MIL-HDBK-1001/SA
water ponding, consider replacement in kind. Otherwise where adding slope is impractical, replace the membrane with a minimum of four plies in coal-tar pitch and aggregate surfacing. Also, consider providing additional drains where necessary. Asphalt, single-ply, or foam systems are not permitted on any roofs which will pond.
Where practical, a new roof design should incorporate positive slope that will eliminate all standing water conditions within a 24 hour period after rain. Review the number, type, sizing and location of drains, use of scuppers for overflow, and use of crickets for slope to prevent ponding between the drains. Never use wet fills to achieve slope.
10.4.2 The Insulation System. Consider the following:
a) Required R-value of the system;
b) Formation of roof slope including preformed tapered insulation;
c) Method of attachment to the substrate and new components to existing components and ability of existing construction to accept new attachments;
d) Compatibility with adjacent roof composite materials;
e) Fire and wind requirements;
f) Load carrying ability of the structure;
g) Dimensional stability relative to temperature change and exposure to moisture;
h) Product availability and maintainability;
i) Costs, life cycle economics, etc.
10.4.2.1 Tapered Insulation. Tapered insulation has the following disadvantages:
a) Difficult design coordination for flashing heights and other roof details affected by varying insulation thickness;
b) Require fairly complex field operations for some materials involving special drawings and coded insulation pieces;
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