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Selecting the correct tile adhesive is just as important as selecting the right tile for the project. The job of the adhesive is to bond the bottom of the tile to a surface, called the setting bed. In the last few years, there have been vast improvements in adhesives which make it easier for people to lay tile themselves, without contracting the job out to a professional. Organic mastics and thin-set mortar are most common, although latex, acrylic, and epoxy are also used.
The first step in choosing a tile adhesive is to consider the kind of installation involved in the project. A tile installer should consider whether the tile will be applied inside or outside, to the wall or the floor, or in a wet or dry area, among other issues. In addition, the installer should reflect on the kind of setting bed that will be used: drywall, concrete, plywood, or backerboard.
Organic mastics are among the most popular kinds of adhesives. They are commonly purchased because they do not require mixing and they help wall tiles stay in place without slipping. Those who use them must be careful of where the tiles will be set, however, because this type of adhesive shouldn't be used in locations that are exposed to heat or for tiles applied outside of the home.
The other most common type is thin-set mortar. It is usually mixed by the person installing the tile, and has a better bonding strength and offers more flexibility than organic mastics. This adhesive is applied to the tile in a thin layer, usually not more than 0.1875 inch (4.76 mm) thick. There are a wide variety of thin-set mortars available, so it is easy to find the right fit for almost any given job.
Water-mixed mortar or dry-set mortar is a form of thin-set mortar. It is a combination of Portland cement, sand, and an element that promotes water retention. This mortar is simply mixed with water and is beneficial because it allows the adhesive to hydrate. It is a favorite amongst the adhesives in the tile industry.
Latex mortar and acrylic-mixed mortar have additives that increase adhesion and lower water absorption, and either is perfect for wet or dry installations. Epoxy mortar is made from sand, cement, resins, and hardeners and is more expensive than most other tile adhesives. It is a good option when the setting bed is not compatible with cheaper adhesives. Medium-bed mortar is applied thicker than the rest — 0.25 inch (6.35 mm) — making it a strong option that is best for handcrafted tiles or those with uneven backs.
Following the general tile adhesive guidelines and asking plenty of questions at the home improvement store should make selecting the correct type easy. It is also important for consumers to read the instructions for each adhesive before purchasing one. Each company may have many kinds of adhesives, and some may have stronger bonding, quicker drying times, greater resistance to water, and less shrinking than others.