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The trick for getting better thinset coverage under your tiles

Improved thinset coverage
This simple technique can improve your thinset coverage on our tiles. © wabeno | Dreamstime.com – Floor tile installation

The trick for getting better thinset coverage under your tiles

I’ve worked with some fussy tile setters in the past. Everything has to be a particular way with them. The boxes of tile have to be opened a certain way, their spacers have to be positioned just so, and their tools have to be organized in a certain manner. Nowadays people call this OCD. Back then I didn’t know anything about OCD. I just thought they were being anal retentive.


What I didn’t realize is that these OCD tile setters had stumbled upon a technique to get better thinset coverage under their tiles. It’s something so simple but I always chalked it up to their “anal retention” and never saw the benefit of it. Until I watched a tile video demonstration that is.


poor thinset coverage
When the ridges swirl and go in different directions this can cause air to be trapped and lead to a lack of coverage. © Ginasanders | Dreamstime.com – Tile adhesive on a wall

The trick

It’s almost irresponsible to call this a “trick”. It takes no more effort than any other technique. And like I’ve mentioned already there’s some (the “anal retentive”) that are already doing this.


1/4 inch v notch trowel size
This technique isn’t just for tile. It should be used for installing membranes also.


Running your trowel lines all the same direction. That’s it. That’s the trick.


When troweling in circles or swirls air gets trapped in the ridges. Running them all the same direction gives air a way out when a tile is set upon them. Less air trapped in the thinset will mean improved thinset coverage. You may not think this is that big of a deal. But this troweling technique really does improve your thinset coverage.


The video below was made by Custom Building Products for the National Tile Contractors Association. It does a great job of showing how this technique works. It also talks a bit about trowel size and large format tile.


So that’s it. I never would have guessed the OCD guys were right. If you’re interested below is the original Trowel and Error Video. It’s worth watching just for the 1980’s wardrobe alone.




  1. Hey some good facts here. The proper way to trowel is perfect for me Did you use a 1/2″ trowel ?
    I’m about to start my first Porcelain tile job 6″ x 24 ” tiles, about 50 pcs, 5’x5′ and 30″ x 63″ l shaped bath room I used mortar under the Hardi board
    I have just finished screwing down my hardi board. laid a sample down and I get about 1/16 to 1/8″

    Will the thinset mortar fill this in? Or it may be better to stick to smaller squares
    today is Tue. I Plan on buying my tile Thur. and laying it Fri.

    Thanks Robert

    • I like a 1/2×1/2 growl for 6×24 planks but some guys prefer a 1/4×1/2.

      As far as floor flatness the tile have to be installed flat. The easiest and best way to make that happen is to use a floor flattening product like Planipatch which can be found at Lowes.

      Some people will build it up with Thinset but it’s not really the proper way.

  2. Great info! My kitchen is “separated” into 2 sections. Roughly 15’x15′ and15’x8′. There’s a crown in the floor at that “separation”. I put a 4′ level centered on the crown and its out about 1/4″ on both sides. After that the floor is flat and solid. I installed footings and a header in my crawl space (FUN) so deflection wouldn’t be an issue.
    Floor is as follows: 3/4″ plywood, 1/2″ grooved radiant heat plywood panels and will be installing 1/4″ hardiboard next in mortar. Tile will be 35″x6″ porcelain wood look planks.
    My hope is to install the Hardi board and gradually “remove” the crown in the floor. I know I can’t make it disappear. Am I crazy to try to trowel the mortar and even it out over the area of the floor. If I use floor leveler I will have a substantial step from my kitchen to the living room. Again the floor is flat, but of course it is pitched away from the crown towards the living room. I appreciate any suggestions u can give me.


    • I think I would forego the 1/4″ backer board. The you can self level each side up a bit and leave the center untouched. Then go over the whole thing with a membrane. For the membrane you could use Nobleseal CIS, ValueSeal both of which are under 1/16th of an inch. Or the slightly thicker Ditra or Redgard uncoupling mat (formerly called Spiderweb).

      That should keep your heights in check and still flatten the floor.

      • Cool. I’m concerned about the hot water radiant heat being trapped beneath Ditra or any other membrane you suggested, thus not heating the room. The manufacturer of the radiant specifies using the Hardi board. Thanks again

  3. Couple of questions regarding kitchen tile job we’re about to embark on. Thinking of using mastic instead of thin set? And what size trowel do you recommend when using 2×8 subway tile with a 1/16 gap? Just trying to not get too much mastic to push through when tile applied.

    Thanks :)!

    • 3×6 ceramic subway tile for a kitchen backsplash is one of the few mastic applications that I would say “ok” on. I would try a 1/4×1/4 square notch trowel for that and see how that works.

