answered 7/6/2008 We Are Tiling The Bathtub Using Greenboard Around The Tub, With Sheetrock For The Other Portion Of The Bathroom. Can We Adhere Ceramic Tile On Sheetrock Portions That Extend The Area Of Greenboard? And Can We Use Mastic? You can apply tile to Sheetrock only in small quantities such as backsplashes or borders around tubs and showers. Entire shower walls should be applied to a concrete type backer board.