Page 443 - Construction Waterproofing Handbook

THE BUILDING ENVELOPE: PUTTING IT ALL TOGETHER 10.45
incorporate these trades and systems into an envelope are candidates for errors and result-
ing water infiltration. This multiple-discipline requirement highlights the importance of
requiring a preconstruction meeting that involves all parties who affect roof performance
and resulting envelope watertightness.
This conference must include electricians, mechanical contractors, and curtain wall and
waterproofing subcontractors, in addition to any of those people listed above who are
included in specific project requirements. Each contractor must be made aware of his or
her responsibility to interact with all other trades for successful completion of an envelope.
Terminations and transition details are reviewed, and require the manufacturer’s preap-
proval of all project details. This review should include discussion and resolution of the
following frequent causes of envelope infiltration related to roofing:

● Inadequate and improper transition and termination details
● Inadequate drainage (no flat roofs), and absence of testing for proper slopes before
installation
● Too many separate roof penetrations
● Too much equipment and traffic on roof areas
Manufacturers should be consulted by designers to review proposed detailing, to ensure
that the system will adequately function under the proposed job-site conditions. Any
unusual conditions expected to be encountered, such as equipment penetration and traffic
on roof, should be carefully reviewed to ensure a material’s adequacy.
During project bidding stage, manufacturers should preapprove proposed installers and
allow only those contractors who are familiar with the procedure and trained to compete
for the roof installation contract. This coordination should continue through the actual
installation, with reviews and inspections conducted as necessary by the manufacturer.
Finally, by requiring joint manufacturer and contractor warranties, the manufacturer con-
tinues its involvement throughout the warranty period. Warranties are discussed in detail
in Chap. 11.

1/90 PERCENT PRINCIPLE

Throughout this book, emphasis is given to proper selection and installation of envelope
waterproofing systems. As this chapter has shown, however, successful installation goes
beyond selection and application of a single envelope component. Only if all individual
components of a building’s envelope have adequate transitions with one another will a
building remain watertight and weather-tight.
This is especially true of buildings that use a variety of composite finishes for exterior
surfacing such as brick, precast, or curtain wall systems. These designs incorporate a vari-
ety of waterproofing methods. Although they might each act independently, as a whole
they must act cohesively to prevent water from entering a structure. Sealants, wall flash-
ings, weeps, dampproofing, wall coatings, deck coatings, and the natural weather-tightness
of architectural finishes themselves must act together to prevent water intrusion.
As many as 90 percent of all water intrusion problems occur within 1 percent of
the total building exterior surface area.