News flash: poor mortar cover- age doesn’t “cause” a tile fail- ure! If you’ve ever replaced an old tile installation that seemed per- fect, you’ll agree. It took a hammer and chisel to reveal that 20-year old “poor” mortar coverage. The reality is that it always takes a force or condition of some kind to exert stress somewhere in the tile assem- bly to loosen or crack a tile. So what are these other forces? What are the best methods to over- come them? How do they relate to coverage? In regards to coverage, what does experience tell us works best to achieve it? Causes of tile failure The primary forces that cause tile failures are: • Structural movement including shrinkage and creep (sagging over a period of time) • Substrate deformation such as deflection, vibration or curvature from load • Environmental conditions includ- ing thermal growth and freeze/ thaw stress • Impact – single or repeated When subjected to these forces, the tile assembly will either accom- modate or resist displacement, or fail. Tile and stone are fairly rigid and have a tight limitation for movement, making installation design a major factor for success. Will the structure/substrate provide stability for the assembly? Was the assembly chosen with the building usage in mind? In a forensic examination of a TECHNICAL FEATURE ––––––––––––––––– A realistic look at mortar coverage Poor mortar coverage may not cause a tile failure, but it’s an important factor in tile installation success By Mike Micalizzi, Sr. Director of Technical Services, Custom Building Products Superior ilt remium otch Trowels m E amples of brea age and delaminatio Superior ilt remium otch Trowels ma e ridges are easier to collapse fo Examples of breakage and delami- nation as a result of poor mortar coverage 90 TileLetter | October 2018