June 2019 President's Letter
Tuesday, September 17, 2019
Posted by: Trish Moss
Let it rain, snow, freeze, thaw...
Mother Nature is very unforgiving. She will almost certainly exploit any error or omission incorporated into an exterior installation. Doing it right is always important; for exterior installations, it’s critically important. Floors or walls: both will be unforgiving if the materials are poorly installed.
The June TileLetter might seem to be a strange place to talk about the risks of installations exposed to freeze-thaw. But while it’s 70-80 degrees outside and you are preplanning your exposed installations, it is the perfect time to be aware of how to protect yourself from the unintended result of performing exterior installations without the utmost care and planning. This is the time to verify you have used the correct products from the top of the tile to the bottom of the assembly. Poorly- and/or improperly-executed installations can begin to fail within the first freeze-thaw cycle. Never was the advice of a knowledgeable allied products representative more important than to affirm that the correct products were specified and are ideal for an exterior installation. Then hypersensitivity to the manufacturer’s recommended use and preparation instructions are required.
Think about the installations you have noticed that have “gone wrong.” Latex leaching, efflorescence, tenting, unbonded materials… you get the picture. All of those are examples of what happens when you don’t do something right with what you put in and what you leave out.
In fact, it might be true that what you LEAVE OUT is the most important piece of the installation. You figured it out already: expansion and contraction joints. It is difficult to fathom just how much relative movement there is in an exterior installation exposed to sunlight. Think of a dark surface in the sunlight and how a drop of rain can take the material from 120 degrees to 70 degrees in seconds. Now that is thermal shock! If you want your installation to have a fighting chance, you need to allow it to deal with those extremes. You need to truly understand the necessity of properly placed joints consistent with EJ-171 from the TCNA Handbook or the manufacturer’s recommendations.
Another common failure is excess water of convenience. This is water introduced from the initial process of mixing the dry-set mortar 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 waterproofed 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 flashing 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 practically 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 seemingly innocent error of over-watering 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 challenging, 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 complicated requirements to be avoided at all costs.
In the meantime, let it rain…
Vice President, David Allen Company
Chairman - ANSI A-108
ChairmanUS TAG ISO T-189
Board of Directors ABC-VA
Voting Member TCNA Handbook
Voting Member NTCA Reference Manual