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CERAMIC TILE

LEARNING OBJECTIVE:

Upon completing this section, you should be able to identify the different types of ceramic tile and associated mortars, adhesives, and grouts, and state the procedures for setting tiles.

Ceramic tile is used extensively where sanitation, stain resistance, ease in cleaning, and low maintenance are desired. Ceramic tiles are commonly used for walls and floors in bathrooms, laundry rooms, showers, kitchens, laboratories, swimming pools, and locker rooms. The tremendous range of colors, patterns, and designs available in ceramic tile even includes three-dimensional sculptured tiles. Extensive use has been made of ceramic tile for decorative effects throughout buildings, both inside and outside.

CLASSIFICATIONS

Tile is usually classified by exposure (interior or exterior) and location (walls or floors), although many tiles may be used in all locations. Since exterior tile must be frostproof, the tiles are kiln fired to a point where they have a very low absorption. Tiles vary considerably in quality among manufacturers. This may affect their use in various exposures and locations.

SIZES

Tile is generally available in the following square sizes: 4 1/4 by 4 1/4, 6 by 6, 3 by 3, and 1 3/8 by

1 3/8 inches. Rectangular sizes available include 8 1/2 by 4 1/4, 6 by 4 1/4, and 1 3/8 by 4 1/4 inches. Tile often comes mounted into sheets (usually between 1 and

2 square feet) with some type of backing on the sheet or between the tiles to hold them together.

Tiles with less than 6 square inches of face area and about 1/4 inch thick are called ceramic mosaics. Ceramic mosaic tile sizes range from 3/8 by 3/8 inch to about 2 by 2 inches, and they are available from the manufactures in both sheet and roll form. Often, large tile is scored by the manufacturer to resemble small tiles.

FINISHES

Tile finishes include glazed, unglazed, textured (matte) glazed porcelain, and abrasive. Glazed and matte glazed finishes may be used for light-duty floors but should not be used in areas of heavy traffic where the glazed surface may be worn away. Glazed ceramic wall tiles usually have a natural clay body (nonvitreous, 7-to 9-percent absorption), and a vitreous glaze is fused to the face of the tile. This type of tile is not recommended for exterior use. Glazed tile should never be cleaned with acid, which mars the finish. Use only soap and water. Unglazed ceramic mosaics have dense, nonvitreous bodies uniformly distributed through the tile. Certain glazed mosaics are recommended for interior use only, others for wall use only. Porcelain tiles have a smoother surface than mosaics and are denser, with an impervious body of less than one-half of 1-percent absorption. This type of tile may be used throughout the interior and exterior of a building. An abrasive finish is available as an aggregate embedded in the surface or an irregular surface texture.

Tales are available with self-spacing lugs, square edges, and cushioned edges (slightly rounded) (see fig. 7-22). The lugs assure easy setting and uniform joints. The edges available vary with the size of the tile and the manufacturer.

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Figure 7-22.—Tile edges.

Margins, comers, and base lines are finished with trimmers of various shapes (fig. 7-23). A complete line of shaped ceramic trim is available from manufacturers. Other accessories include towel bars, shelf supports, paper holders, grab rails, soap holders, tumbler holders, and combination toothbrush and tumbler holders, to list a few of the more popular units.

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Figure 7-23.—Trimmer shapes.

MORTARS AND ADHESIVES

The resistance of ceramic tile to traffic depends primarily on base and bonding material rigidity, grout strength, hardness, and the accurate leveling and smoothness of the individual tiles in the installation. The four basic installation methods are cement mortar (the only thick bed method), dry-set mortar, epoxy mortar, and organic adhesives (mastic).

Cement Mortar

Cement mortar for setting ceramic tiles is composed of a mixture of portland cement and sand. The mix proportions for floors may vary from 1:3 to 1:6 by volume. For walls, a portland cement, sand, and hydrated lime mix may vary from 1:3:1 to 1:5 1/2:1. These proportion ratios are dictated by the project specifications. The mortar is placed on the surface 3/4 to 1 inch thick on walls and 3/4 inch to 1 1/4 inches thick on floors. A neat cement bond coat is applied over it while the cement mortar is fresh and plastic. After soaking in water for at least 30 minutes, the tiles are installed over the neat cement bond coat. This type of installation, with its thick mortar bed, permits wall and floor surfaces to be sloped. This installation provides a bond strength of 100 to 200 pounds per square inch. A waterproof backing is sometimes required, and the mortar must be damp-cured.

Dry-Set Mortar

Dry-set mortar is a thin-bed mortar of premixed portland cement, sand, and admixtures that control the setting (hardening) time of the mortar. It may be used over concrete, block, brick, cellular foamed glass, gypsum wallboard, and unpainted dry cement plaster, as well as other surfaces. A sealer coat is often required when the base is gypsum plaster. It is not recommended for use over wood or wood products. Dry-set mortar can be applied in one layer 3/32 inch thick, and it provides a bond strength of 500 pounds per square inch. This method has excellent water and impact resistance and may be used on exteriors. The tiles do not have to be presoaked, but the mortar must be damp-cured.

