14 2018 | TECH able. The installation itself will, over time, relay its sound- ness and reliability. In other words, when tile or grout issues do appear, the tile contractor should be consulted first and any govern- ing workmanship requirements for the project should be scrutinized in order to distinguish installation concerns that don’t meet them from those that do. An inspection may be in order if working with the contractor doesn’t remedy issues, or to explore if other conditions outside the tile contractor’s control are also factors. Bias in assessments When seeking an installation assessment, whether a formal (paid) inspection or a more informal opinion – such as by a manufacturer’s or distributor’s product representative – be aware of the various forms of bias that cause faulty opinions or conclusions. For example, even where spot bonding or poor mortar coverage has been identified, such may be only a contributing factor to tiles debonding. A curing compound that inhibits bonding may have been topically applied to a concrete substrate but not disclosed to the tile contractor. Or perhaps a substrate deflects (bends) beyond what even properly installed tile would endure, caused by overloading or under-designing a floor for anticipated weight/loads. The installer’s work should not be char- acterized as wholly to blame when there are other contributing factors. This is no defense for spot bonding or poor workman- ship, but rather a caution about fast, easy conclusions. Too often tile contractors are the only target when things go wrong, perhaps because the installer’s work is easily observable and photographed, comparatively inexpen- sive to evaluate, and fairly basic to comprehend: a handy smoking gun. A more thorough assessment (e.g., struc- tural evaluations, laboratory testing of concrete, etc.) will be significantly more expensive, more difficult to arrange because of the scarcity of people who can conduct a specialized study, and the results are often more complex even though more accurate. Generally, such exhaustive research will not be under- taken over some broken or missing tiles, let alone just a hollow sound. In the field of statistics, terms like missing data bias and omitted-variable bias refer to the inaccu- racy of a conclusion resulting from leaving out relevant variables or information. Specifically, conclusions will overestimate the effect of the variables and information that were included. There’s also confirmation bias, which makes it difficult for people to interpret information objectively, particular- ly when something significant is at stake. It’s a cognitive phenomenon that makes it equally challenging for the tile contractor, product rep, building designer, etc., to believe negative information about their work or product. To avoid faulty conclusions about tile installations when complete research will not be commissioned, TECHNICAL FEATURE (continued) Precast hollow-core concrete offers performance and logistical advantages over poured-in-place concrete, but an installation substrate or component with intentional voids can contribute to hollow-sounding floors. Computer software can help determine mortar coverage that has been achieved using a photograph. This tile was calculated to have about 60% coverage.