Using the proper trowel

by Roger

One of the most frequent questions I get asked is ‘What size and type of trowel should I use for…?’  The proper answer to that is ‘whichever trowel gives you the proper coverage for your particular installation’.

So there really isn’t one perfect answer to that question, a lot of factors are involved. But I’ll try to help you out.

Proper thinset coverage

The first thing you need to know is what constitutes proper coverage.  As stated in ANSI A108.5 3.3.2 for installation of tile on floors; “Average uniform contact area shall not be less than 80% except on exterior or shower installations where contact area shall be 95% when no less than three tiles or tile assemblies are removed for inspection. The 80% or 95% coverage shall be sufficiently distributed to give full support to the tile with particular attention to this support under all corners of the tile.”

Let me translate that for you:

Proper coverage of any tile in a dry area (bathroom floors, backsplashes, fireplaces, etc.) is 80%. Proper coverage of any tile in a wet area (showers) or outdoors is 95%. This includes complete coverage beneath all corners of the tile. You check this by installing a tile, then removing it to check the CONTACT of the thinset on the back of the tile. If, after checking three different tiles in three different areas of the installation, you have that percentage of coverage then you have proper coverage.

Example of Full Coverage

Correct complete thinset coverage

Always aim for 100% coverage. More is always better. The photo to the right is an example of complete coverage (thanks Rob).

If you have less than that percentage of coverage you have a couple of options. You can either back-trowel the tile as well as the substrate (back-troweling means combing lines of thinset on the back of the tile as well, not just skimming it with the flat side of the trowel which is called backbuttering), or you can switch to a larger trowel. Both methods will give you more coverage. In the case of back-troweling it will double the amount of thinset beneath your tile.

So those are your coverage requirements and how to check it. Now onto different trowel types…

Types of trowels

types of trowelsTrowels come in a lot of shapes and sizes, even goofy lookin’ ones that look like something out of a Saw movie. The three basic types you should know are the square notch, U-notch and V-notch.

If you look at the horrible graphic I made (my photoshop skills are like a monkey with ten thumbs opening a banana with the keyboard…) you’ll notice that a V-notch will leave the least amount of thinset on your substrate, the U-notch more than that and the square notch will leave the most.

You would be able to visualize this if those horrible graphics were to scale and all the same size. Which they aren’t. Whole monkey-thumbs keyboard-banana thing…

With any mosaic tile you normally want a v-notch, with any large format you normally want a square notch. With average sized tile (12 inches square up to 17” square) you’ll want a u-notch or square notch. With most of my installations I use a square-notch trowel.

Sizing trowels

1/4" X 5/16" V-notch trowelTrowel measurements can be confusing – some have two numbers, some three. So you need to know how to read them.

V-notch trowels normally only have two numbers. The first number is the width of space between the teeth, the second is the depth of the notch.

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1/4 X 1/2 X 3/8 TrowelWith square notch and U-notch trowels  the first number is the width of the teeth, the second is the width of space between those teeth, and the third number is the depth of the space between the teeth. Like this:

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1/4" X 3/8" square notch trowel

If it only has two numbers it means the width of the teeth and the width between the teeth are the same and the second number is the depth of the notch, like the one on the left.

This is the most common sizing you’ll find on a trowel.

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1/4" X 1/4" square notch trowel

If it only has one number, or a trowel is only referred to with one number (as I often do when recommending a trowel) it means that all the measurements are the same. This is what I commonly refer to as a ¼” square notch trowel, even though the graphic says U-notch.

Monkey, thumbs, banana. Yeah.

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SQUARE NOTCH!Here:

Better?

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Which trowel to use

As I stated at the beginning there is no one answer to that. All I can do is tell you what I normally use with what size or type of tile.

1/4" X 1/4" V-notch trowelIf I am installing smaller mosaics (smaller than 2” square) I normally use a ¼” V-notch trowel. This is a ¼” X ¼” trowel.

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1/4" X 1/4" square notch trowelWith mosaics or regular tile larger than 2” square I will use a ¼” square notch trowel ( ¼” X ¼” X ¼”).

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1/4" X 3/8" square notch trowelWith tile 12” x 12” up to 18” x 18” I’ll normally use a ¼” x 3/8” trowel ( ¼” X ¼” X 3/8”)

With tile larger than 18” I’ll either use the ¼” x 3/8” and back-trowel the tile as well, or use a 3/8” X 3/8” or ½” X ½” square or U-notch.

Those are general guidelines and will work with most installations. You NEED to check your coverage with your installation to ensure that you have proper coverage. If you do not have proper coverage you need to back-trowel the tile or use a larger trowel.

The trowel I normally have in my hand is a ¼” X ¼” X 3/8” square notch, I use it for most of my installations (and to irritate random pets…).

