MIL-HDBK-1001-5 Roofing And Waterproofing S/S By Mil-Std-3007This handbook sets forth guidelines for design of roofing, LAYOUT 1 and waterproofing systems for building construction. It covers design of new low-slope and steep roof systems, reroofing of existing buildings, and waterproofing, and dampproofing systems.

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MIL-HDBK-1001/SA

Section 9: STEEP ROOFING

9.1       Steep Roofing Description.  Steep roofing comprises a wide variety of roofing materials used on slopes exceeding 1-1/2 inches per foot (14 percent).  Shingles, shakes, and tiles depend on the gravitational-force component provided by slope to assure positive water-shedding.  The gravitational water shedding force must exceed all the opposing forces (kinetic, capillary, and atmospheric suction) tending to draw water up the slope between overlapping roof units.  A slope of 4 inches per foot (33

percent) is adequate for most steep roofing systems to assure dependable water-shedding.  When used on lower slopes (less than

1-1/2 inches per foot (14 percent)), steep roofing requires additional measures to assure good performance.

9.2       Materials.  Steep roofing materials including the following:  asphalt shingles, asphalt roll roofing, wood shingles and shakes, clay and concrete tiles, metal, and slate.  Consult the NRCA Steep Roofing Manual, the SMACNA Architectural Sheet Metal Manual, and the Asphalt Roofing Manufacturers Association (ARMA) Residential Asphalt Roofing Manual for steep roofing details.

9.3       General Design Requirements

9.3.1     Slopes.  Minimum slopes for various steep roofing materials are shown in Table 2.  In snow country, designers should consider hazards of sliding and drifting snow.

9.3.2     Decks.  Structural plywood decks facilitate the most convenient, economical, and dependable fastening techniques. Other deck materials, such as concrete, require installation of nailing strips, laths, horizontal battens, etc.  These are described in the NRCA Steep Roofing Manual.

9.4       Underlayments.  Several purposes are served by underlayments:

a)  To keep the deck dry until shingles or tiles are installed;

b)  To provide secondary water resistance protection if shingles or tiles are damaged, wind-lifted, or if wind-driven

rain or water behind ice dams at cold eaves ever penetrate beyond the overlapped shingle;

c)  Form a cushion for slates;

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