The inattention to detail is often exacerbated by overall poor workmanship that presents
the next most important principle of waterproofing:

The 99% principle: Approximately 99 percent of waterproofing leaks are attributable to causes other than material or system failures.

When considering the millions of square feet of waterproofing systems installed, both barrier and drainage systems, and miles of sealant involved in building envelopes, it can be estimated that only 1 percent of envelope failures and resulting leakage is actually attributable to materials or systems actually failing. The reasons typically involved in failures include human installation errors, the wrong system being specified for in-place service requirements (e.g., thermal movement encountered exceeds the material’s capability), the wrong or no primer being used, inadequate preparatory work, incompatible materials being transitioned together, and insufficient—or in certain cases such as sealants, too much—material being applied.

Today, with quality controls and testing being instituted at the manufacturing stage, it is very infrequent that actual material failures occur. For example, it is rare to have an outright material failure of a below-grade liquid-applied membrane, as presented later. More often than not, the leakage would be attributable to improper application, including insufficient mileage, improper substrate preparation, or applying over uncured concrete, among numerous other possible installation errors. Furthermore, it is likely that the leakage is also attributable to the 90%/1% principle, with inattention to proper detailing of terminations and transitions with the below-grade membrane occurring.

These two important principles of waterproofing work in unison to represent the overall majority of problems encountered in the waterproofing industry. By considering these two principles together, it can be expected that 1 percent of a building’s exterior area will typically involve actual and direct leakage and that the cause will have a 99 percent chance of being anything but material failure.

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