FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

Volume II DESIGNING THE BUILDING 9
EXAMPLE 9.1. ROOF SHEATHING NAIL SPACING FOR WIND UPLIFT (continued)
Solution for #1: The following calculations are used to determine the nail spacing:
• From Table 8-8, the maximum wind suction pressure (based on ASD design) is:
where:
p = 108.7 psf acting normal to the roof surface (Zone 3 overhang) for Exposure Category C
The maximum wind suction pressure for Exposure D is:
p = 108.7 psf (1.18)=128.3 psf
1.18 = the adjustment factor from Exposure C to Exposure D at 33-ft mean roof height (see
Example 8.10)
• The assumed minimum tributary area for calculation of this pressure is 10 ft 2 in accordance
with Example 8.7
• For framing at 16 in. o.c., roof suction loads in plf are:
• Nail spacing:
Rounding down to next typical spacing value, specify 4-in. spacing
Solution for #2: The following calculations are used to determine the nail spacing:
• From Table 8-8, the maximum wind suction pressure is:
p = 108.7 psf acting normal to the roof surface (Zone 3 overhang) for Exposure Category C
See Figure 8-18 and Table 8-8.
The maximum wind suction pressure for Exposure D is:
where:
p = 108.7 psf (1.18)=128.3 psf
1.18 = adjustment factor from Exposure C to Exposure D at 33-ft mean roof height
(see Example 8.10).
• The assumed minimum tributary area for calculation of this pressure is 10 ft 2 in accordance
with Example 8.7.
COASTAL CONSTRUCTION MANUAL
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