Surface treatment: the basics of ceramic tile
Although it is well known that kitchens and baths sell a house, exterior roomscapes and the lifestyle they suggest are emerging as the new must-haves. For many home buyers, the perfect dream property now includes terraced seating areas, private decks, and furnished outdoor living rooms; transitional courtyards and garden paths that blur the line between indoor and outdoor living quarters; alfresco dining rooms under vine-covered pergolas where a state-of-the-art grill and fire pit vie for attention with fountains, koi ponds, spas, and swimming pools.
As much energy and expense is going into the design of these outdoor rooms as is spent on their interior counterparts. Sophisticated design and top-quality materials normally associated with interior decor have replaced the picnic table and bare bones look of the ’80’s. Cushions, candelabras, artwork, and antiques grace these rooms under the stars. Following this trend, material choices for exterior floors and walls have been dramatically upgraded.
For these reasons, ceramic the has become a mainstay in landscape and outdoor room design. Flowing through the main areas of the house and spilling onto patios and terraces, ceramic tile creates the unifying thread that winds through the various rooms of the garden and integrates the indoors and out. Tiles in rich terra-cotta, soft tumbled-stone finishes, or hand-painted fresco tiles reinforce a vacation-like Mediterranean theme and complement the rich hues of nature. In fact, ceramic tile can deliver a virtually limitless array of styles, sizes, patterns, colors, and functional utility. Tile surfaces are easily cleaned, hygienic, heat resistant, colorfast in sunlight, slip resistant, and long lasting.
The key to a successful tile installation begins with specing the right tile to withstand the rigors of outside use. In regions where frost is not an issue, almost any ceramic tile can be considered for exterior use. However, for locations subjected to freezing weather, you must ensure the frost resistance of the tile you choose. Quality manufacturers supply a single-page data sheet on every tile they produce. An international standard is used to confirm frost resistance for all tile imported into the United States and an ASTM designation is used for tile produced in North America. Although it might sound like an oversimplification, the reality is that if a tile is not listed as “passed” or “resistant” under one of the following standards, it is highly questionable if the tile will perform to expectations in any geographical area that has freezing weather.
* EN 202 Passed. Tile is chilled to -5 degrees C (-23 F) and then rapidly heated to 5 degrees C (41 F). Tile must survive 50 freeze/thaw cycles.
* ISO 10545-12 Passed. Identical test to EN 202 with tile subjected to 100 freeze/thaw cycles.
* ASTM C1026 Resistant. Tile is chilled to -18 degrees C (-40 F) and then rapidly heated to between 10 to 16 degrees C (50-60 F). Tile must survive 15 cycles of freeze/thaw.
When a manufacture engineers a tile intended and warranted for outside applications, the tile is always tested for frost resistance. All frost-resistant tiles will also be designed for relatively low water absorption. The water absorption percentage (WA%) of each tile is clearly listed on the tile data sheet and can be used to further define where each tile can be used successfully.
* Water Absorption Range O% to .5%. Look for tile in this low absorption range for any applications that will be submerged in water, constantly saturated, or soaked. These areas include shower floors, inside swimming pools at the water line, stairs or any area under water, inside fountains, and pool coping.
* Water Absorption Range Greater Than .5% to 3%. Tile in this range can be used for any area subjected to intermittent or occasional water exposure, such as rain. Areas include shower walls or any vertical installations, countertops, decks, and balconies (all properly sloped for water evacuation).
* Water Absorption Range Higher Than 3%. Tile that has absorption above 3% is not normally tested or recommended for exterior applications. However, some extruded paver tile with WA above 3% is specifically made for exterior use and easily passes the frost-resistant standard. Conversely, some porcelain tile with WA listed at .5% may be engineered for interior use only. It will not be tested or approved by the manufacturer for exterior applications.
Glazed or Not
Exterior tile programs can be found in both glazed and unglazed formats. Each type of finish has features and benefits that should be matched to the homeowners’ lifestyle requirements, maintenance expectations, safety issues, aesthetics, and expected type of traffic.
Glazing on the tile surface greatly expands available colors, patterns, and textures. Applying several colors and patterns on the surface of the tile through screening technology is the most versatile way to change the monochromatic color and finish of clay. As well as being aesthetic, the glaze layer completely seals the upper surface of the ceramic body, providing the highest level of stain resistance. Glazed tiles me therefore the easiest to maintain and do not require sealing of any kind. Glazed tiles may have a textured surface or use gritty mineral particles in the glaze to enhance slip resistance. A potential drawback for glazed tile will be in locations where sharp sand, sea salt, or gritty dirt will be constantly ground into the surface of the tile. In that case, premature wear on the surface glaze will he unavoidable unless the surface soil is cleaned from the tile regularly. A glazed tile will also reveal the clay body color when chipped, detracting from its aesthetic and functional quality. This may be a concern in areas where snow will be shoveled.
