll just set a couple right here and spot, so what are we gonna do here first Bryant? You want to show some improper technique? 

BB: Yeah, the first tile I'm gonna install, I'll use a 1/4 x 1/4 notch trowel. I won't back-butter, so basically, I'm gonna apply the thin-set to the membrane, and come back with the notch side of the trowel. I just wanna make sure I'm covering the whole area here. These are pretty big tiles, Andy.

AA: Yes, they are.

BB: Now, I'll do the notch and after this we'll set the second one, doing the method we described earlier.


Comb the thin-set in straight lines

AA: Okay. So, many times we don't see proper troweling where all the trowel marks in parallel like this. Typically we see, yeah, swirling pattern and that type of thing, and of course that's not the right way to trowel here with tile. But we'll put this tile in here.

BB: They're pretty heavy.

07:16 AA: That's it, it's a pretty good sized tile. And it is pretty heavy, and it might not be totally flat. Actually, the manufacturers are allowed a certain amount of tolerance here, as far as how flat this tile is. So typically they have a little bit of a concave to them. So they're just setting it in and then you didn't work it in. I see a lot of setters on the job site, all they do is just set it in and then they push a little bit. Maybe even a little bit like that. And that's about all they're doing. So now, proper technique, you switched over to... No, you haven't yet, you're still using that trowel to burn into the substrate.

BB: You're right, good catch, Andy.

AA: Well, we see that quite often.

BB: You'd make a good boss on a job.

AA: I could be a boss, couldn't I? [chuckle] All right, so we wanna...

BB: I will switch.

AA: You wanna key that in to make certain the cavities are all filled up. And now we're gonna go to...

BB: The 1/4 x 3/8.

AA: 1/4 x 3/8. Let's see what kind of coverage we get with that particular one. So now proper troweling technique is to put all the lines in the same direction. And the reason we do that is so we have the ridges standing proud right now, but then once we set the tile in place, after it's back-buttered, you'll see how Bryant works the tile into those ridges to have them collapse into each other. So that's what's gonna ensure our coverage, not only the back-buttering, but the actual proper vetting technique of the tile itself.

BB: I wanna mention this too, Andy. I'm holding the trowel at 45 degree angle, and that's ensuring that all the ridges stay at the same height as I move across.

AA: That's right. You don't wanna lay that trowel over too much because it becomes less and less of a tall notch when you do that. Like you said earlier, this is what the back of the trowel is for, right? You have a side that has the notches, which gauged how much thin-set we're gonna leave on the floor. And we have a flat side of a trowel. Our manufacturer did that so that you can actually do this process here. So, really, it just depends on the nature of the tile, but it isn't really important to build up a lot of thin-set on the back of the tile, but just burn some in. Now, since this is a rectangular sized tile and the manufacturer has allowed some tolerances out of flatness as far as the tile itself, they don't recommend that you do a 50% break on the joints here, for running bond, because that will have this tile's lowest point, next to this tile's highest point. So they're recommending probably about like a 30% coverage on there. So now you set this one in, and then I noticed that as you put that in, you did work that back and forth. You actually moved it back and forth and you could see since we're going across the ridges back and forth, that's gonna knock them down.

BB: Yeah. It basically rolls the notches right over, and every time we do that we find we're getting really close to the 100% that you want.

AA: Right. That's right, we're setting the tile. We're tile setters and that's important, that we're not just setting them in the thin-set, but we're actually working them into the bond coat. All right.

BB: Why don't we take a look at the cover.


Lift the tile to check the coverage

AA: Let's go see what we've got here. So first, the one with the swirls and the 1/4 x 1/4, no back-buttering, can we even get the thing up? All right. What have we got? Well, there's a machine that actually takes a picture of this and then reverse negatives black to white, white to black and it'll tell us exactly what coverage we have on there and I don't think, from looking at it, that we have 85% coverage on that, which would be the minimum for a ceramic tile in a dry area.

BB: So again, as we're talking about coverage and support for the tile, we're not even close, and if we're moving something heavy like a refrigerator or any type of car, this might crack.

AA: Yeah. And you can see the swirl patterns here. Where we weren't able to work the tile across the ridges and have them collapse into each other. Now let's take a look at the better coverage here.

BB: Let's hope it's better coverage, Andy.

AA: We're gonna hope it's better coverage, but this is good, this is the technique you should be using on a job site, 'cause once you put a couple of tile in, lift to make certain you're getting the coverage that you need. Oh, look it there, that looks like just about 99.8%. Wouldn't you say? I'm giving you just a little bit a leeway there.

BB: If we were on a job, Andy, you'd say that's the right trowel.

AA: That is the proper notch trowel. Another way that you can tell is when you set the tile and then you start working it in. If you hear that gritty grinding of the sand, you know you probably don't have the right trowel, you should probably go up a notch size there too. Well there you go so, improper coverage you can see you really didn't get the minimum coverage that we want here. Here we got, I would say, close to 100% on this particular tile. So, thanks for joining us here, we hope these tips help you out the next time you set tile, and you can achieve good coverage.

BB: And please visit our website, and check out our YouTube channel. Subscribe to it to see more videos just like this and these.


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