The Residential Building Code can be a little tricky when it comes to where gypsum products can and cannot be used within a home. Contractors as well as homeowners are often faced with a variety of interior wall products which are available through both wholesale and retail stores.
To determine what gypsum product can be used at a particular location, you must first take into account conditions such as; water exposure, humidity, vapor retarders and possible tile application. It is not uncommon to find tile used in bathroom and shower locations; but what interior wall products are approved and suitable for these areas of the home, can cause confusion.
The Residential Building Code (R702.4.2) list specific types of backer-board materials which may be used as a tile substrate at tub and shower locations. Generally, these products are either cement based or contain some type of fiber mat in lieu of standard gypsum materials.
What about the green or blue gypsum board products? These products seems to cause the most confusion when it comes to approved locations, as well as allowable tile applications. The green and blue products are considered “water-resistive”, which the code addresses in R702.3.8. In this section you will find that the code does not allow for these products to be installed over a class 1 or 2 vapor retarder (R702.7) in shower and tub compartments.
Note, the reference above specifically addresses shower and tub compartments. It is ok to install water resistive gypsum at other locations, such as areas around bathroom and kitchen sinks. Because of the requirements listed above, it is not uncommon to find as many as three different types of interior products used on today’s homes.
For more information on this subject go the Gypsum Association and click on wall tile.
For more information on vapor retarders go to North American Insulation Manufacturers Association.
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