Thinset is an adhesive mortar made with cement and sand, that is often used to apply tile to floors, walls, and countertops. The name derives from its ability to bind objects with a relatively thin layer of compound, typically less than 1/4 inch (about 0.5 cm). It is available in powdered or premixed form and is usually applied with a notched trowel.
There are two basic methods for installing tile: mortar bed and thinset. The mortar bed involves laying down a thick layer of cement, usually about 1 inch (2.54 cm) thick. If there are irregularities in the flooring, the mortar bed can level them. This method is time consuming and the mortar must cure until it is "green," or nearly dry, before tile can be laid. It can take several days to complete.
Faster and easier to use, thinset can be applied directly to the subsurface. Installation is typically quick, and it cures within hours. Fast drying thinsets can be grouted in as little as two hours. Since it dries so quickly, it is difficult to adjust tile after it is laid. Generally, only experienced tilers who work quickly and efficiently use fast drying mortar.
Thinset is not a leveling compound. If flooring or other area needs corrections, this material is not thick enough to allow for adjustments. It is also a brittle compound that tends to crack if the area shifts. To counteract this disadvantage, many thinsets are treated to increase their flexibility. There is also an acrylic compound additive available to increase flexibility and moisture resistance.
For wall, fixture, and countertop installations, unsanded mortar is generally used. Sanded mortar, to which more sand has been added, is used for floor tile installation. Premixed mortars are more convenient since they are ready for immediate use, but they are more expensive than dry mortars. It can be difficult to prepare dry mortar to the appropriate consistency, so, usually, only experienced tilers mix and use powdered thinset. "Do-it-yourself" individuals who are doing small tile jobs often prefer premixed thinset, since it is easier to use.
Both dry and premixed mortars are readily available at hardware and home improvement stores. Thinset is also available online and through catalogs. Many home improvement stores offer demonstrations or workshops to show customers how to do remodeling projects. Tiling and using thinset is a popular topic.