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Failed bond between tile and setting compound over concrete (C) Daniel Friedman Guide to Ceramic Floor Tile Setting Compounds

A guide to ceramic & stone floor tile setting compounds:

This article discusses setting compounds used to install ceramic, stone, and similar floor tiles. We discuss organic mastics, dry-set mortar, polymer modified mortar, and modified expoxy or expoxy adhesives and mortars.

We address the installation details for each tile types. This article series discusses current best design practices for kitchens and bathrooms, including layout, clearances, work space, and accessible kitchen and bathroom layout, clearances, turning space, grab bars, controls, etc.

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Ceramic & Stone Floor Tile Setting Compounds Selection Guide

Ceramic tile floor set in thin-set mortar © D Friedman at InspectApedia.com

[Click to enlarge any image]

We include advice on choosing and installing kitchen countertops, cabinets, and kitchen or bathroom flooring, sinks, and other plumbing fixtures and fixture controls such as faucets. A list of kitchen and bath product manufacturers and sources is included.

This article includes excerpts or adaptations from Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) , by Steven Bliss, courtesy of Wiley & Sons.

Our photo (left) illustrates a bath restoration in an 1860's home, performed by the editor in the 1980s. Because the original wood flooring was badly deteriorated we installed 3/4-inch solid core plywood and then set these tiles in thin-set tile bedding compound.

Manufacturers offer a wide range of setting compounds formulated for different setting beds and conditions. Choosing the wrong one can result in a failed tile job.

For example, applications subject to moisture, temperature extremes, and heavy loading will need a higher quality setting compound than a kitchen backsplash, where organic mastic may serve perfectly well.

If applying mortar to a thickness of over 1/4 inch to even out low spots in the floor or irregularities in the tile, use a medium-set mortar or multipurpose thinset suited to the task. With any product, it is important to follow the manufacturer’s instructions regarding application and compatibility with the particular substrate (see Table 6-7).

[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]

Table 6-7: Ceramic Tile Setting Compound Guide (C) J Wiley S Bliss

Organic Mastics Used for Floor Tiles

These are ready-to-use adhesives primarily used with drywall and plywood substrates, although some are also approved for concrete and cement backerboards. Most now use a water-soluble formula, although some still use petroleum-based solvents.

In general, mastics are the least expensive setting material and provide the least strength and flexibility. The substrate must be very flat, since mastic is troweled on thin and cannot bridge low spots or uneven joints. Mastic should be avoided in applications subject to high temperatures.

Type II mastic is rated for use on walls not subject to wetting. Type I is approved for use on floors and wet areas. However, thinset mortars are better suited for floors and wet applications, for a modest increase in cost.

Dry-Set Mortar Use for Floor Tiles

Dry set mortar for floor tile installation is a factory blend of sand, cement, retarders, and other additives that is mixed with water on the job site. It provides a strong bond and high compressive strength, making it more suitable on floors than organic mastic. It is commonly used over concrete slabs, mortar beds, or cement backerboards. It cleans easily with water; but once dried, it is unaffected by water.

Polymer-Modified Mortar Uses for Floor Tile Installation

Polymer modified mortar for floor tiles is essentially dry-set mortar with latex or acrylic polymers added to increase the bond strength, compressive strength, and flexibility of the compound. One formulation uses a latex or acrylic liquid added to the dry mix at the job site.

The other has dry polymers blended into the dry mix at the factory so only water is added on site. Polymer-modified mortar bonds well to most substrates, including waterproofing membranes, to provide a premium waterproof system. Some kinds are not recommended for use with plywood, however (always check the label for compatibility with a substrate).

Cleanup should be done quickly with a damp sponge while the material is wet, or it is difficult to remove from skin and materials.

Modified-Epoxy Mortar and Grout System for Floor Tile Installation

Epoxy mortar for flooring is generally used for floors and countertops that require moderate chemical resistance, or where higher bond strength is needed to withstand greater loading, impacts, and flexing. It is also useful with questionable substrates such as existing tile, sheet vinyl, or plastic laminate, all of which are suitable for epoxy as long as they are sound and the surfaces are roughed up.

In addition to their higher cost, these products have precise mixing requirements, a short pot life, and more difficult cleanup than standard thinsets. High-chemical-resistance formulations are also available. Cleanup of dried material requires special solvents, and the silica sand presents a respiratory hazard. Because of the mixing requirements and faster setup, skilled applicators are required.

Epoxy Adhesive & Grout Floor Tile Details

Epoxy adhesive is often used to install green (serpentine), white, and other moisture sensitive marbles and marble agglomerates that may stain or warp with water-based products. It provides high-bond strength and impact-resistance over most sound substrates, including plywood.

It also provides water-resistance and moderate chemical-resistance. It requires precise mixing and skilled application, and special solvents are required to remove any material that dries on the surface of the tile (or the installer’s hands). Also, the silica sand presents a respiratory hazard.

Guide to Tile Installation with Thinset Mortars

Thinset Application

All mastics and thinset mortars are applied in the same way. First apply a thin layer of the adhesive using the flat edge of the trowel for continuous coverage, then comb with the notched edge of the trowel to create a uniform, flat setting bed. Hold the trowel at about 30 degrees from the surface for the continuous layer and at about 45 degrees when combing with the notched edge (Figure 6-39 shown below).

Figure 6-36: Ceramic Tile Setting Compound Guide (C) J Wiley S Bliss

Figure 6-39

[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]

Notches range from about 3/16 inch for thin tile to 3/8 inch for tiles 12x12 inches and larger or irregular tiles such as handmade pavers.

A 1/4 -inch notch works for most other tiles. Always follow the directions on the can. Coverage varies depending on the type of substrate and tile, as well as the heat and humidity in the environment. this is particularly important with tile 12x12 inches or larger.

Also apply thinset mortar to only one small section at a time—no larger than the area that can be tiled before the thinset skins over. Any thinset that skins over will have to be discarded.

Medium-Set Application for Tiles

Where irregularities in the substrate or tile shape, such as handmade pavers, require a setting bead thicker than 1/4 inch, choose a medium-set mortar or an all-purpose thinset approved for medium-set usage. Other thinset mortars are not strong enough when built up to that depth. Irregular-shaped tiles will need some adhesive “back buttered” directly to the tile to obtain proper coverage.

Tile Installation Using Thinset and Medium Set Mortars

Next press and twist in a sample tile to check the adhesive coverage. ANSI standards require that dry interior tiles be evenly covered over at least 80% of their surface area (Figure 6-39b).

Figure 6-36: Ceramic Tile Setting Compound Guide (C) J Wiley S Bliss

Figure 6-39 part b

[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]>

Wet or exterior applications require 95% coverage. When set back in place and beat in with a rubber mallet (larger tiles) or beating block (smaller tiles such as mosaics), the setting bed should be about 3/32 inch but not larger than 1/4 inch, unless medium-set mortar is used. Irregular-shaped handmade tiles need some adhesive “back buttered” directly to the tile to obtain proper coverage.

Also see flooring basics at

FLOOR DESIGNS: KITCHEN & BATH and

see CERAMIC TILE FLOOR & WALL

Ceramic Tile-Setting Material Manufacturer List

  • Ceramic Tile Backerboard Producers

  • Kitchen & Bath Industry Associations

    • -- Adapted with permission from Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) .

     


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