Photo 1: The
mosaic and feature tiles used to decorate and protect at, above, and below the
waterline of this spa and pool are glazed impervious porcelain.
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.
Photo 2: The
tiles at the waterline, and those attached to the concrete tank, were installed
more than 28 days before the plaster work shown here was completed.
As
well, tiles installed on the coping or walkways surrounding a pool or spa must
not be too slippery. Careful selection should also extend to the adhesives,
grouts, and sealants used around pools and spas: as in tiles, some installation
materials are preferred and some should be avoided. The main issues are the
rate of absorption of all materials used for the installation, the submerged
strength of the adhesives and grouts, and the toughness of the surface of the
tiles.
Tiles
Photo 3: Cavities
incised into the back of this grip-edge tile improves the bond strength between
the tile and the pool’s cast mortar coping.
Absorbent,
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.
Photo 4: Applicator
cleaning plaster residue from the surface of a tile. The tiles and their beds
of thinset mortar are a bit less than 1/2-inch – about the thickness of the
finishing layer of plaster.
Bond strength is definitely an
issue in a wet or submerged environment, and a concern with some types of tile
made from metal or glass: glass tiles with a back-coating are particularly
difficult to bond under any conditions, and may be impossible to bond in a pool
or spa. If glass tiles are desired, I prefer uncoated, face-mounted glass
mosaics, and follow ANSI A108.14, A108.15, or A108.16.
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.
Adhesives
Photo 5: Timing
is critical for the installation of the plaster, which must be cured by filling
the pool: All tiles must be cured a minimum 28 days prior to the day of
plastering.
Latex 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).
Photo 6: This
view shows the grip-edge tiles installed, the coping tiles staged to the right,
and a movement joint running right up the middle.
Probably more important than the
type of thinset mortar you use is the time that must be allowed for whatever
thinset mortar is used to cure properly. Curing cannot take place without
water, but subjecting many thinsets to total immersion usually results in a
reduction of bond, shear, and compressive strength. Under extreme conditions,
some thinset mortars can actually re-emulsify when subject to premature
immersion. For the installation contractor, timing is a critical factor in all
pool, spa, or fountain installations. No tiles should be installed over a concrete
tank or base until the concrete has cured a minimum of 28 days, and no tiles,
adhesives, or grouts should be subject to total immersion until 28-days after
the last tiling material has been installed (Photo 4).
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.
Photo 7: A
network of movement joints between the pool and spa and the surrounding stone
deck ensures long life for this installation.
Normally, the last job is to
install the tiles covering the pool coping. In Photo 6, the
grip-edge tiles have all been installed, and the remaining coping tiles have
been staged. At the center of the photo is a movement joint between the pool’s
tank and the surrounding sloped deck covered with irregular stone. Throughout
the year, even in stable tropical climates, a pool will move independently of
its surroundings.
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).
Resources:
Standard
Specifications for tile are available from the Tile Council of North America
at: www.tileusa.com
MichaelByrne www.michaelbyrne.us Michael
Byrne has been a tile installer since 1968 working on residential, commercial,
industrial, artistic and specialty installations. He is the author of two books, numerous videos and hundreds of
articles on tile installation. Michael has worked as an independent consultant
on installations in North, Central and South America, the UK and Europe, and is
one of the founders and was the first president and executive director of the
Ceramic Tile Education Foundation (CTEF). Michael is the owner of a consulting,
expert witness, and publishing company in Los Olivos, CA.
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