travertine tile bathroom

Q. I have a 2nd floor shower with moisture resistant sheetrock. I want to put 18" travertine tile on the walls above the pan. Using modified mortar, can these tiles be put on the wall with mortar blobs leaving an air space behind tile or do the tiles need to be buttered completely and stuck on walls leaving no air space between tile and sheetrock?

A. First, moisture resistant sheet rock is not the appropriate type of backing material. It will not hold up. I would suggest you tear out the sheet rock and replace it with a cement type backerboard such as Durorock or WonderBoard. The tile should be set in a full mortar bed. The spotting method is not the appropriate setting method.

Fred Hueston
Chief Technical Director, SurpHaces
President, Stone Forensics