This is another one of those questions that, if you ask 50 different contractors, you’re likely to get 50 different answers. For instance the photo of the tile with full coverage at the top is from Rob. It is a 13″ X 13″ tile and he used a 1/2″ x 1/2″ trowel. For most guys it is a personal choice. As long as you get proper coverage there is no wrong answer. The above are simply guidelines and my personal choices. It is up to you to determine whether your trowel is the proper choice for your installation or not.

I can’t see your installation from here. And you know what happens to your dog if you get improper coverage, right?

If you don’t you need to read my blog more.

Just sayin’.

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Tracey

I bought 4×8 glass tiles with metallic blue back paint. The back color must be on very well; had to remove them and start again twice. Finally found out the mastic was the wrong thing to use. Still looking for correct way to attach to shower wall (it is on Durarock). The stuff I bought the second time says not for tiles larger than 6×6 & not for use on glass tile with decorative backs due to chemicals in the thin set. Next the floor will be 12×24 ceramic tile again onto Durarock. The floor has a slight slant in one corner…thought self leveling stuff would work…then what? Am I on the right track? Would like this to be the last time to do this and have it last. :evilb:

Reply

Roger

Hi Tracey,

You need regular powdered thinset that is sold in 50lb. bags that you mix with water. There is no premixed product that will work with glass, or in a shower. Yes, the slc will level up that corner, then the same thinset is used to install your floor tile.

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Kevin

Hello, I am installing 12″x 12″ mosaic tile on a mesh backer. The instructional video calls for using a 1/8″ v notch trowel but all I can find is either a 1/8″ u notch or a 3/16″ v notch trowel. These are going up on a wall. which would be best to use? Thank you.

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Roger

Hi Kevin,

3/16″ would be better.

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Kevin

Roger,

Great site. I’m installing a mother of pearl 3mm mosaic backsplash. My plan was to use the smallest trowel I could get (1/8″ V) since the tile is so thin. I can’t seem to find anything online pertaining to such a thin tile. What are your thoughts?

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Roger

Hi Kevin,

Take the v-notch, comb the thinset onto your wall, then flip the trowel over and knock down the ridges so you have a flat, even bed of thinset. Place your tile up there and you can embed them into the flat bed well with minimum squeeze-through. Keep a toothbrush handy in a bucket of water and run it through the grout lines as you install it to remove any rogue thinset.

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Gerald

Hi,
I am currently doing some research to make sure the end result of my project is 110% and was looking for your advice if you have come across this. I am doing 1/8 inch thick by 1 inch octagon mosaics on a floor in a heritage house and was wondering the best suitable sub-floor as well as best adhesive and trowel size for this application. Also would it be best to flat trowel to avoid adhesive from coming through grout lines? Thanks!

Reply

Roger

Hi Gerald,

The best substrate for that would be either slc or cement backerboard. You want to trowel the thinset on with the ridges, then knock the ridges flat. This will give you the thickness you need without too much oozing through the grout lines. You should use a 1/4″ v-notch trowel.

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Tim

Just started another tiling project. This is three bedrooms, just about 600 sqft. Thinking that the trowl was not working for me, I found this sight which suggested a trowel much larger then I would have ever used. I was able to work much faster with no lipage and using less thinset. I’m forever indebted. Thanks Roger.

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Patrick

Hi, I am installing 4×4 tile in a shower. Never did tile before and someone told me not to get to big of a trowel so the thin set dosnt come up through where the grout go’s. I am using a 5/32 v noch, wanted to check and see if it will be enough thin set on the wall to hold up my tile or should I get a bigger trowel? Thanks

Reply

Roger

Hi Patrick,
It will hold up your tile just fine provided you have 95% coverage of thinset on the back of your tile. Place your tile up there (install it), then pop a couple off to ensure proper coverage.

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teresa

Installing a 7×20 wood look ceramic tile on floor. Is there a recommended trowel size and notch?

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Roger

Hi Teresa,

Yes, whichever one gives you the proper coverage. :D Try a 5/16″, and move up from there if needed. It all depends on your tile.

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Lori

Hi Roger. This is a great site and excellent service for diyers. I have a question regarding the application of a product (which I don’t know of yet) that I’ve been told I need to apply to the back of my stone tiles (sandstone 16×24″) so that the mortar does not show through even thought I’m using white Kerabond (over Ditra and heat mat). The tiles are a very light sand color, hence the sandstone name no doubt! Duh. Have you heard of this? More info- my tiles are 3/4″ non-polished and you can see slight saw marks on either face of them as if there is no finishing on them. What Up?

Reply

Roger

Hi Lori,

I don’t know what product that is, but I do know it isn’t necessary if you use white thinset. It sounds as if your sandstone wasn’t honed well, which is the process that grinds down the face to make it smooth.

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Leo Christl

I am laying down porcelain tile 13×13, 6.5×6.5 and 13×20. There also is a border of 2 Inch x 2 inch tile. What size trowel do you use on the small square border tile and how do you get the right amount of thin-set under the border tile so they are even with the larger tile as I intend to be using a 1/2 inch x 1/2 inch sq. notch trowel on the larger tile? Please help? Leo

Reply

Roger

Hi Leo,

A 1/2″ is a very large trowel, you’ll likely be fine with a 3/8″ or 5/16″. As for the uneven tiles: Making mosaics flush

Reply

Chris

Thank you!!!!