Epoxy Mortar

Epoxy mortar can be applied in a bed as thin as 1/8 inch. When the epoxy resin and hardener are mixed on the job, the resulting mixture hardens into an extremely strong, dense setting bed. Pot life, once the parts are mixed, is about 1 hour if the temperature is 82F or higher. This mortar has excellent resistance to the corrosive conditions often encountered in industrial and commercial installations. It may be applied over bases of wood, plywood, concrete, or masonry. This type of mortar is nonshrinking and nonporous. A bond strength of over 1,000 pounds per square inch is obtained with this installation method.

Organic Adhesives

Organic adhesives (mastics) are applied in a thin layer with a notched trowel. They are solvent-base, rubber material. Porous materials should be primed before mastic is applied to prevent some of the plasticizers and oils from soaking into the backing. Suitable surfaces include wood, concrete, masonry, gypsum wallboard, and plaster. The bond strength available varies considerably among manufacturers, but the average is about 100 pounds per square inch.

GROUTS

The joints between the tiles must be filled with a grout selected to meet the tile requirements and exposure. Tile grouts may be portland cement base, epoxy base, furans, or latex.

Cement grout consists of portland cement and admixtures. This is better in terms of waterproofing, uniform color, whiteness, shrink resistance, and fine texture than a plain cement. It maybe colored and used in all areas subject to ordinary use. When the grout is placed, the tiles should be wet. Moisture is required for proper curing.

Drywall grout has the same characteristics as dry-set mortar and is suitable for areas of ordinary use. Tiles to be set in drywall grout do not require wetting except during very dry conditions.

Epoxy grout consists of an epoxy resin and hardener. It produces a joint that is stainproof, resistant to chemicals, hard, smooth, impermeable, and easy to clean. It is used extensively in counters that must be kept sanitary for foods and chemicals. It has the same basic characteristics as epoxy mortars.

Furan resin grout is used in industrial areas requiring high resistance to acids and weak alkalies. Special installation techniques are required with this type of grouting.

Latex grout is used for a more flexible and less permeable finish than cement grout. It is made by introducing a latex additive into the Portland cement grout mix.

TOOLS

A selection of special tools, shown in figure 7-24, should be available when doing tile installation work.

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Figure 7-24.-Special tile-setting tools.

A primary tool is a notched trowel with the notches of the depth recommended by the adhesive manufacturers. A trowel with notches on one side and smooth on the other is preferred. Different sized trowels are available.

A tile cutter is the most efficient tool for cutting ceramic tile. The scribe on the cutter has a tungsten carbide tip. A glass cutter can be used but quickly dulls.

Use tile nippers when trimming irregular shapes. Nip off very small pieces of the tile you are cutting. Attempting to take big chunks at one time can crack the tile.

A rubber-surfaced trowel is used to force grout into the joints of the tile.

APPLICATION TECHNIQUES

There are three primary steps in tile installation: applying a mortar bed, applying adhesive, and setting tiles in place.

Mortar

Before applying a mortar bed to a wall having wooden studs, you first tack a layer of waterproof paper to the studs. You then nail metal lath over the paper. The first coat of mortar applied to a wall for setting tiles is a scratch coat; the second is a float, leveling, or brown coat.

A scratch coat for application as a foundation coat must be at least 1/4 inch thick and composed of 1 part cement to 3 parts sand, with the addition of 10-percent hydrated lime by volume of the cement used. While still plastic, the scratch coat is deeply scored or scratched and cross scratched. Keep the scratch coat protected and reasonably moist during the hydration period. All mortar for scratch and float coats should be used within 1 hour after mixing. Do not retemper partially hardened mortar. Apply the scratch coat not more than 48 hours, nor less than 24 hours, before setting the tile.

The float coat should be composed of 1 part cement, 1 part of hydrated lime, and 3 1/2 parts sand. It should be brought flush with screeds or temporary guide strips, placed to give a true and even surface at the proper distance from the finished face of the tile.

Wall tiles should be thoroughly soaked for a minimum of 30 minutes in clean water before being set. Set tiles by troweling a skim coat of neat Portland cement mortar on the float coat, or applying a skim coat to the back of each tile unit and immediately floating the tiles into place. Joints must be straight, level, perpendicular, of even width, and not exceeding 1/16 inch. Wainscots are built of full courses. These may

extend to a greater or lesser height, but in no case more than 1 1/2-inch from the specified or figured height. Vertical joints must be maintained plumb for the entire height of the tile work.

