MATERIALS FOR SETTING CERAMIC TILE

Introduction:
The following are the most widely used materials for setting ceramic tile. Each possesses specific qualities that make it suitable for installing tile over certain backings or under a given set of conditions.

The conventional portland cement mortar method, including the one-coat method, is the only recognized thickbed method. All others are thin-bed methods and are covered by existing trade jurisdictional decisions of record. Dry-set mortars and latex-portland cement mortars can be used in lieu of neat cement as a 1/16"-thick bond coat to bond ceramic tile to a Portland cement mortar bed that is still workable. They can also be used on a cured portland cement mortar bed (minimum 3/32" thickness after beat-in) according to ANSI A108.1B. A neat cement bond coat can be used only when the portland cement mortar is still workable (A108.1A). Absorptive ceramic tile must be soaked before setting on a mortar bed that is still workable when using a neat portland cement bond coat. Under normal job conditions, a minimum of 20 hours cure at 70°F is adequate, but longer mortar bed cures of up to 10 days are desirable. When epoxy mortars, epoxy adhesives, furan, or organic adhesives are used, the mortar bed must be dry.

To insure practical and satisfactory installations, the cement mortar bed to receive the tile, whether left workable or allowed to harden, is to be applied by the tile contractor who must establish all the finished dimensions at the time this bed is applied.

Non-cement setting materials such as epoxies and furans offer properties not possible with cement-based mortar; e.g., chemical resistance, quick setting times. However, special skills on the part of the tile setter are required. The cost of these materials can be appreciably greater than cement-based mortars.

Portland Cement Mortar:

A mixture of portland cement and sand, roughly in proportions of 1:5 for floors; and of portland cement, sand, and lime, in proportions of 1:5:1/2 to 1:7:1 for walls.

Portland cement mortar is suitable for most surfaces and ordinary types of installation. A mortar bed, up to 2" in thickness, facilitates accurate slopes or planes in the finished tilework on floors and walls.

The mortar bed can be modified with the inclusion of a latex polymer per the manufacturer's directions as part or all of the liquid portion of the mixture to enhance certain performance properties.

There are two equivalent methods recognized for installing ceramic tile with a portland cement mortar bed on walls, ceilings, and floors. They are: (1) the method covered by ANSI A108.1A, which requires that the tile be set on a mortar bed that is still workable, and (2) the method covered by ANSI A108.1B, which requires that the tile be set on a cured mortar bed with dry-set or latexportland cement mortar. Absorptive ceramic tile must be soaked before setting on a mortar bed that is still workable when using a neat portland cement bond coat.

Portland cement mortars can be: bonded to concrete floors; backed with membranes and reinforced with wire mesh or metal lath; or applied on metal lath over open studding on walls. They are structurally strong, are not affected by prolonged contact with water, and can be used to plumb and square surfaces installed by others.

Suitable backings, when properly prepared are: brick or cement masonry, concrete, wood or steel stud frame, rough wood floors, plywood floors, foam insulation board, gypsum board, and gypsum plaster. The one-coat method may be used over masonry, plaster, or other solid backing that provides firm anchorage for metal lath. Complete installation and material specifications are contained in ANSI A108.1A, A108.1B, and A108.1C.

Dry-Set Mortar:

A mixture of portland cement with sand and additives imparting water retentivity which is used as a bond coat for setting tile.

Dry-set mortar is suitable for thin-set installations of ceramic tile over a variety of surfaces. It is used in one layer, as thin as 3/32" after tile are beat in, has excellent water and impact resistance, is water-cleanable, non-flammable, good for exterior work, and does not require soaking of tile.

Dry-set mortar is available as a factorysanded mortar to which only water need be added. Cured dry-set mortar is not affected by prolonged contact with water, but does not form a water barrier. It is not a setting bed and is not intended to be used in truing or leveling the work of others.

