erly placed joints consistent with EJ-171 from the TCNA Handbook or the manufacturer’s recommen- dations. Another common failure is excess water of convenience. This is water introduced from the initial process of mixing the dry-set mor- tar that is not used or absorbed in the process of hydration, but becomes trapped between an impervious layer of tile and a moisture-resistant substrate water- proofed or treated to keep water OUT. Now that combination is working to keep water IN. This is a prevalent explanation for freeze-thaw failures. There may be excess water in your installation even though you have assured the perimeters have proper flash- ing intended to keep new water out. Add lack of coverage and/ or improperly troweled substrates and now you have ready-made cavities for nature to exploit. This is all made possible because often the least-trained person on the crew is the one mixing and delivering the mortar to the better- trained installer who wanted a “looser mix” that did not kick off too fast. The request to “just add a little more water” because they were working outside in the heat or direct sun becomes the first of a series of dominoes that combine to create a future failure waiting to occur. That is an easy scenario to imagine. It is also an innocent set of circumstances created by even the most well-meaning crew. This is just one more reason to seek out and use qualified labor. It’s practi- cally guaranteed that the installer offering the “best” (cheapest) price is the one in this scenario that is the least aware and will be paying the least attention to the seem- ingly innocent error of overwater- ing the mortar. Corrective repairs take at least triple the time necessary to install it right the first time. Exterior repairs are undoubtedly more complicated. They seem to be required at the most challeng- ing, least accessible place on the project. Gone is the luxury of an unoccupied workspace. Traffic control and public safety require difficult coordination, which add costs and risk. Add the costs of the need for specialized labor and possibly additional equipment, you now have a blend of compli- cated requirements to be avoided at all costs. In the meantime, let it rain… Chris Walker NTCA President Vice President, David Allen Company Chairman, ANSI A-108 Chairman, US TAG ISO TC-189 Board of Directors ABC-VA Voting Member TCNA Handbook Voting Member NTCA Reference Manual chriswalker@davidallen.com PRESIDENT'S LETTER ––––––––––––––––––––––––––––––––––––––––––––––––– 22 TileLetter | June 2019