Recommended trowel notch size and other wall tiling tips? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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11-11-2011, 11:05 AM
Hello- this is my first post, but I've been lurking for awhile, and want to say thanks for all the helpful advice I've gleaned thus far. My hubbie and I are in the process of remodeling our guest bath, and we are (thankfully) at the stage to begin tiling this weekend! I wanted to get opinion/advice on the best size trowel (notch size) to use on each of our shower walls and bathroom floor before starting.

Our shower walls (currently hardibacker 500 with appropriate joints that I will be taping/thinsetting w/ alkali tape, will have 3x6 italian porcelain tile (staggered set), and the bathroom floor will be 8x16 italian porcelain tile. We will be using (currently) dry thinset (I think w/ latex additive already included- I'm at work and can't remember exact brand) that the tile shop sold to us- based on what I've read, I'm going to try to mix up relatively small batches (maybe a 1/2 gallon at a time) so that it doesn't dry out before I can use it, and will also lightly wet the cement board so that it doesn't pull the moisture out too quickly. I'm a little nervous about not using mastic, as it seems that diyers use that often b/c of better initial bond, but based on posts here it seems thinset is the better bet for shower areas.

Any thoughts on trowel size, as well as pro tips on keeping tiles from sliding/sagging while instaling would be much appreciated. Thanks, and Happy Veterans Day! :usflag:

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HooKooDoo Ku
11-11-2011, 12:03 PM
First of all, what have you done to waterproof the shower walls?

Hardiebacker is impervious to water (i.e. water will not harm hardiebacker), but it is NOT water proof (water can go through hardiebacker). Same thing for your tile and grout. The tile and grout protect the waterproof layer, they don't make the waterproof layer.

If you have already installed the hardiebacker and didn't install a waterproof layer behind it, you are going to need to apply a waterproof membrane over the hardiebacker before mounting tile (Redgard @ HD, Aquadefense @ Lowe's, Hydroban online or maybe a local tile store).

As for mastic, you don't want to use that in the shower either. It reemulsifies when it gets wet. So for inside the shower you definitely want thinset and not mastic.

As for mounting the tiles, well they ARE going to try to slide down the wall until the thinset ... sets. You will have to either attach ledger boards to support the 1st row of tile, or do something else to prevent the 1st row from sliding down the wall. Once the 1st row is set, you can use grout spacers to support the weight of the next row of tile on the 1st row of tile.

As for trowel size, read the instructions for your thinset. It should recommend a trowel size based on your tile size. If you have a mixture of tile sizes side-by-side, us the trowel size for the largest tile so that the thinset layer is the same thickness under all tile.

11-11-2011, 12:24 PM
HooKooDooKu, we installed 4mm plastic behind the hardi to provide a moisture barrier. I was planning to use a ledger to start the bottom row- even though some sites I've been on recommended starting in the upper center corner of the + I plan to map out on my wall to ensure proper centering of the tile, I thought that starting at the bottom row is the only thing that made sense.

I looked at the thinset bag, and it shows what my sq. footage would be using 1/4 versus 3/8, but doesn't tell me which one is recommended under which circumstances- then again, I was reading it this morning (without coffee) before coming into work, so maybe its in the small print and i just didn't see it...

11-11-2011, 02:39 PM
Jennifer, Here is a guide from CBP web site.

11-12-2011, 06:47 AM
Shapely- thanks for the follow up- I ended up finding the same guide online and used it on my 8 millionth trip to lowe's last night. Getting ready to start tiling (after I spend a couple hours prepping). Very excited!

11-12-2011, 07:08 AM
Jennifer, so many trips to Lowes. You should just get a room I know what you mean when I was doing my first project many moons ago I was going to the building place probably 5 times a day but it always gave me a break to get away from the work. Good luck on your project;)

Oh and on the trowel size, for that tile 3X6 porcelain 1/4" notch should be plenty. This is a trial and error if you haven't tiled before and I don't think you have. If you put the thinset on the wall and put your tile up and you got way to much thinset oozing out to clean up you got too much notch. More is not better. Using the right notch for any installation will save you having to clean up so much thinset in the joints. You want to have the joints clean as you go. Not clean them the day after when the thinset will be rock hard. I used a brush when I am installing tile, like a tooth brush but bigger and I clean out the joints as I go. They have them in the tile section of Lowes, yep one more trip.

The ledger board is the way to go and laying out the design, draw it out on your hardibacker. This way you know where everything is going to go before you actually do it. Not sure what you meant by what you said earlier starting in the upper center corner you want to start low and work high. If you do it this way you don't have to worry about the tile sagging because the ledger board will stop it from doing that. If you worked high and went low yes you would have to worry about sagging though they do make some awesome non-sag thinset but in your case there is no reason for you to do it. The tile shops do sometimes recommend the right thinset but often times they are just salespeople and like Joeseph mentioned no mastic(premixed) in the shower area it will break down eventually and it is messy!

Yes, you want modified thinset.

John Bridge
11-12-2011, 08:08 AM
Hi Jennifer, ;)

If when you start tiling the thinset starts poking out above the surface of the tile, you are putting too much on the wall. Conversely, if you lift a few tiles, and you don't have good coverage on the tile backs, you need a larger trowel.

The trowel size guides are okay, but they seldom take into consideration the flatness of the tile backs or the flatness of the substrate. Flat tiles will install well over a flat surface with smaller trowels no matter what size the tiles are. :)

11-13-2011, 03:11 PM
flat tile backs or not, back buttering tile is never a mistake