failure, low mortar coverage is an obvious deficiency that implicates the installer, but the tile required a force to affect it. Would it have made a difference if better cov- erage as per ANSI A108 (≥80% interior; ≥95% wet and exterior) requirements were met? Maybe so, but all of the project conditions should be considered. Tiles with 100% mortar coverage have been found to loosen or crack under excessive structure/substrate move- ment conditions, but it’s much more difficult to prove that a con- crete slab or wood framing moved to an excessive degree. Two factors that greatly increase the probability of failure and reveal low mortar coverage are: • A non-absorptive/contaminated substrate • Inadequate frequency and size of movement joints (especially at all perimeters) This is because the forces listed above cause action (movement), and science shows that “for every action, there is an equal and oppo- site reaction.” If the mortar wasn’t bonded because of contaminants or lack of porosity, or the tiles have no space to move into, they fail much more easily regardless of mortar coverage. Insufficient mortar coverage makes projects susceptible to failure So is there any proof that indus- try-required mortar coverage makes a difference? In a word – yes! Thousands of projects have told the story that tiles with low mortar coverage are more suscep- tible to failure. The worst cases are spot-bonded tiles that fail when loads or thermal expansion cause movement. It doesn’t take much TECHNICAL FEATURE–––––––––––––––––––––––––––––––––––––––––––––––– Effects of ridge collapse based on technique and hammering on tile with mortar cured for 28 days TileLetter - mortar coverage article images and captions Correct method Swirled mortar Spot bonded leLetter - mortar coverage article images and captions Correct method Swirled mortar Spot bonded - mortar coverage article images and captions method Swirled mortar Spot bonded mortar coverage article images and captions ethod Swirled mortar Spot bonded TileLetter - mortar coverage article images and captions Correct method Swirled mortar Spot bonded TileLetter - mortar coverage article images and captions Correct method Swirled mortar Spot bonded Effects of ridge collapse based on technique and hammering on tile with mortar cured for 28 days Correct method Hammer good Swirl method Hammer bad Demo Spot bond 92 TileLetter | October 2018