Page 239 - Construction Waterproofing Handbook

4.14 CHAPTER FOUR
infiltration. In fact, the initial layer of felt installed prior to shingle installations can itself
provide water protection because of the ability of the roof to shed water so quickly.
New synthetic under-layments are being used in residential roofing systems. Figure 4.5
shows the proper application of the under-layments. Note how the edge is properly termi-
nated by turning the paper over the side onto the fascia board substrate. Figure 4.6 shows
under-layment installed with all seams sealed to provide added protection against water
infiltration.
As with other components of the house envelope, though, the leaks that do occur usu-
ally are associated with transitions, specifically at the plumbing stack penetrations and
flashings around such areas as chimney penetrations. Sealants usually are inadequate for
use in transitioning detailing under most circumstances, but they should be used to com-
pletely seal the transition use of flashings and caps on residential roofs.
This said, it should be recognized that flat roofs are not recommended for residential
construction. If an area is incorporated in the home’s exterior envelope, such as a balcony
or upper-level deck area, then the commercial systems described in Chap. 3 for horizontal
applications should be employed. These systems are provided with sufficient detailing by
the manufacturers for the homebuilder to properly install termination and transition detail-
ing to avoid water infiltration.

FIGURE 4.5 Proper application of roofing wrap with edges
properly sealed.