While any tile installation that must be waterproof does require grout to seal the joint between the tiles, many homeowners dislike the look of grout. If the tile job is to be done in a relatively dry area, such as wall tile or a floor that does not see a great deal of moisture, it is possible to install tiles without a grout joint.
To ensure that the tiles line up in straight, even lines and do not rub against one another causing damage in the event of the house settling, you must you vitrify tiles to complete the job.
Purchase tiles that have been vitrified. Vitrified tiles come in ceramic and porcelain for wall and floor use. The tiles are made of compressed clay dust and fired to extremely high temperatures. This ensures that the tiles are all completely straight and square, meaning that they can be installed butted up to one another with no grout joint. The tiles will stay in even rows and will not damage one another from movement.
Lay out the vitrified tiles over the area you wish to install them. Butt the tiles right up against one another so they are touching and mark any tiles that will need to be cut to fit with a pencil and straight edge. Cut these tiles on a tile saw before proceeding.
Spread a small amount of thinset at a time over the area to be tiled with a trowel. Rake the thinset with the notched end of the trowel and press each of the vitrified tiles into the thinset in the order determined by your layout.
Beat the tiles into the thinset mortar with a beating block. Hit them with the flat side of the block, not the edge as this could damage the tiles. The beating will ensure that each tile is completely flat and well-bonded to the thin set. This is important, because there will be no grout joint to make up for any lippage, or tiles that stick up slightly at the sides.
Allow the thin set to dry for 24 hours before you walk on the tile installation.
If you are laying tiles in a shower area, or area prone to a lot of moisture, you can still butt vitrified tiles together and then pack the joints with a small amount of unsanded grout. This will seal the tiles against moisture, while keeping the joint to the smallest amount possible.