One of the most important aspects of a tile installation is the thin-set, and having even coverage under each tile. If there are voids, the tile may break, crack, or even pop up after a while. The best way to avoid this is to choose the correct trowel for the job, and applying the thin-set correctly.
To get complete coverage you will need the correct trowel for the job. Trowels range from completely flat (no notches) to 3/4″ x 5/8″ notch sizes. Mosaics and very small tiles up to 4″x4″ will require a small 3/16″ x 5/32″ to 1/4″ x 3/16″ v-notch trowel. Installing small format tiles from 4″x4″ up to 8″x8″ require a standard 1/4″ x 1/4″ notch trowel, but if you are doing anything over 8″ you will need to step it up to a 1/4″ x 3/8″ or possibly even a 1/2″ x 1/2″ notch trowel. 1/2″ x 1/2″ Trowels are the largest trowels we sell, and they are appropriate for large format tiles (any tile with a side greater than 15″), or tiles going over a very uneven sub-floor.
Do Not Swirl It
The norm with tile install used to be to make a swirling motion (see below) when applying the thin-set, but that leads to much less coverage under each tile. Applying thin-set in one direction, and applying firm pressure to the tile in a side to side motion helps close the ridges more effectively and give you 100% coverage under each tile. The video at the bottom of the page gives great visual examples and explains in detail why combing thin-set in one direction is best.