Page 31 - Construction Waterproofing Handbook

WATERPROOFING PRINCIPLES—THE BUILDING ENVELOPE 1.13
recognize the importance of these termination and transition detailing, manufacturers must
provide the appropriate details with their specifications, and general contractors must provide
the coordination and oversight of the numerous subcontractors involved in a single envelope
for the completed product to perform as expected.
The 90%/1% principle is the reason that despite continuing technological advances,
waterproofing continues to be one of the major causes of legal claims in the design and con-
struction profession. It is not the actual manufactured waterproofing systems or envelope
components that leak but the field construction details involving terminations and transitions.

THE SECOND MOST IMPORTANT PRINCIPLE OF WATERPROOFING

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 attrib-
utable 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 fail-
ures include human installation errors, the wrong system being specified for in-place ser-
vice 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 in Chap. 2. More
often than not, the leakage would be attributable to improper application, including insuffi-
cient 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 typi-
cally involve actual and direct leakage and that the cause will have a 99 percent chance of
being anything but material failure.

PREVENTING WATER INFILTRATION

Considering that these two simple principles cover most leakage problems, it would
seem that preventing water infiltration problems would be easy. Certainly, prevention
of envelope failures must be a proactive process implemented before actual field