Tags: #buildingscience #hygroscopic #materialsscience #roguetesting #waterresistance

Ponding tests: how this age-old technique offers new insights into the behavior of fluid coatings, coated glass facers, and integrated WRB panels. 

Our industry uses ponding tests to evaluate a wide range of phenomena, from water resistance of sheet membranes to sealant adhesion under water immersion. Last year, I wondered – what would happen if we combined one of the simplest, least stringent WRB testing methods with a 5-hour test duration typically reserved for 21.6-inch hydrostatic head testing? In other words, how low can we go to demonstrate what happens by sandwiching hydrophilic, hygroscopic materials together? Some things that made an impression…

  1. Glass-facers absorb water. Lots of water.
  2. Some fluid-applied AWBs also absorb water. Lots of water.
  3. Sandwiching hydrophilic, hygroscopic materials together allows capillary suction and vapor diffusion to do the things they do. The gypsum core is wetted.
  4. If allowed, the gypsum core will readily release its water. If not allowed, it will not.
  5. Repeated cycling of this process has its consequences.
  6. Gypsum-based integrated WRB panels are no better than conventional gypsum panels.
  7. And I was wrong about gypsum-based integrated WRB panels. It doesn’t take 7 inches, nor 21.6 inches, of water to wet their gypsum cores. It requires less than 3/16” and less than 5 hours.