Hi, I’m Jeff Patterson, founder of Home Repair Tutor.
And I’m Sal DiBlasi, Elite-tile Company. I’m from the Boston area.
And I’m in Pittsburgh. So we figured even though I’m a Steelers fan—I’m sure you’re
a Patriots fan—we’ve come together to make this great video on thinset.
We’re going to divide the video up. I’m going to be talking about some areas that
I made, especially spot bonding. And Jeff is going to talk about the proper methods
of… How to apply the thinset to the back of the
tile, commonly known as backbuttering and the pattern of the thinset that you want to
see whenever you’re applying it to the wall or a tile.
One of the major problems when installing tile is the actual application of the thinset
and the troweling and just the coverage of the thinset. So we felt that it was important
to give some good information on what the proper methods are and what the problems are.
So these quick tips, hopefully they help you with your own project when it comes to tile
work, and they help you do the project the right way. So we’re going to be jumping
into the video. The first part of the video is going to be Sal sharing his knowledge about
what you should do, what you shouldn’t do with the thinset.
I’m going to go over one of the most common areas, and Jeff is going to give us some information
on the things you should actually do. So, we’re going to jump into the video right
now. Thanks.
Okay, so what we’re going to talk about today is spot bonding, which is an improper
way of installing tile on a surface, whether it be a wall or a floor. Now what is spot
bonding? Spot bonding is when you get a tile. You mound globs of thinset on the back of
the tile. Most of the time it’s like five globs, but sometimes there will be six or
nine. But it doesn’t really matter how many. The point is that they put globs or mounds
of thinset on the back of the tile. Then what they’ll do is they’ll get that tile and
push it into the surface, whether it be a wall or floor. And the reason they do this
is because it makes it easy for an installer to get a flat, even surface and get very little
lippage or eliminate lippage because they can push the tile in and out a corner or whatever
and get the tiles even. The problem with that is that thinset is not designed to be used
in globs. What happens is you got the tile on your wall,
let’s say, and you’ve got these mounds and you push them into the substrate, and
you got a nice, even surface. Now in the back of the tile, you’ve got all kinds of voids.
Very little of the tile is actually supported. So you’ve got a lot of empty spaces behind
the tile. And the other issue with that also is that
the thinset, as it dries, it’ll shrink, pull away from the tile, and leave the tile
with very little support and very little bond. Now some guys will also spread a layer of
thinset with their notch trowel on the surface and then they put the mounds on the back of
the tile, the spots, and then they push it in, thinking that that way they’re going
to get good coverage. Not true. Doesn’t happen. There’s still going to be a lot
of empty spaces. Another reason to do this is because you can
avoid doing the needed prep work. If you’ve got a rough surface and it’s not well prepared,
you can get a flat, even surface without doing hardly any prep because you got these big
globs of thinset behind the tile. So doing it this way by the time you’re done, and
you’ll probably going to have a nice, good-looking tile job, even, etcetera, etcetera. But in
short order, you’re going to get all kinds of problems.
Because the tile isn’t properly supported—I’m just going to go over these details on how
to spread your thinset, what kind of coverage you’re supposed to have, etcetera, etcetera—because
you don’t have the recommended coverage and you don’t have the support that the
tile needs, it’s subject to cracking very easily, to become completely unbonded to the
floor, the corners can crack, you can break off all the voids behind the tile; it’s
just a big, huge issue. So if you’re in a dry area, you’ve already
got huge problems. Now if you do that in a wet area, you’ve got even more problems.
Because, let’s say in a shower stall, you got all these voids behind the tile. You got
all these empty spaces. And the water in the shower is going to penetrate behind the tile.
And as it gets behind the tile, it’s going to accumulate, and you’re going to get mold
and mildew and who knows what else growing behind that. So that’s another problem.
And then the tile can also discolor, and depending on the kind of tile, you get dark and light
areas of tile, discoloration, all sorts of things. Have you ever even seen mold especially
on natural stone? Have you ever seen mold grow inside the tile? The actual tile has
mold growing in it. So if you’re going to install tile, you
need to use proper methods, proper procedures so that you don’t run into these issues.
Yeah, sometimes you can find a method that is going to make it a little bit easier, that’s
going to give you a good-looking job with less effort. But by not getting the coverage
that you need for the tile, for the thinset, in short order, you’re going to have all
sorts of problems. These are just some of the problems that you
can have. Jeff is going to go over the main points that you need how to use thinset and
what you need to achieve for proper calibration—that kind of stuff. So I’m going to hand it off
to Jeff, and he’s going to vie you some good information that you really need to know.
In this part of our video, we’re going to be talking about thinset coverage and backbuttering.
Is backbuttering absolutely necessary? It is absolutely not. But it does provide you
with extra insurance that your tile is going to stick to the substrate.
Many of the tips that you’re going to see here in a second come from the TCNA handbook.
If you’re not familiar with the Tile Council of North America handbook, check it out. It’s
a really great guide. So for example, in the TCNA handbook, they
recommend that 80% of the back of the tile be backbuttered if the tile is going to be
in a dry area. What do you do for a tile that’s going to be in a wet area like a shower or
a bathroom floor? Well the TCNA recommends that 95% of the back of the tile be covered
in thinset. We’re going to go over that in a moment here.
