What type of adhesive should I use?

There are a couple different types of adhesive on the market today and I will help to separate the two.With both , there are what they call regular use and then also a multi purpose use. The multi purpose has better bonding qualities, and can be used in wet areas such as shower walls and such.

Mastic is a pre made glue that comes in tubs. Thin set is a cementous sand and cement blend that comes in large bags and needs to be made by mixing water and stirring with a drill and a paddle spoon. I think the primary difference is ease of usage and spanning over less than smooth substrates. All tile or marble installations benefit best from having a smooth , flat substrate to begin with. I like to tell people it needs to be "paint able" to give you the best finished product. With that said, mastic is a great choice if your tile installation is the kind that you can smear some glue and then press the tile into the glue tight to the wall and move on. Smaller wall tiles work well in this fashion, such as 4x4's, subway tile, mosaic sheets ect. Unless unusually heavy, once placed in place the mastic will hold the piece in place so that it will not slide down the wall.

Larger tile create a bit of a challenge simply put, because there less forgiving when the span a larger distance and usually need a bit of help to make them lie flat to each other so a good thinset , mixed to proper thickness will help to fill voids behind the tile and will also allow you to press the corners of the tiles to massage them flatter next to each other. If need be you can also pull the tile and add a dollop behind it in low places to shim the edge out to help make it flush with surrounding pieces. This process is done repeatedly on floors if the concrete is not truly flat. That by the way, is normally the case on concrete. Never use mastic on concrete. And if you choose to use mastic for installing natural stone make sure it's specifically designed for such use.

Cost is the last factor. Mastic is more expensive but often times it's grabbing capabilities, its longer open time on the wall, and easability of use will, in the long run be money well spent.

Ryan Carlson
Custom Touch Interiors
http://www.customtouchinteriors.com/