FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

11 Designing the builDing envelope Volume II
Figure 11-29.
Underlayment that was
not lapped over the hip;
water entry possible
at the sheathing joint
(arrow). Estimated
wind speed: 130 mph.
Hurricane Katrina
(Mississippi, 2005)
Shingle Products, Enhancement Details, and Application
Shingles are available with either fberglass or organic reinforcement. Fiberglass-reinforced shingles are
commonly specifed because they have greater fre resistance. Fiberglass-reinforced styrene-butadiene-styrene
(SBS)-modifed bitumen shingles are another option. Because of the fexibility imparted by the SBS polymers,
if a tab on a modifed bitumen shingle lifts, it is less likely to tear or blow of compared to traditional asphalt
shingles. 13 Guidance on product selection is provided in Fact Sheet 7.3, Asphalt Shingle Roofng for High-
Wind Regions, in FEMA P-499.
Te shingle product standards referenced in Fact Sheet 7.3 specify a minimum fastener (nail) pull-through
resistance. However, if the basic wind speed is greater than 115 mph, 14 the Fact Sheet 7.3 recommends
minimum pull-through values as a function of wind speed. If a fastener pull-through resistance is desired
that is greater than the minimum value given in the product standards, the desired value needs to be specifed.
ASTM D7158 addresses wind resistance of asphalt shingles. 15 ASTM D7158 has three classes: Class D, G,
and H. Select shingles that have a class rating equal to or greater than the basic wind speed prescribed in
the building code. Table 11-1 gives the allowable basic wind speed for each class, based on ASCE 7-05 and
ASCE 7-10.
Shingle blow-of is commonly initiated at eaves (see Figure 11-30) and rakes (see Figure 11-31). Blow-of of
ridge and hip shingles, as shown in Figure 11-29, is also common. For another example of blow-of of ridge
13 Tab lifting is undesirable. However, lifting may occur for a variety of reasons. If lifting occurs, a product that is not likely to be torn or
blown off is preferable to a product that is more susceptible to tearing and blowing off.
14 The 115-mph basic wind speed is based on ASCE 7-10, Risk Category II buildings. If ASCE 7-05, or an earlier version is used, the
equivalent wind speed trigger is 90 mph.
15 Fact Sheet 7.3 in FEMA P-499 references Underwriters Laboratories (UL) 2390. ASTM D7158 supersedes UL 2390.
11-30 COASTAL CONSTRUCTION MANUAL