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20x20 tile

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34K views 43 replies 18 participants last post by  MattCoops  
N
#1 ·
Hey guys/gals,
I am about to put 20x20 ceramic down and I wanted to make sure I am right or wrong on my trowel notch. I pretty sure I need to use a 5/16 deep trowel, am I right? Thanks.
 
J
#5 ·
Hi Norm and Rich,

There is no single correct answer to this. Lots of wrong ones though. With 20" tiles with a standard textured back I would recommend either a 1/4x1/2x1/4, or I might lean towards a 1/2x1/2 trowel, even larger might be needed?

Before you start the installation, can you tell me what the substrate is? If it's a wooden subfloor, have you consulted the framing and subfloor sheet requirements for tile? If it's a slab, are there any cracks or control joints or cuts? In either case that floor had better as flat as your kitchen table.

Specifically what thinset are you planning to use? Get back with answers to my questions above before you do anything.:thumbsup:

Jaz
 
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N
#7 ·
Thanks for the concern, my mother doesn't even care this much! It will be on a wood floor and I am using hardi backer as the cbu. It has 2x10 underneath at 16 o.c. I already went around and screwed the plywood(nalied previously) down for addition hold. The floor is quite flat and is only about 10 years old. I was going to use a modified thin set by laticrete. It is supposed to be for large format tiles.
where can I get the frmaing and subfloor sheets?
 
#6 ·
I have been taught it's more of the back of the tile that determines notch size. Besides, the bigger the notch size, the more mortar your putting down and there's a real good chance you're gonna have lots of mortar oozing from between the tiles. On ceramic that size, you'll probably need to experiment with back buttering too. I guess it really depends on how level the floor is. But remember the purpose of the mortar is to adhere the ceramic to what's under it, not to act as a floor leveling compound. You can make up some of the leveling with mortar but you shouldn't rely on it.
Start with your 3/8 x 1/4, mix a small batch and test a few pieces. Better to find out then that your trowel is the wrong size than to have a full bucket of mortar and realize it then!
 
B
#13 ·
I hate like hell to say anything around here anymore.:sad:

The :thumbsup: was two-fold because the information given was in my opinion good information and everyone seems to be under control......so......:thumbsup: (Not that my opinion matters.)

Nothing to add.:whistling

Well OK OK OK.

Keep a bucket of water and a sponge at your side at all times and if the thinset purges you can clean it up immediately.

Twenty inch tile can be a bummer if the subfloor isn't perfectly plane and they usually aren't. Spread the thinset and use the flat side of the trowel to "key" the thinset into the substrate and THEN comb the thinset in straight lines. THEN if needed you can skim some thinset onto the back of the tile using the flat side again. I have found "back-buttering" is usually required with tile that big.
 
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J
#14 ·
As I said there are many variables. You will probably have to try several trowels? Start with whatever you think and set about 2 tiles. Lift then right away to check for thinset transfer, you want at least 85% coverage. If you don't have it, go to the next one. Make sure the thinset is mixed fairly stiff, but workable.

If it was me and I was using a medium-bed mortar, (which one?) as it appears you are, I would not even consider the 1/4x3/8x1/4, that's my standard trowel for 12-13" tiles. I would start with the 1/4x1/2x1/4 but have a 1/2x1/2 standing by. They even make a 3/4" for certain situations. Remember when the tiles are beat-in, you should have a thinset thickness of a minimum 3/32-1/8", even a little thicker would be good with those huge things. Also remember, a trowel with 1/2" deep notches does NOT leave 1/2" tall ridges of thinset.

As for the subfloor system, we also need the unsupported span of the joists, species and grade if you can read that info off the joists and type of subfloor, thickness and number of sheets.

Jaz
 
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O
#16 · (Edited)
O
#18 · (Edited)
O
#20 · (Edited)
B
#22 ·
All of those books have something to offer. None of those books seem to follow an "industry line" too closely when it comes to approved methods. Haven't seen any of the recent Taunting publications, maybe they have improved although I doubt it. Some of the authors are quite informed and been around a long time but some of the information is shoot-from-the-hip at best in my recall.:whistling
 
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H
#26 ·
With 20x20 tile I wouldn't even consider anything smaller than a 1/2x1/2 square notch, and even with that I'd back butter.

