ANSI Who? 
Customers often ask me "Mike, I heard you mention ANSI. What the heck is an ANSI?"
Well, ANSI is an abbreviation for American National Standards Institute. What the fine people at ANSI do is pretty simple. They are a not-for-profit organization that compiles the standards that we in the tile industry use as a guide for the installation of tile and the materials that go along with it.
A committee made up of representatives from all over the tile industry called an Accredited Standards Committee or ASC, examines the many materials and methods of installation. Once they identify the materials and methods, the committee votes to either accept the method or reject the method. Once approved, the committee submits it to ANSI as a standard.
Many times, these standards are reviewed and improved upon.
Unlike other building trades, like plumbers and electricians for example, tile installers are not required a license to perform their work. The standards provided by ANSI allow tile installers to function from a base set of guidelines. For example, ANSI A108.5 (Installation of Ceramic Tile with Dry-set Portland Cement Mortar or Latex-Portland Cement Mortar) describes how to mix the mortar(s), how to apply the mortar and what materials can be used with the mortar(s). It also provides details that describe the installation of specific materials in specific fashions, like 2.4 Setting ceramic mosaic tile. These standards eliminate the guess work. They also help to provide a uniform approach to how tile and stone is installed.
While there are many professionals in the industry that adhere to the standards, be wary of those installers who are not familliar with them. Ignoring the best practices or standards will lead to certain eventual failure.
For your own copy of American National Standard Specifications for the Installation of Ceramic Tile, visit The Tile Council of North America (TCNA) website at the following link: http://www.tileusa.com/