In order to have a long lasting tile installation over your installed shower walls, you will need to have a very strong bonding agent, the tile adhesive, between the tile substrate and your tile pieces. The tile adhesive will do it’s part in securing your tile and protecting from normal house movements and shower usage. Your choice of tile adhesives will differ based upon the size of the installation, the area where it is applied, and the exposure to moisture.
Dry Mixed Adhesive
A dry mixed version of a thin-set mortar tile adhesive is popular due to the fact that you have a greater amount of control over the final product. The dry mix, consisting of a Portland cement base, only requires water, and experience will determine the exact consistency needed to be applied to the tile substrate and each tile piece. Each manufacturer has a proprietary blend of organic aggregates and chemicals that increase the bonding strength of their tile adhesive.
Another tile adhesive option is a pre-mixed version that is more commonly sold in a plastic container to increase it’s shelf life. The pre-mixed version can be easily identified, besides being in a plastic container, by the manufacturers use of the words “pre-mixed thin-set mortar” or “adhesive” in it’s name or description. While some manufacturers that use the words “pre-mixed thin-set mortar” in the description of their product may advise its use over a tile substrate, others that use the word “adhesive” will advise against against its use on a surface or in areas where moisture exposure will occur over pro-longed periods of time.
You should understand that some manufactures of pre-mixed adhesives use mastic as their primary bonding agent, these are most commonly that ones that use word “adhesive” in their description. Mastic is considered an organic adhesive and if submerged in water, it begins to deteriorate, therefore lessening the integrity of your tile installation. The manufacturer will advise whether their product can be used in a wet or only be used in a dry area.
Modified or Un-Modified
A modified thin-set mortar is considered to be a dry or pre-mixed tile adhesive which contains polymers formulated that increase its performance and strength. These polymers allow for the cement to retain strength, while also containing a sufficient amount of flexibility, therefore giving the tile installation over it a solid bond that allows for movement.
An un-modified thin-set mortar does not contain polymers. Where an un-modified thin-set mortar mix is used as a bonding agent, to increase its strength and flexibility, a liquid polymer can be added in place of water, or per manufacturer specification, during the mixing process.
Mixed or Pre-mixed
A standard tile installation over a tile substrate will use a mixed on-site version of a tile adhesive, The main advantage to mixing a thin-set mortar on-site is the control you have over the consistency of the final product. While a pre-mixed version of the tile adhesive is easier, your tile installation can benefit from the availability and stability of a mixed on-site version.
The application of your tile adhesive to the tile substrate of your installed shower walls and to each tile piece is just as important as your choice of mix and modification types. The tile adhesive should be applied with a trowel for better manipulation across the tile substrate. Where the tile substrate appears to not be level with it’s surrounding area, you can apply the necessary amount of thin-set needed to level the specific area of the tile substrate. Where you intend to install a tile piece, apply a sufficient amount over that immediate area, then using the trowels teeth, scrape to leave peaks and valleys. This will ensure that a vacuum seal is created when a tile piece is set over it. The tile adhesive is also applied to the back of the tile piece, referred to as buttering, covering the entire surface and removing excess at the edges. This will give you ample thin-set to ensure a solid bond is achieved with the tile substrate and also enough to allow for the tile to be manipulated and aligned correctly for a clean finished installation. It is also important to not use too much tile adhesive on the tile substrate and the tile itself, since excess would be manipulated outward, and if left to cure, there would not be available area for grout to enter in between each tile piece.