I recently read an article about which board to use when installing shower tiles. I wanted to share with you. It was written by Cory Laws, not myself.
As a contractor, I've repaired lots of showers or tub/shower combinations where leaks have caused walls to fail. In these high moisture areas, there's a simple cause of the rotting walls, and a correspondingly simple solution. The first step is to use the appropriate materials.
The problem with these areas is the frequent direct exposure to water. The space between tiles is filled with grout, which is a porous mortar like substance. Treated with a sealer, there is good water resistance, but this must be done periodically for maximum protection. If not, seepage occurs, which even without cracks that often develop, can compromise the grout and allow more and more infiltration, till the supporting wall collapses. Additionally, because houses flex, corner seams usually crack. Here, "grout caulking is a good idea. Because caulking is flexible too, using it on all seams will keep the seam water tight. Regular caulking works, but grout caulking will match the color of the grout, and give a very nice and consistent appearance.
The "moisture resistant" drywall, identified by its green color (commonly called Green Board), is designed for use primarily in "limited wet areas". A favorite of builders, it's widely used in bathrooms, and as the "tile backer" for tub and shower areas. Unfortunately, Green Board is far from the best product for this application. Once it gets wet, it deteriorates relatively quickly. Additionally, it has no mold resistance, an issue many homeowners are becoming more aware of. There are other products that offer not only superior strength in damp or wet areas, but also provide protection against mold.
DUROCK® Cement Board DUROCK Cement Board is a very durable base for premium finishes including glass and ceramic mosaics, ceramic and quarry tile, and thin stone and brick. The mold- and moisture-resistant board does not deteriorate in the presence of water so it is extremely durable in areas such as baths and showers. DUROCK Brand Cement Board is backed by a 30-year warranty for interior applications.
Hardie Board Hardie Board is another moisture and mold resistant substitute for drywall, similar to DUROCK and a good backerboard for your tile applications. Although no system is mold proof, HardieBacker™ board with its Moldblock™ Technology delivers very high mold resistance, passing both industry mold tests with a perfect score.
DensShield Tile Backer A relatively new product on the market, DensShield is one of a family of products featuring "Design Moisture Forgiveness", a pairing of energy efficiency and moisture resistance required by new "tighter" building practices.
The above products will dramatically reduce the potential for problems with your tiled walls. However, coupled with a product like RedGuard, any issues will likely be prevented. RedGuard is a waterproof membrane that is "painted" over the tile backer board. I usually use it in showers, especially custom showers with tile over cement floors. I've yet to experience any problems.
The article resides at http://www.novapros.com/blog