When properly selected, installed, and maintained, ceramic tiles are one of the most durable of all materials used to finish pools and spas. Certain types of natural stone tiles may be used in these areas, but the stones must have the same properties exhibited by vitreous or impervious ceramic tiles. They must also be strong enough to withstand the normal brushing, chemicals, and maintenance necessary for a pool or spa environment.
TilesAbsorbent, non-vitreous tiles are frequently used in tropical climates, at the waterline, without much concern about freeze-thaw damage, and little thought about mold and mildew. But while non-vitreous tiles may be safe in non-freezing climates, they are porous enough to harbor mold and mildew. For that reason, I install only impervious porcelain tiles at, above, or below the waterline that meet the P1 requirements of ASTM C373 (see Photo 1). If the tiles are unglazed, I have little concern about wear, but if the tiles are glazed porcelain, it is important to select a glaze with a finish strong enough to withstand brushing, chemicals or salts, and the tough cleaning materials and methods that are sometimes required to keep the waterline free of encrusted salts and minerals that occasionally accumulate in pools, spas, and fountains. When tested according to ASTM C1027, Classes III, IV, or V are preferred. Class I or II glazed porcelain tiles are not recommended.
Chlorine and salts attack some metals and the resulting oxidation can cause discoloration. For best results when a metal tile is desired, choose stainless steel over brass, copper, or iron. Brass and copper oxides can stain grout blue and iron can turn white grout orange.
AdhesivesLatex is known for its ability to enhance dry set thinset mortars, however, not all latex or acrylic admixtures are suitable for submerged environments. Under the right conditions, and even after extensive curing, certain latex components can re-emulsify, soften, leech into the surrounding water, and cloud or contaminate it. Generally speaking, latex thinset mortars designed for pool, fountain, or spa use require a 28-day cure prior to immersion (see Photo 2). The same is true for most regular dry set thinset mortars approved for constant immersion.
All tiles installed above, at, or below a pool or spa’s waterline should have minimum 95% adhesive coverage to help eliminate voids and the potential to harbor mold or mildew. Of course, the role of most in-pool tiles is aesthetic, but some pool tiles are designed to enhance the safety of the people using it. The grip edge used to trim the edge of a pool’s coping is an example. To increase adhesion for the fat, 3/4-round grip-edge tiles shown in Photo 1, the manufacturer incised numerous cavities in the porcelain clay body, before firing, to ensure a tenacious grip regardless of what adhesive is used (Photo 3).
All-tile pools and spas are quite common, and they require a highly detailed network of movement joints that require periodic maintenance and replacement. I prefer to use tiles as accents with plaster as the main finishing material. To do this, I simply wait 28 days for the concrete tank to cure, clean off the surface, install tiles directly over the concrete tank with thinset mortar. And allow them to cure 28 days before plastering up to them. Since the plaster must be immersed completely in water on installation (Photo 5), the timing for curing the tiles is critical to the durability of the pool or spa.
When the pool shown in the photos was built, it required approximately 524,000 pounds of concrete; filling it required 48,000 gallons of water or another 400,000 pounds: A pool tends to move, expand, contract, and travel (sometimes) when it wants to and without regard to anything in its way. A half-inch wide movement joint allows the pool to move within reason, prevents damage to the deck stones or coping tiles, and is a requirement for all pools and tiled-in spas (Photo 7).
Standard Specifications for tile are available from the Tile Council of North America at: www.tileusa.com
Tiles courtesy: Michelle Griffoul Studios, www.michellegriffoul.com
Photos courtesy: Mike Mesikep