I want to install ceramic tile on a kitchen backsplash. There is currently drywall where I want to install the tile, between the countertop and cabinets. Can I install directly to the drywall or do I need to remove it and install a concrete board?
When selecting installation methods and materials, how the area will be used in service must be considered. The TCNA Handbook for Ceramic, Glass and Stone Tile Installation has a section called Environmental Exposure Classification that deals with this issue. There are both Residential and Commercial ratings, which mainly deal with the amount of moisture an installation will receive. A kitchen backsplash like you described would most likely fall into Residential 1 classification (Residential dry). If the surface will not be exposed to moisture or liquids except for cleaning, there are recognized and acceptable methods for installation over gypsum board like methods W243 and W242, found in the Handbook. These methods describe the details for approved installations over gypsum board.