Also, you want the thinset to be evenly spread on the back of the tile. You don’t want
20% to be right here, and the other 60% to 70% of it to be all over here. Just evenly
spread the thinset on the back of the tile. The other super important thing when thinking
about thinset coverage is the size of your notch in your trowel. So here is a KERDI trowel.
It’s a 1/8” x 1/8” square notch trowel. You would never use this to adhere or set
tile to a wall or floor. It’s only good for KERDI-Board. This, on the other hand,
is a ¼” x 3/8” x ¼” square notch trowel. And this is a really great option for certain
tiles. And by the way, if you’re looking for a
recommendation on how to choose the correct trowel size, click right here. There’s a
video by Sal that’s phenomenal. You should definitely check it out.
All right, let’s do some testing. This is just a standard 12” x 12” tile,
and I’m going to turn it over. As you can see, the back of this tile is not flat. If
it were, you could technically use a smaller trowel and still get good coverage on the
back of the tile by backbuttering and by using directional troweling on the wall or the floor.
But as it stands, you can see this is not flat, and you have a lot of voids in here,
and there’s porosity to the tile. Because of all the voids on the back of this tile,
it is advantageous to backbutter it because you’re going to fill in all these voids
and the pores with the thinset. And this will make it easier to achieve recommended coverage
when the tile is placed on the comb thinset that’s on the substrate.
Okay, so let’s dive into our test. Test number one is going to be using this Schluter-KERDI
trowel. Totally undersized. Definitely not meant for adhering tile to a substrate. This
first test, we’re just going to spread the thinset onto the substrate here, which is
KERDI-Board reversed. So we’re just going to trowel the thinset on one direction. Here’s
our thinset. We have our directional troweling. So all the ridges are going in one direction.
We’re just going to put our tile on it and push down firmly into the KERDI-Board. So
I’m going to take this tile off and turn it over for you.
If this tile were white, it would be even more apparent. But the coverage here is terrible.
It’s not great. None of the thinset is in the voids of the tile, and that’s not good.
This tile would definitely come up off the substrate over time. So this goes to show
you that an undersized trowel is not good. This next test, we’re going to be using
a ¼” x 3/8” x ¼” square notch trowel. And what I’m going to do is show you why
directional troweling is super important. Directional troweling is basically north,
south, east, west—all the trowel ridges are in the same direction. Sometimes when
you see videos on YouTube, you’ll see somebody do these swirl patterns.
So no backbuttering of the tile here. We’re just going to set it firmly into the KERDI-Board
or whatever substrate you want to pretend this is. And we’re going to move it back
and forth, too. All right, let’s go ahead and pick up this tile. So look. This is why
directional troweling is good. This is a fairly big notch. You can the trowel ridges are not
collapsed. There are air pockets in there. And the back of the tile isn’t very well
covered at all. There’s lack of coverage here for the thinset. I don’t even know
what this approach is in terms of the coverage. Not good. Definitely not 90% to 95%. So that’s
why directional troweling is super important. For this next test, we do have directional
troweling. All the ridges are running in the same direction. And we’re going to backbutter
the back of the tile using the flat side of the trowel. So we’re going to fill in all
the voids. So we pretty much have almost 100% coverage on the back of this tile. So this
is backbuttered with the flat side of the trowel. Now we’re going to embed it into
the directional ridges here. And we’re going to move the tile back and forth. We’re going
to collapse the ridges. All right. Now let’s take a look at the back of this
tile. So as you can see here, we’ve got great coverage. All the ridges were collapsed.
The air is allowed to escape from those ridges. So when you collapse the ridges, the air is
expelled from them. And you collapse the tile onto the thinset, and you get great coverage.
As you can see, all the voids in the back of the tile are covered in thinset. And it’s
really the collapsing of the ridges that provides the coverage.
This final test, we have directional troweling. So all of the thinset is in one direction
on the substrate. And we’re also going to do directional troweling on the back of the
tile. So the direction of the notches on the back of the tile match the notched pattern
on the substrate. So what we’re going to do is adhere this tile to the substrate. I’m
going to clean this tile off in a second. But we’re going to collapse the ridges.
We’re going to move this tile back and forth just a little bit to collapse those ridges.
Expel all the air out of the thinset. All right, let’s take this tile off the
KERDI-Board. And again, you get great coverage when you use directional troweling, and you
use the double-notch technique. Well that’s it. Hopefully you like these
quick tips and they help you out with your own project. Make sure you subscribe to Sal’s
YouTube channel. It is phenomenal. If you’re doing tile work, you definitely want to watch
a lot of his videos. And don’t forget to subscribe to Jeff’s
channel because he has some really good information in his channel, and I think you’re going
to get some really good value out of what he does. And don’t forget Home Repair Tutor
as well. Well thanks so much for watching and make
sure you leave your comments down below. We’ll definitely try to answer them, and we hope
you have a great day. And remember, subscribe.