Suitable backings, when properly prepared, include plumb and true masonry, concrete, gypsum board, cementitious backer units, cured portland cement mortar beds, brick, ceramic tile, and dimension stone. Complete installation and material specifications are contained in ANSI A108.5 and ANSI A118.1.

Note: The term "thin-set" is used to describe the method of installing tile with a bonding material usually 3/32" to 1/8" in thickness. In certain geographical areas, the term thin-set may be used interchangeably for "dry-set" portland cement mortar.

Latex-Portland Cement Mortar:

A mixture of portland cement, sand, and special latex additive which is used as a bond coat for setting tile.

The uses of latex-portland cement mortar are similar to those of dry-set mortar. Latex additives for use in thin-set portland cement tile setting mortars are designed to improve adhesion, reduce water absorption, and provide greater bond strength and resistance to shock and impact. These additives allow some latitude in time, working conditions, and temperatures. Therefore, latex-portland cement mortar is required for the installation of large-unit porcelain-bodied tile.

When latex-portland cement mortar is used to install ceramic tile in an area that may not thoroughly dry out in use (e.g., swimming pools and gang showers, etc.), it is recommended that the completed installation be allowed to dry out thoroughly before exposure to water. This drying period can fluctuate from 14 to over 60 days depending upon the geographical location, the climatic conditions, and whether the installation is interior or exterior. Since latices vary considerably, the directions of the latex manufacturer must be followed explicitly.

Complete installation and material specifications are contained in ANSI A108.5 and ANSI A118.4.

EGP (Exterior Glue Plywood) Latex Portland Cement Mortar:

A modified portland cement dry-set mortar to which a polymer has been incorporated in latex form or in a powder form for the bonding of ceramic tile to exterior glue plywood in interior dry or limited water exposure areas only. When added in latex form it is added as a replacement for part or all of the gauging water in accordance with the manufacturer’s instructions.

Complete installation and material specifications are contained in ANSI A108.12 and ANSI A118.11.

Epoxy Mortar:

A mortar system designed for chemical resistance employing epoxy resin and epoxy hardener portions.

Epoxy mortar is suitable for thin-set installations of ceramic tile where chemical resistance of floors, high bond strength, and high impact resistance are important considerations. High-temperature-resistant formulas are also available. Acceptable sub-floors, when properly prepared, include concrete, wood and 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.

Complete installation and material specifications are contained in ANSI A108.6 and ANSI A118.3.

Epoxy grout is also available. See section on grouts.

Modified Epoxy Emulsion Mortars:

A mortar system employing emulsified epoxy resins and hardeners with portland cement and silica sand.

Modified epoxy emulsion mortars are formulated for thin-set installations of ceramic tile on floors and walls, interior and exterior. Their features include high bond strength, ease of application, little or no shrinkage, and economical epoxy application. They are not designed for chemical resistance.

Recommended uses include residential floors, over substrates such as cementitious backer units and concrete. Where complete and firm support under the tiles is mandatory, 95% coverage is required. This material is recommended by most manufacturers as a bond coat or setting material. Some also recommend it for grouting.

Complete installation and material specifications are contained in ANSI A108.9 and ANSI A118.8.

Furan Resin Mortar:

A mortar system designed for chemical resistance consisting of furan resin and furan hardener portions.

Furan mortar is suitable for thin-set installations of ceramic tile where chemical resistance of floors is an important consideration. Acceptable sub-floors, when properly prepared, include concrete, wood and plywood, steel plate, and ceramic tile.

Complete installation and material specifications are contained in ANSI lA108.8 and ANSI A118.5. Furan grouts are also available. See section on grouts.

Epoxy Adhesive:

An adhesive system employing epoxy resin and epoxy hardener portions.

Epoxy adhesive is formulated for thinsetting of tile on floors, walls, and counters. It is designed primarily for high bond strength and ease of application and not for optimum chemical resistance. However, its chemical and solvent resistance tends to be better than that of organic adhesives.

Complete installation and material specifications are contained in ANSI A108.4 and ANSI A118.3.