FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

11 Designing the builDing envelope Volume II
Figure 11-24.
Small area of sheathing
that was exposed
after loss of a few
shingles and some
underlayment. Estimated
wind speed: 140 to 160
mph. Hurricane Charley
(Florida, 2004)
Figure 11-25.
Typical underlayment
attachment;
underlayment blow-off is
common if the shingles
are blown off, as shown.
Estimated wind speed:
115 mph. Hurricane
Katrina (Louisiana, 2005)
secondary protection requires an enhanced underlayment design. Design enhancements include increased
blow-of resistance of the underlayment, increased resistance to water infltration (primarily at penetrations),
and increased resistance to extended weather exposure.
If shingles are blown of, the underlayment may be exposed for only 1 or 2 weeks before a new roof covering
is installed, but many roofs damaged by hurricanes are not repaired for several weeks. If a hurricane strikes
a heavily populated area, roof covering damage is typically extensive. Because of the heavy workload, large
numbers of roofs may not be repaired for several months. It is not uncommon for some roofs to be left for as
long as a year before they are reroofed.
11-26 COASTAL CONSTRUCTION MANUAL