Personally, I would use a 3/4" u-notch and skip the back buttering. But that's just me.

As for the oozing problem, I would rather contend with a little oozeage cleaning than have poor coverage under the tile.
 
F
#27 ·
Guys besides a tool to get the mortar on the substrate. A trowel is a measuring tool. The notches measure out the amount of mortar that gets on the substrate.

OK, if a 3/8 trowel gets coverage on a smaller tile. It is in theory, going to get the same coverage on a bigger tile. Why would it not, if the substrate was as flat as a pane of glass? How thick is the mortar bed under the tile. It is going to be the same, for all sizes of tile. This is just common sense. Now, go to a bigger notching. Are you going to get a better bond, if the smaller notch provided, equal and plenty of coverage before.

The kicker is, the flatness of the substrate and the profile of the back of the tiles. The bigger format of tiles makes the ability to level the tiles harder with less mortar, and you will not get near the coverage because of it.
 
B
#28 ·
Tom, What Bud's referring to is that fact that most books on tile setting aren't worth the ink used to print them. Unless they're written by someone Like Mike Byrne, or Tom Meehan, I wouldn't trust them.

As for the whole trowel size thing, with a tile that size or larger, the SMALLEST trowel I'd consider using is 1/2x1/2, and that's only with flat troweling the back of the tile, and ONLY if the subfloor is just about perfectly flat. Otherwise, it's 1/2x3/4, and it's medium bed mortar instead of thinset, and preferrably, they'd be mudset, instead. For large format, I'll choose mudset any day of the week, if I've got anything to say about it (I know-- that isn't very often). Otherwise you're pulling your hair out to get a perfectly flat floor.
 
H
#29 ·
Floordude said:
OK, if a 3/8 trowel gets coverage on a smaller tile. It is in theory, going to get the same coverage on a bigger tile. Why would it not, if the substrate was as flat as a pane of glass? How thick is the mortar bed under the tile. It is going to be the same, for all sizes of tile. This is just common sense. Now, go to a bigger notching. Are you going to get a better bond, if the smaller notch provided, equal and plenty of coverage before.
Click to expand...
While this would seem to make logical sense, in the real world, it does not.

Large format ceramic tile tend to be "domed" a little bit, even though they may not appear so to the naked eye. This makes it impossible to get good coverage in the center of the tile with a smaller notch, without adding extra mortar to the center of each tile. This will only slow you down.

You do make a good point about the extra mortar being needed to keep larger tile on plane, one that I failed to mention in my last post.

Hey there Bill, you look very familiar to me, hmmmmm, I just can't place where I've seen you before.:cheesygri
 
T
#31 · (Edited)
1/2x1/2in is the standard. Unless there are other things that need to be considered, like the floor being really bad, but the point is on a 20x20 I would never go below a 1/2x1/2 trowel, the tiles are just too big, and no floor is perfect. Most of the builders I sub for don't mind (so much) time or money, so for me I usually will just mudset tiles of that size and up. Also anything over a 16x16 is a new price range, it just takes ALOT more time to set them right, level and with no lippage.

P.S. I just read Bill's post after I posted, did not mean to repeat, I read the post and replied, and this is why I like reading Bill's posts our work seem to be similar, and not to mention most of the other guys on here try to say that the way I do things (mudset) is a dead art, takes too long BLAH, BLAH, BLAH. If you do not have enough time, and you really should mudset then you should fight for time, and money. It's worth it for me, less headaches honestly, and getting paid in the high $20/sqft always works for me also.
 
J
#32 ·
I have found that the flatness of the floor is so important with larger tiles.

A 1/2 x 1/2 trowel, once applied and the tile set will yield about an 1/8" of mortor - of course depending on the texture of the tile, etc.

Whatever trowel you are using, always lift a tile to check for coverage.

I believe that 90% transfer is what you are going for (minimum), unless doing exterior where you need 100%.

www.jarvisdesignbuild.ca
 
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