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Chris

I’m installing 1″ hexagon tiles using a modified thin set mortar on a hardie board substrate. I see you recommend the 1/4″ x 1/4″ V-notch trowel. I’m having a hard time finding a V-notch trowel in that dimension. I can find 1/4″ x 3/16″ v-notch but assume that would not be sufficient? I have also found a 1/4 x 1/4 x 1/4 flat top v-notch trowel but also assume that would not be ideal either for proper coverage? Suggestions?

Thanks!!!

Reply

Roger

Hi Chris,

The 1/4 x 3/16 should work fine for your installation.

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Rich

6×12″ question was for floor tiles…should have stated.

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Rich

What about a weird size like 6″x12″? Notch U 1/2″ work best? Thanks

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Roger

Hi Rich,

Normally a 5/16″ or 3/8″ is sufficient.

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Adrian

Good morning Roger.

I searched the FAQ’s for an answer to the following question;

Can thinset be used to smooth out imperfections in a dry mix shower pan? If not, please recommend any products that would be suitable.

This being my first attempt at a custom tile shower enclosure, I would rather err on the side of caution.

Thank you in advance.

Reply

Roger

Hi Adrian,

Yes, it can.

Reply

MJ

Roger,
Happy New Year! I’m installing a backsplash with 1/2″ thick 2×4 marble tiles in roughly 12×12 sheets with netted backing. What trowel would you recommend (without being able to see my tile :-) ?

Also, do you think TEC Power Grout is OK?

Thanks,
MJ

Reply

MJ

You had mentioned a 3/16″ U-notch, but I can’t find that anywhere! Since my grout lines are variable from 1/16 to 1/8, I’d like to get the best coverage with as little thinset getting into the grout lines as possible. If you had to buy a trowel for this job, what would you buy? Thanks for your opinion on the matter.

Reply

Roger

I mentioned a 5/16″ u-notch. :D I would still use that, or any size you can find that is larger than that.

Reply

Roger

Hi MJ,

5/16″ u-notch. Yes, power grout is awesome.

Reply

MJ

Roger,
Have you ever heard of a “Euro-notch” trowel? Here is a link: http://www.contractorsdirect.com/Tile-Tools/Trowels/013-287-2-K-Schneegans-Holo-Top-Trowel.

Also, have you ever used a slanted-notch trowel?

In my quest for a 5/16 U-notch, which I can’t find anywhere (1/4 x 3/8 x 1/4 is the closest I can find), I stumbled on these and wondered if you had an opinion.

Reply

Roger

Yes I have used them – I like them. They work very well.

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bob

4 X 16 subway tile. trowel size for thin set

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Roger

5/16″ x 1/4″. Or, whatever gives you the proper coverage for your particular tile.

An extremely flat tile can be set with a 1/4″ trowel, an extremely warped tile may need a 3/8″ or larger. I can’t see your tile from here, that’s why I wrote this article. :D

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Mike

I am installing 1/4″ ceramic tile that will butt up against an existing wood floor that is 1″ higher than the plywood subfloor. My goal is to make the new tile level with the wood floor. I will be removing the existing plywood substrate on top of the subfloor under the old tile. Would you suggest using a 1/4″ notch trowel for the thinset under a 1/2″ hardiebacker and a 1/4″ notch trowel for thinset under the 16×16 ceramic tile? Or, would you suggest a 1/2″ notch trowel for thinset under a 1/4″ hardiebacker and same under 16×16 tile? The 16×16 tile is 1/4″ thick. Thanks a bunch!

Reply

Roger

Hi Mike,

1/4″ under 1/2″ hardi for the backer, then whatever size trowel you need to get the tile flush, as long as you get proper coverage for your tile.

Reply

saundra

HI, I am tiling a bathroom floor with 12x24in ceramic tiles. My floor in about 1/2 in unlevel from wall to wall. I already put down 1/4 in ply substaight. I bought levelquick to level but a large space of 14×8 to level. I was thinking if I put down 1/2in hardibacker then levelquick to feather out from there. I also bought spiderweb uncoupling mat to go over the rest? what do you think? I took out old doors so I have room for all that height.

Reply

Roger

Hi Saundra,

You can put down the 1/2″ hardi in the lower areas before the slc, but you want to put thinset beneath the backer first to ensure it doesn’t have movement under the slc, it could lead to cracking.

Reply

Tom

Hi,
My old house has very uneven studs. Can I use regular drywall shims under the hardiboard which will be waterproofed with hydroban? If not, what should I use to get things on the same plane?
Thanks,
Tom

Reply

Roger

Hi Tom,

Yes, regular drywall shims work great. That’s what I use.

Reply

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