Tile for Architects, Designers & Affiliates

Steam room construction

Steam room construction

Jun 4, 2012

By Tom D. Lynch, CSI, NTCA Recognized Industry Consultant and author of TCNA Method SR614

QUALICER World Congress on Ceramic Tile Quality is a bi-annual symposium held in Castellón, Spain which began in the year 1990. Ceramic tile experts from around the world submit topics for lectures and open papers for presentations at each event. For QUALICER 92, my open paper titled “Steam Room Construction” was selected for presentation. In 1995 the Tile Council of America included this installation method in that year’s Handbook for Ceramic Tile Installation as “SR614-95 Thin-bed Steam Rooms.” With only slight modifications and updates in materials options added through the years, SR614 remains the most viable installation method for constructing steam rooms today. Perhaps the most appealing feature of SR614 is that tiles can be thin-set applied over a structure that is framed with either wood or steel studs. Steam rooms are highly specialized applications so precise design and installation methods beyond the framing stage are critical. Key components of the SR614 system will be highlighted in this discussion.

Reference Method in the 2011 or 2012 TCNA Handbook for Ceramic, Glass and Stone Tile Installation. The Method can be purchased online for $.99 at this link: http://www.tcnatile.com/products-and-services/publications/90-handbook-methods-and-guides/310-method-sr614steam-showerroom-woodmetal-studs-wood-or-metal-studsmortar-bed-or-cement-backer-board-wallsmortar-bed-floor.html.

Key Component #1: Substrates 

Cement backer boards as per ANSI A118.9 are the preferred substrate materials for the walls and ceiling. Fasteners are to be noncorrosive and non-oxidizing screws spaced as per the backer board manufacturer’s recommendations. The floors must be a wire-reinforced mortar bed with a sloped fill under the waterproofed shower pan. The sloped fill is critical to prevent the mortar bed from eventually becoming saturated with water which could cause deterioration to the point of failure.

Key Component #2: Waterproof Membrane

After the backer boards have been installed, all surfaces are to receive a continuous layer of waterproofing material. Waterproofing can be either sheet or liquid applied. Waterproof membrane must meet ANSI A118.10 standards. The shower pan (floor waterproofing) must either tie in to the waterproofing at the walls or extend up a minimum of 6” above the floor and behind the cement board. Some design professionals prefer incorporating both.

Key Component #3: Control Joints, Sealants

Nothing has more frequent and pronounced changes in ambient air temperatures than a well-used steam room. It is imperative, therefore, to provide maximum controls for expansion and contraction of the entire system. All control joints must extend through the substrates. Slip joints are needed at all interfaces of floor/wall and ceiling/wall locations. All membrane penetrations for plumbing, light fixtures, fasteners, etc. must be sealed to prevent moisture penetration. Sealants must be either urethane or silicone as recommended by the manufacturer.

Key Component #4: Pitches and Slopes

The standard slope for ceramic tile floors in wet areas is 1/4” per foot, but I suggest doubling that for the sloped fill as well as the mortar bed.  It is important to move water as fast as possible to the drains on top of the tile as well as to the weep holes in the drain at the underside of the mortar bed. The ceiling needs to be sloped a minimum of 2” per foot so that condensate flows to the walls rather than dripping on to the occupants. Sloping the ceiling from the center usually works best.

Key Component #5: Mortars and Grouts

Because steam rooms are in a constant state of thermal flux, I recommend that only the most flexible mortars and grouts be used. For thin-set mortars this means ANSI A118.4 and ISO C2S2 for the cementitious bond coats. For grouts only those meeting ANSI A118.7 and ISO CG2 should be utilized. Maximum flexibility of the entire system is extremely important.

It is important for the design professional to ensure that the manufacturers of all key components are in full agreement with the intended use and interaction of their products prior to finalizing the specifications. If doubts or questions exist, procuring the help of an independent technically-qualified consultant should be considered. Steam rooms require intricate design. Even the smallest error can compromise the entire system and result in eventual long term failure.

(Editor’s note: Method SR614 will be up for a revision discussion in the June 2013 TCNA Handbook meeting in Atlanta.)


Tom D. Lynch is 50-year veteran of the ceramic tile industry with an installer, contractor and technical services background. Contact him at tommydlynch@gmail.com or on the Web at: tomlynchconsultant.com

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