All joints in wall tile should be grouted full with a plastic mix of neat white cement or commercial tile grout immediately after a suitable area of the tile has been set. Tool the joints slightly concave; cut off and wipe excess mortar from the face of tiles. Any spaces, crevices, cracks, or depressions in the mortar joints after the grout has been cleaned from the surface should be roughened at once and filled to the line of the cushioned edge (if applicable) before the mortar begins to harden. Tile bases or coves should be solidly backed with mortar. Make all joints between wall tiles and plumbing or other built-up fixtures with a light-colored caulking compound. Immediately after the grout has set, apply a protective coat of noncorrosive soap or other approved protection to the tile wall surfaces.

The installation of wall tile over existing and patched or new plaster surfaces in an existing building is completed as previously described, except that an adhesive is used as the bonding agent. Where wall tile is to be installed in areas subject to intermittent or continual wetting, prime the wall areas with adhesive following the manufacturer’s recommendations.

Adhesive

Wall tiles may be installed either by floating or buttering the adhesive. In floating, apply the adhesive uniformly over the prepared wall surface using quantities recommended by the manufacturer. Use a notched trowel held at the proper angle to spread adhesive to the required uniform thickness. Touch up thin or bare spots with an additional coating of adhesive. The area coated atone time should not be any larger than that recommended by the manufacturer. In the buttering method, daub the adhesive on the back of each tile. Use enough so that, when compressed, the adhesive forms a coating not less than 1/1 6 inch thick over 60 percent of the back of each tile.

Laying Tile

The key to a professional-looking ceramic tile job is to start working with a squared-off area. Most rooms do not have perfectly square comers. As a result, the first step is to mark off a square area in such a way that fractional tiles at the comers (edges) are approximately the same size. Begin by finding the lowest point of the wall you are tiling. From this corner draw a horizontal line one full tile height above the low point and extend this line level across the entire width of the room. Refer to the bathroom wall example in figure 7-25 as you study the following steps:

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Figure 7-25.-Steps used for squaring a wall.

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Figure 7-26.-Layout for installing ceramic wall tile.

  • Find the low point of the tub.
  • Measure up the height of one full tile at the low point. Draw a horizontal line A. It must be level.
  • Use a tile-measuring stick (fig. 7-26) to determine the position of full-width tiles in such away that fractional tiles at each comer or edge are equal.
  • Draw vertical lines B and C perpendicular to line A (fig. 7-25). Apply tiles to the squared-off area first. Then cut and apply fractional tiles.

Another method for figuring fractional tiles (edges) is to employ the "half-tile rule." (The stick method is good for short walls, but the half-tile rule is needed for long walls.) Take the number of full-size tiles required for one course, multiply this by the tile size, subtract this answer from the wall length in inches, add one full tile size and divide by 2. The result is the size of end tiles.

After determining fractional tiles, use a piece of scrap wood from 36 inches to 48 inches in length to mark up a tile-measuring stick (fig. 7-26, view A). Mark off a series of lines equal to the width of a tile. Lay this stick on the wall and shift it back and forth to determine the starting point for laying the tiles. Make sure the fractional tiles at the end of each row are of equal widths (fig. 7-26, view B).

Use a level to establish a line perpendicular to the horizontal starting line (fig. 7-26, view C). At both ends of the horizontal line, draw vertical lines to form the squared-off area. To make the tile application easier, you can fasten battens to the wall on the outside of the drawn lines.

Use a trowel to spread the mastic over approximately a 3- by 3-foot area of the wall. Use the notched side to form ridges in the mastic, pressing hard against the surface so that the ridges are the same height as the notches on the tool. Allow the mastic to set for 24 hours before applying grout. Follow the manufacturer’s mixing instructions closely and use a rubber-surfaced trowel to spread the grout over the tile surface. Work the trowel in an arc, holding it at a slight angle so that grout is forced into the spaces between the tiles.

Start tiling at either of the vertical lines and tile half the wall at a time, working in horizontal rows. Press each tile into the mastic, but do not slide them—the mastic may be forced up the edges onto the tile surface. After each course of tile is applied, check with the level before spreading more mastic. If a line is crooked, remove all tiles in that line and apply fresh ones. Do not use the removed tiles until the mastic has been cleaned off. Finish tiling the main area before fitting edge tiles.

When the grout begins to dry, wipe the excess from the tiles with a damp rag. After the grout is thoroughly dry, rinse the wall and wipe it with a clean towel.

Nonstaining caulking compound should be used at all joints between built-in fixtures and tile work and at the top of ceramic tile bases to ensure complete waterproofing. Inside corners should be caulked before a comer bead is applied.

Promptly replace cracked and broken tiles. This protects the edges of adjacent tiles and helps maintain waterproofing and appearance. Timely pointing of displaced joint material and spalled areas in joints is necessary to keep tiles in place.

A new tile surface should be cleaned according to the tile manufacturer’s recommendations to avoid damage to the glazed surfaces.

 

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