The conclusion is that cement board is the only product you should be using when there is any chance of contact with water. Many times it's what you don't see behind the walls that has the biggest impact for longevity of your project.
For a tile backing material in wet areas such as showers or tub alcoves, cement board (combined with a moisture barrier) or glass mat panels are far better choices. Sag and outright failure often occur when the greenboard has been subjected to wet conditions over time.
Walls: Use 1/2-inch or 5/8-inch-thick cement board, not 1/4-inch. The extra thickness is needed when spanning the studs and it provides a solid base for the tile. Countertops: 1/4-inch, 1/2-inch, or 5/8-inch-thick panels are all suitable for countertops.
Tile installation using GoBoard® by Johns Manville saves you time in all your projects, including mudrooms, bathrooms, entryways or showers. GoBoard® is an ultra-lightweight, waterproof, and durable tile backer board that is easy to cut and install.
GoBoard itself is waterproof. To ensure a waterproof tile assembly, all fastener locations and joints (between boards, corners and other changes of plane) must be sealed completely with GoBoard Pro Sealant or a waterproof sealant (see www.JM.com/GoBoard for approved alternative sealants).
What type of thinset can be used on GoBoard? You can use modified or non-modified thinset on GoBoard installation projects.
Cement boards, like Durock and WonderBoard, are water-resistant…but they are not waterproof. When you are using cement backer boards in a shower or around a bathtub, or really anywhere that is going to get wet, you need to think about waterproofing.
If it's a cement board, you need a vapor barrier, because cement retains moisture, which means the wood next to it is always damp.
Cement Board and a Liquid Membrane
In this application, cement board is installed directly onto the studs. No plastic sheeting goes behind the cement board. A liquid waterproofing membrane, such as RedGard or Hydro Ban, is rolled onto the cement board and allowed to cure. Then, tile is installed over the membrane.
Hardiebacker is significantly lighter than Durock and WonderBoard, leaving this the lightest out of the bunch. How light it instantly makes it one of the most popular brands on the market. Since there isn't any glass mesh in it, unlike Durock, it makes the job much smoother and even minimizes the cleanup.
Purple drywall is both mold and moisture resistant, and is another great choice to use in bathrooms, but it's much more forgiving than green board when it comes into contact with water. You can use purple drywall for the ceiling and/or upper walls of a shower, for example.
The purpose of a cement backer is to create a surface for you to tile onto. The surface is straight and flush; taking away the worry of an uneven wall or floor. As it is cement, it is resistant to mould, rotting and moisture damage meaning it is the perfect backer for showers, kitchens and bathrooms.
Traditionally, ceramic tiles have been the material of choice for waterproofing shower walls and cubicles, but these days, shower panels are an increasingly popular choice for these areas in our homes. This is because they offer all of the waterproofing and aesthetic properties of tiles, but without the disadvantages.
Many professional installers even recommend against using water- or mold-resistant drywall in high-moisture areas. In sharp contrast, cement backer board does not rot, warp, grow mold, or deteriorate when subjected to water. Cement backer board is mainly used as a sub-surface for tiling.
Generally, liquid waterproof membranes can be applied by home owners for a basic, quick, and economical means to waterproof your shower. If you are looking for a much more robust and longer-term service, going with some sheet membrane or foam backer board is most likely your best bet.
Cement boards may be classified as water resistant as they are not affected by water exposure; however, they do allow penetration and passage of water and water vapor. To waterproof cement boards, a liquid or membrane waterproofing material is applied over its surface.
For most interior applications, Durock® Brand Cement Board Panels are not affected by water and do not need to be waterproofed. Durock® is water durable but not waterproof. If you're looking for added protection to water sensitive material behind the Durock®, you may consider adding a waterproofing membrane.
Doing this will require that you remove the existing surface material before installing backer board over the studs. Cement board can also be used on countertops when laying tile. However, the process will involve using an extra sheet of backer board. Never use standard screws when installing cement board.
Is a vapor barrier required for wet area wall applications? GoBoard does not require a vapor barrier for wall applications unless required by local building codes or when installed in steam shower applications.
GoBoard Washers can be used in all GoBoard tile backer board applications for maximum holding strength. Take advantage of increased allowable spacing when used in combination with GoBoard Fasteners, or fortify your installation for heavier or larger format tile.