Here is some great info from North American Tile to help understand the different systems and applications
Owner - 360renos.ca
The Old Fashioned Way, Long Before Wallboard Panels ....
|Mud Wall (Started):|
Wall mortar beds could be built plumb to fix ANY imperfections or uneveness on a vertical surface.
|Mud Wall (Finished):|
Skilled and experienced tradepeople were required for this kind of work
|But now we have backerboard, and as the construction industry evolved other products were developed to create similar results in less time. Cement Board ultimately replaced the old way of doing things. Cement Board Units (CBU) were installed over top the studs with either a vapor barrier behind the cement board panel, or a moisture proof membrane was applied over top the cement board. This became the industry standard for ceramic tile or stone installation in wet or moist areas.|
After awhile, other products came on the market that made the installation of backer board even easier. GreenBoard was one of them. Basically it is a glorified gypsum board which was never able to resist moisture as it claimed. Garbage in ANY wet area of application. DenShield was also a gypsum product which seemed to have a high succcess rate IF installed as recommended by the manufacturer.
Moisture has always been the greatest concern and the determining factor for failure or success of any ceramic tile installation in showers, saunas, tub surrounds etc. WEDI Board is waterproof, light-weight and super easy to install. Basically, the choices are many but it's important to understand which product to use for each installation requirement.
Most backerboards are an acceptable addition to floor installations, but never assume they stiffen or strengthen a floor. They are a good base for bonding and may act as an uncoupling membrane ... BUT they will not reduce deflection. That can only be accomplished with plywood, solid blocking, added support under the floor or additional (larger) joists.
Each ceramic tile or stone installation is unique as are the methods and materials used to create every individual sysytem. So before you start loading up the shopping cart .... find the correct solution for your project.
Remember to ensure all your studs are plumb and flat before installing the backerboard. Unlike the old fashioned mortar walls which could be applied plumb and flat ... backerboards will follow the contours created by your existing studs or other surfaces.
Backer Board for Floors
|Cement Board for Floor Application ... WRONG!||This photo was sent in by Brian (forum moderator) and clearly shows the WRONG WAY to install ANY floor panel. In this case there are combined factors headed for failure. The cement board isn't set into a bed of mortar, and there is an underlayment (1/4" mahogany) which isn't meant to be part of a ceramic or stone tile system.|
|Most backerboards used for floor applications must be set into a thin bed of thinset mortar. This application of mortar is meant to fill in voids that usually exist between various layers thus removing the possibility of deflection. Screws or other recommended fasteners are still required for a mechanical bond.||Visit the links below for each manufacturer's recommendations.|
The following product descriptions are quoted in part from each manufacturer's website.
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