Some domestic waste incinerators [1] have operated successfully with refractory tile systems for tube protection without using mortar to bond the tiles to the tube walls. Most tile protection systems installed around the world employ a paste of mortar behind the tiles to develop a rigid fixing system, with the presumption that the mortar provides another layer of tube protection behind the tiles. This paper examines the issues behind these approaches to tube wall protection and propose some guidelines for the use of refractories in these systems.