STONE –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– and material specifications are con- tained in ANSI A108.5 and A118.1. 3.1.3 Latex-Portland Cement Mortar [Thin Bed(ANSI A118.4)] 3.1.3.1 Latex-Portland cement mortar is a mixture of portland cement, sand, and special latex additives which is used as a bond coat for setting stone tile. 3.1.3.2 Installation Methods. The uses of latex-portland cement mortar are similar to those of thin-set mortar. It is less rigid than portland cement mortar. 3.1.3.3 When latex-portland cement mortar is used to install stone in a wet area that may not thoroughly dry out in use (e.g., swimming pools and gang showers, etc.), it is recommended that the complete installation be allowed to dry out thoroughly (cure) before exposure to water. Consult the thin- set manufacturer for curing instruc- tions. Latexes vary considerably, and the directions of the latex Manufacturer must be followed explicitly. 3.1.3.4 Suitable backings (See 3.1.2.4 above). 3.1.3.5 Installation and Material Specifications. Complete installation specifications and material specifica- tions are contained in ANSI A108.5 and ANSI A118.4. 3.1.4 Epoxy Mortar (ANSI A118.3) 3.1.4.1 This is a thin bed mortar sys- tem employing epoxy resin and epoxy hardener portions. A two-part, 100% solid epoxy is to be used as the setting bed for green colored marbles, serpen- tine stones susceptible to warping and for any fiberglass mesh-backed tiles. 3.1.4.2 Suitable Backings . Acceptable substrates, when properly prepared and structurally sound, include con- crete, APA rated Exposure 1 underlay- ment grade plywood* , steel plate, and ceramic tile. Application is made in one thin layer. Pot life, adhesion, water cleanability before cure, and chemical resistance vary with manufacturer. 3.1.4.3 Installation and Material Specifications. Complete installa- tion and material specifications are contained in ANSI A108.6 and ANSI A118.3. 3.1.5 Limestone Setting Mortar. Cement used with limestone shall be white portland cement, ASTM C150, or white masonry cement, ASTM C91. Nonstaining cement shall contain not more than 0.03% of water-soluble alkali when determined in accordance with procedure 15, calculation 16 of ASTM C91 or Federal Specification SS-C181C. However, if a large amount of normal cement has been used in the backup material, and if an effective water barrier has not been provided between the stone and the backup, the use of nonstaining cement may not prevent all discoloration. Discoloration will disappear as the stone dries. The Indiana Limestone Institute recommends a 1:1:6 (portland:lime:sand) or Type N mortar be used with Indiana Limestone. At the present time, there are few mason- ry cement mortars produced labeled “nonstaining.” 3.1.6 Setting Bed. White portland cement with low alkali content is required for all light colored stone vari- eties. 3.2 Grouts Between Stones 3.2.1 Commercial Portland Cement Grout (“Unsanded Grout”) 3.2.1.1 Commercial portland cement grout is a mixture of portland cement and other ingredients, producing a 80 TileLetter | May 2018