MIL-HDBK-1001/SA
Section 2: STRUCTURAL DECK
2.1 Functions. The structural deck serves two functions:
a) For structural resistance to gravity, wind and seismic forces;
b) As substrate for the roof system.
2.2 Design Factors. Structural decks must be designed with consideration of the following design factors:
a) Slope for drainage;
b) Dimensional stability;
c) Moisture absorption;
d) Anchorage (for wind-uplift resistance);
e) Deck surface and joints;
f) Expansion joints.
2.2.1 Drainage. In new construction, provide slope for drainage in the structural deck, when practicable, with minimum slope of 1/2 inch per foot (4 percent). For reroofing, provide a minimum slope for drainage of 1/4 inch per foot (2 percent). (Refer to Section 10.) Provide saddles or crickets in valleys
and other locations requiring additional drainage-promoting techniques. Locate drains at low points, i.e., at center of simple spans and other locations of maximum vertical deflection.
Where provision of slope in the structural deck is impracticable specify tapered (sloped) insulation to provide slope. The choice between interior or exterior drains depends upon building size and configuration and local climate. Provide interior drains in cold climates where subfreezing temperatures may create drain-blocking ice in exterior drains.
Design the primary drainage system to accommodate the rainfalls listed in DM-3.01, Plumbing Systems. Where the roof is bounded with perimeter parapets, design a scupper system as secondary drainage, with bottom scupper elevations designed to limit ponding depth to a structurally safe depth in case the primary drains are clogged. Design perimeter scupper drains by
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