What are the requirements for installing a steam room in a residential or commercial application?
Installation guidelines are included in the TCNA Handbook.
Once you have picked out the materials for your installation, you should consult the manufacturer for their proprietary application procedures and warranties.
Why do I need a membrane for my steam room?
While glazed tile is vapor impermeable, the grout is not. In fact, cementitious grout easily transmits water and vapor. It is highly likely in a steam room assembly that vapor can pass through the grout. It may also be necessary to insulate the wall cavity due to differential temperatures on both sides of the wall possibly causing condensation. Each manufacturer may specify a different application of the membrane. Always check with the manufacturer's instructions.
Do I need a specific type of membrane for my steam room?
A waterproof membrane meeting the standards of ANSI A118.10 (as well as being rated and recommended by the manufacturer for the steam room application) should be used where ceramic tile is specified (bonded directly to the membrane or otherwise incorporated into the system). Always refer to the manufacturer's instructions and TCNA guidelines.
This is not at all the same as waterproof coatings used on building foundations or as might be used on wood decking. Rather, this is a specialty membrane which bonds to the substrate and to which tile can be bonded.
If using cement board, should the waterproof membrane go on top of or behind the board?
For thin-set applications (TCNA Handbook detail SR614), you will see that a waterproof membrane can be installed on top of, or behind, the cement board. However, some manufacturers require that the waterproof membrane be used on the front and a vapor membrane on the back. This tends to vary according to the manufacturer.
A surface application of the waterproof membrane has the advantage that the cement board fasteners do not puncture the membrane.
Can gypsum wallboard or "dry wall" be used in a steam room?
There are no details in the TCNA Handbook that incorporate gypsum wallboard in a steam room assembly. In general, the industry cautions against the use of gypsum wallboard in a steam room environment.
What kind of tile should be used in a steam room?
Virtually all tiles work well in steam room applications. However, as with all installations, it is worthwhile to discuss your intended use with a knowledgeable representative of the manufacturer.
Is drywall a suitable "solid backing" for methods B421 and B422?
B421 and B422 are shower methods in the TCNA Handbook in which a waterproof membrane is applied over an unspecified solid backing. The membrane must cover the solid backing under the entire area to be tiled. We are often asked if drywall is a suitable backing for these shower methods.
While some membrane manufacturers promote use of their membrane in such installations with drywall as the solid backing, other membrane manufacturers do not. At the same time, not all drywall manufacturers recommend their product be used in a shower, even if a membrane will be applied to the surface. Thus, the Handbook leaves the determination of a suitable membrane/backer board combination up to the membrane and backer board manufacturers to declare and up to the design professional to select/specify. Where materials manufacturers do not agree on a particular recommendation, a manufacturer is offering what's called a proprietary recommendation.
The International Building Code (IBC) is somewhat ambiguous on the topic. Many in the construction industry interpret it to say drywall is strictly prohibited in wet areas, regardless of whether a waterproof membrane would be applied to the surface of the drywall. Others feel the code only prohibits direct bond of tile to drywall in wet areas. Check with a local code official for your area requirements.
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