Crack suppression is used to minimize the tile’s exposure to stress from the slab.
Before setting the tile, you should walk the slab and look for cracks. If you only have a few cracks then you can use a crack suppression kit. If the slab is new or under three years old then crack suppression should be used on the entire area to be tiled.
Stones set on the floor require “mud-setting”. There are different methods to doing a “mud-set”. The most common is to use a ¾” square notch to trowel the floor, then trowel the back of the stone or butter the back with mortar.
Going over any other surface than virgin concrete you should use a multipurpose mortar (“pro” or “premium” flexible thinset). If you are setting a single fired tile or porcelain you should use a multipurpose as well.
Mastic is meant mainly for wall tile. The rule of thumb is to mortar the floors and mastic the wall. Mortar can be used to set wall tile; however, it is not very sticky and holding the tiles in place until they dry can be challenging unless you use a light weight flexible thinset.
n a word, no. Stones that are mud set can be butted. Tiles, because they are fired, will have some size variation depending upon the amount of moisture in the clay at the time of firing. 3/16” grout joint is the smallest we would recommend.
Porcelain goes through an added process, grinding the clay to make it very fine. When the clay is compressed, it becomes very dense and has very little moisture absorption making it ideal for outdoors.