  4. Greetings, your information in very helpful. I am doing a about 9′ x 16′. I have removed much of the plywood flooring down to the I joist and will rebuild it. Although, I will do everything possible to make sure the floor is flat, I still anticipate possibly having to use some planipatch. My question is: Would I used this at the plywood level and then install hardiboard or install the hardiboard and then planipatch. Also complicating the issue a bit is the floor slants about 3/4″ in 4′ so I do not want the planipatch to level the floor.

    • You’ll want to use the Planipatch over the Hardibacker on the floor. The Hardibacker needs to be thinset down and either screwed or nailed. The tile doesn’t need your floor to be level but it does need flat. Sounds like you are on the right track.

      • Thanks! Your blog is extremely helpful!

      • Very good info Tile Guy. I love how you recommend specific products because they work not because you get sponsored by them. My question is do we really need to thinset hardibacker to the plywood subfloor if we plan to screw it in every few inches?

        • Yes, it’s important. The thinset acts as a bed for cement board. The screws hold it down and the thinset holds it up. You can get pockets and movement on the board with no thinset- even with using screws.

  5. 2nd question: I plan to use a Kerdi shower base and system. The floor is sloped about 1/4″ in 4 feet. Can i use planipatch to level that floor first and them set the base in unmodified? Thanks for the help.

  6. DIY Tile Guy, I am tiling a shower. Do i put the floor in first, and then the wall tile, or wall first, then floor, or, does it matter? Thanks!

  7. 3 inch hexagon mosaic wall tile, best to use 1/4 inch square or 3/16 v-notch trowel? Or either ok?

    • There’s other factors to it besides the size of the tile. I would start with the square notch. If you get too much thinset coming through the grout joints then try the v notch.

  8. One more question: My wall I am tiling on (cement sheet) is not totally flat/even. There are minor (4-5mm at worst) bumps and hollows. Should I bother trying to even this out using a thinset etc to fill/level the hollows or given the small tile size this won’t be a problem?

    • Your tile will follow whatever imperfections are in the wall. If there’s a dip in the wall there will be a dip in the tile. If you’re OK with the tile being imperfect then it probably isn’t a problem.

  9. I used versabond non modified thin set mortar to level the floor. the flooring substrate is concrete and cement backer board over plywood. I am installing lft (18×36) ceramic white base tile. tile was laid out on floor and all cuts were made. Tiles do not rock, so floor is flat. I plan to use versabond lft white mortar to cement to floor. will this have a satisfactory adhesion?

  10. I live in Tampa. FL

    I’m doing a floor renovation (2480 sq ft.) using ceramic wood grain tiles (5″x24″). The 1st floor substrate is concrete slab and second floor substrate is plywood…each substrate is approx. 1240 sq ft. I’ve decided to use the Schluter Ditra matting system and also Kerdi Shower systems for the 3 Bathroom remodels, 12″x24″ tiles.
    After extensive researching I have a few questions:

    (1) I have quotes from 2 suppliers here in the USA.

    One supplier’s quote is for 70 (50lb) bags of Ditra-Set Thin-Set and Medium-Bed Mortar and 10 (50lb) bags 253 Gold Multipurpose White Thin-Set Mortar.
    Subtotal 1,386.90
    Ship Price (Residential Delivery) 497.00
    Total $1,883.90

    Second quote is for 70/10 (50lb) bags, but the product difference is for
    Laticrete 317 unmodified thinset and Laticrete 253 gold.
    Subtotal 1183.20
    shipping 275.00
    total 1458.20

    Is it worth the price difference to go with the Ditra-Set?

    (2) Everyone says the ditra-set is the “best product”, is it because it’s easier to use, or is it really better stuff?

    • The reason for the difference is that all thinsets are not created equal. For plank tiles you’re supposed to use a LHT thinset (also called LFT, medium bed) which is for large tiles. Large tiles are defined as 15 inches or longer in one direction.

      Most unmodified mortars are not rated for large tiles. This would include Laticrete 317. However, that doesn’t mean that 317 is a bad mortar. In fact, I consider it to be a good unmodified mortar. But it’s not an LHT mortar (LHT stands for Large or Heavy Tiles).

      Ditra-set is a bit of a rare animal in that it has medium bed properties while still claiming to be unmodified. So if you are concerned about following Schluter’s rules and want to keep the warranty in place then you’ll have to use the Ditraset. If you aren’t concerned about their warranty then I still wouldn’t use the 317. Instead Laticrete has an LHT mortar, also 4xlt, Tri-lite, etc. These are all modified and are what Laticrete would recommend for large plank tiles.

  11. Very good info Tile Guy. I love how you recommend specific products because they work not because you get sponsored by them. My question is do we really need to thinset hardibacker to the plywood subfloor if we plan to screw it in every few inches?

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