With the popularity of large-format tile continuing to grow comes the necessity of providing an adequate supply of thin-bed or medium-bed mortar to properly support and bond the tile. The question is, which trowel notch works best?

When searching for a trowel to spread this mortar, the availability can be overwhelming.  There are trowels with square notches, round notches, zipper notches and on and on. But again, which one works best and provides the best mortar coverage on the back of the tile?

When installing large-format tile, generally a larger notched trowel is used. This makes perfect sense. Right? Larger tile means more mortar, hence a larger notch. In most applications, this is true. But if we are using the time-proven Trowel and Error video method (moving the tile in a back-and-forth motion perpendicular to the straight line mortar troweling), we may have a problem. If a large format tile is being installed with a 1/8” grout joint, there is a limited amount of room to move the tile in the back-and-forth motion.

With a narrower notched trowel the amount of movement necessary is less, but with a wide notch such as a 1/2” x 1/2” x 1/2” trowel (which works well when properly used), the amount of movement required is significantly increased. The tile must now be moved at least 1/2” in order to fold the ridges of the troweled mortar into the valleys. This certainly is not difficult, but many installers say, “If I use a larger notch, I’ve got coverage.” Not necessarily so.

As you can see in the attached photo, the 1/2” notch was used; there was plenty of mortar to provide the required (80%) coverage, but what happened?  The tile was not moved far enough, so the back of the tile has huge straight line voids! This is a failure waiting to happen, possibly leading to hollow-sounding tile, loss of bond and cracked tile.

In the future when using a large notched trowel, be certain to move the tile back and forth at least the width of the notch and good coverage should be yours. However, get into the habit of occasionally lifting a tile to ensure you’ve got it. This quick and easy test will keep the money you make in your pocket, rather than paying for a repair or replacement.