Almost all unglazed tile rated for exterior use will be in the “impervious” range or have water absorption equal to or less than .5%. It is commonly called porcelain tile and can be compared to natural stone and should be treated and used in the same locations and for identical purposes. In fact, most unglazed impervious tiles are mechanically much stronger than natural stone, including granite. The unglazed tile will provide the user with the highest level of abrasion resistance from heavy wear and abrasive contaminants. And, because the surface color and pattern is carried through the entire dimensional thickness of the tile, chipping will not change the tile’s color. Like natural stone, unglazed tile may or may not require sealing to prevent stains from penetrating the surface. But unlike natural stone, all unglazed impervious tile has consistently reliable porosity. Many natural stones have much higher porosity levels or natural inconsistencies and fissures across the surface. Any unglazed tile with porosity above .5%, such as pavers, gres tile, and terra cottas, usually require sealing to prevent staining.
Factors other than tile selection can lead to problems with exterior tiling. Most installations will be exposed to water, so preparation of all horizontal surfaces must incorporate a slope. The critical factor in these applications is to ensure a way for water to dram and evaporate from the system. A slope of 1/4 inch per foot is required to provide complete surface drainage. In tiled areas where a waterproof membrane is required, the membrane must be sloped. It is also preferable to mount railings on the fascia or other vertical architectural elements rather than penetrating through the membrane and compromising its watertight integrity.
Once the tile has been selected and the substrate properly sloped for tile, the next crucial detail is installation technique. Exterior filing must have a minimum 95% adhesion of the mortar to the back of the tile. When tile is completely submerged, optimal coverage on the back of the tile is 100%. For this reason, some mosaic tile traditionally used in pool and spa construction will be mounted at the factory with a layer of paper adhered to the face of the tile. This ensures 100% of the tile back will be in contact with the bonding mortar. However, back-mounted mosaics using mesh or dot mounting are more common, and experienced installers will back-butter the sheets to ensure proper bonding and support of the tile.
The rigidity and permanence of tile must be respected when detailing an exterior tile project. Although thermal expansion and contraction happens in all materials both inside and out, the continuous change in dimension of a tiled surface is particularly unforgiving. Failures occur simply because the pressures exerted on the tile are either not allowed for or are substantially underestimated. Including suitable expansion joints throughout the field of tile allows the tile to push against flexible caulking material rather than hard cement grout. The elastic nature of a caulked joint stretches and contracts in response to the tile, preventing buckling, cracking, and delamination of the tile from the substrate. Creating grids of no larger than 12 feet by 12 feet separated by a minimum 3/8-inch flexible joint is recommended for all exterior tiling. Color-matched caulking now available from manufacturers allows for next-to-invisible integration of this requirement. Adhering to the complete recommendations of the Tile Council of America’s ceramic installation handbook regarding expansion joints would virtually eliminate cracked tile and grout.
The impact of extreme climatic conditions or dramatic fluctuations in temperature can be deceiving. Excessive thermal movement can happen on expanses of wall tile as well as floor or paving areas, especially if the tile is a dark color or if the wall has full southern exposure. A dark-colored tile will absorb more energy from the sun and dramatically increase the temperature of the wall, creating expansion pressure. Choosing a smaller tile, increasing the number of expansion joints, or selecting a tile with a lower absorption rating will mitigate the effects of extreme climate changes and tile color.
Ceramic tile has lasted for centuries on facades and paving areas throughout the world. When tile is selected and installed correctly, it protects and beautifies any surface it covers. Tile’s variety, style, and endless color selection have guaranteed its place as a high-fashion finish material. In response to the growing trend in residential landscape design, manufacturers are pushing beyond fashion to enhance the technical value of tile. “Smart” tile currently in development will incorporate interactive devices such as motion detectors for alarm and security. Innovative glaze and texturing formulas are now available that provide a highly slip-resistant tile in wet conditions while remaining smooth and easily cleanable when the tile is dry. Sophisticated random screening techniques are creating tile programs with as much variation in color, texture, and veining as natural stone. The evolution of modern home design will continue to respond to the needs of the 21st century family. Ceramic tile will continue to fulfill the dreams and anticipate the needs of the homeowner–working equally well both inside the home and in the garden. * Patti Fasan is an expert on ceramic tile arm a consultant to the ceramic tile industry.
Patti Fasan is an expert on ceramic tile arm a consultant to the ceramic tile industry.
COPYRIGHT 2004 Hanley-Wood, Inc.
COPYRIGHT 2004 Gale Group