Page 32 - Construction Waterproofing Handbook

1.14 CHAPTER ONE
construction activities commence. One of the first steps to implement this quality con-
trol process is to encourage preconstruction envelope meetings that include all subcon-
tractors involved in the building envelope and cover the following topics:

● Review of the building facade components
● Review of the proposed waterproofing and roofing systems related to the building
envelope
● Following the envelope barrier/drainage systems front line to ensure complete continuity
(covered in Chap. 11)
● Reviewing all transitions between envelope components to ensure effectiveness and
compatibility
● Reviewing all termination details for waterproofing adequateness
● Instructing all attendees on the necessity of meeting the 90%/1% and 99% principles
● Assigning the responsibility for each termination and transition detail
The last issue is often the root of the 90%/1% principle, the fact that many leaks are
directly attributable to transition details that are never installed because the general con-
tractor overlooks assigning responsibility for this details in their subcontracts. For exam-
ple, refer again to Fig. 1.9; whose responsibility would it be to install the reglet detail
provided for the below-grade waterproofing-to-dampproofing transition? The general con-
tractor might easily neglect assigning the completion of this detail to one of the involved
subcontractors.
Since the waterproofing membrane would be installed first in most cases, it would be
more appropriate for the dampproofing applicator to finish this detail. Although the masonry
contractor as part of their contract often applies dampproofing, few masonry contractors
understand the importance of this detail. What if the dampproofing used is a coal-tar-based
product that is incompatible with the urethane waterproofing membrane? Further compli-
cating the situation, an acrylic sealant might be used to finish the detail that is not compat-
ible with either the membrane or the dampproofing.
Such situations continually occur during field construction activities and result in facil-
itating the 90%/1% principle failures.
Unfortunately, all too often waterproofing is considered an isolated subcontracting
requirement, and few architects, engineers, general contractors, and subcontractors under-
stand the importance of knowing the requirements of successfully designing and con-
structing a watertight building envelope. It must be clearly recognized that all components
of a building exterior facade, from the backfill soil selected to the mechanical rooftop
equipment, are integral parts of the building envelope and that all are equally affected by
the 99%/1% and 99% principles.

BEYOND ENVELOPE WATERPROOFING

Besides preventing water infiltration, waterproofing systems prevent structural damage to
building components. In northern climates, watertightness prevents spalling of concrete,