FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

11 Designing the builDing envelope Volume II
until such coefcients have been developed. A consensus test method for uplift resistance has not been
developed for wood shingles or shakes.
For enhanced durability, preservative-treated wood is recommended for shingle or shake roofs on coastal
buildings. Stainless steel fasteners are recommended for roofs within 3,000 feet of an ocean shoreline
(including sounds and back bays). See Figure 11-54 for an example of shingle loss due to corrosion of the nails.
Figure 11-54.
Loss of wood shingles
due to fastener corrosion.
Hurricane Bertha (North
Carolina, 1996)
11.5.7.2 Hail
At press time, no wood-shingle assembly had passed UL 2218, but heavy shakes had passed Class 4 (the class
with the greatest impact resistance) and medium shakes had passed Class 3.
Te hail resistance of wood shingles and shakes depends partly on their condition when afected by hail.
Resistance is likely to decline with roof age.
11.5.8 Low-Slope Roof Systems
Roof coverings on low-slope roofs need to be waterproof membranes rather than the water-shedding coverings
that are used on steep-slope roofs. Although most of the low-slope membranes can be used on dead-level
substrates, it is always preferable (and required by the IBC and IRC) to install them on substrates that
have some slope (e.g., 1/4 inch in 12 inches [2 percent]). Te most commonly used coverings on low-slope
roofs are built-up, modifed bitumen, and single-ply systems. Liquid-applied membranes (see Section 11.5.3),
structural metal panels (see Section 11.5.5), and sprayed polyurethane foam may also be used on low-slope
roofs. Information on low-slope roof systems is available in Te NRCA Roofng Manual (NRCA 2011).
Low-slope roofng makes up a very small percentage of the residential roofng market. However, when lowslope
systems are used on residences, the principles that apply to commercial roofng also apply to residential
11-48 COASTAL CONSTRUCTION MANUAL