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There always remains a risk that the potential seal and adhesion of grout to tile edge offers gaps. Do not rely on tile
or setting material to function as a way of water or water vapor proofing. It remains, however, best practice and is
important, to choose a most fitting combination of setting materials and surface finish systems that are made to endure
in submerged and water vapor exposed, high temperature and abrupt temperature change environment and work
with each other in this climate. A best practice for the choice of surface finish or tile includes choosing rectified, dense
tile with lowest absorption rates (ANSI 137.1 rated for <.5% vol. absorption) and as large in size as possible. Rectified
and large in size helps minimizing grout line exposure surface as well as it helps to align grout lines for a tightly packed
fill. On the other end of the scale, Natural Stone is not recommended for use in a steam room. For safety in a wet area,
the tile for the floor or stadium seating benches should provide the adequate coefficient of friction (0.42).
Adhesives and grout must also withstand the exposure the elements and climate, as well as aggressive cleaning and
cleaning materials over time. They must remain unaffected in their adhesion qualities to substrate and tile, and not
produce reactions such as efflorescence, which is a common side effect with cement based materials, when constantly
exposed to water or water vapor pressure. Water moving through the construction layers may take on soluble salts and
may deposit them when surfacing. Efflorescence is mostly known as a cosmetic issue as it causes such discolorations
and deposit residues on surfaces. But it may develop into a functional issue. Trapped or continuously present sub-tile
moisture expands when heated or continuously entering below the tile as vapor, applying stress to adhesive systems.
Salts can also crystallize within the adhesive line, causing break down of the adhesive.
Many epoxy based bond mortars and grouts (ANSI 118.3), often also available as one product used for both setting
and grouting the tile, have a good potential to help minimizing vapor migration into grout lines and between tile and
setting bed surfaces over tile underlayment / vapor or waterproofing layers. They also have good potential to retain
their bond strength over time but must be recommended for use in higher temperatures. They will not contribute to
efflorescence and withstand aggressive cleaning better than most cement based setting materials. One disadvantage
is the lack of flexibility which is natural to epoxy based materials. This might present an issue where tile is chosen that
will expand and contract at higher rates in the steam room environment.
A better alternative to epoxy might be found within the range of setting mortars classified under ANSI 118.15. These
thinset mortars are developed to work with tiles we particularly favor in steam rooms, including large format tile and
glass tile. They are developed to endure under submerged applications and offer flexibility as most modified mortars
do. They should be used in combination with solid epoxy grouts, however.
No matter the choice of tile and setting material, wedi recommends the use of expansion joints in all tile surfaces. The
placement should be at perimeters and corners, where planes generally change, and every 8 ft. in either direction in
large surface areas. Materials used for theses joints must be fit for use in steam rooms. Many sealants may not handle
the moisture / submersion, heat well.
The TCNA also stresses the proper design of steam rooms including placement expansion joints in tile, see Details EJ171
(refer to exterior application type as being most close to the application of stream rooms in terms of extreme exposure
levels) for more details such as width and materials recommendations. When installing tile in steam rooms, please ensure
all best practices for setting techniques and goals as outlined in the TCNA handbook are followed. The same is true with
tile and setting materials’ manufacturer recommendations. Of particular importance is that a coverage of between 95 and
100% of thinset and high bond strength between immediate substrate and back of the tile are achieved.
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