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-1001/5A

percolation course, well-drained insulation, and smooth-finished surface.

b)  Locate roof drains where they will not freeze.  The first few feet of pipe from drains must be thermally protected in cold regions.  Provide weep holes in drain at each sub-assembly level.

c)  Consider using elevated scuppers in case drains become blocked.

d)  In geographical areas subject to intense rainfall, overflow drains should be considered.  Overflow drains are smaller in diameter than regular drains.  They are placed upstream 10 to 15 feet (3048 to 6096 millimeters) and terminate

at the top of the insulation, or percolation course, if included, with weep holes at the membrane level.  The drain cage must be fine enough to prevent infiltration by percolation materials.

8.3.2        Percolation Course.  The optional percolation course is designed to allow easy and free access of water to the drains and the insulation above to dry.  This rock course should be graded

1-1/2- to 2-inch (38- to 51-millimeter) maximum size.  It must be rescreened before sending to the roof as fines develop in

transit.

8.3.3     Flashings.  Flashings for a PMR are essentially the same as for conventional roofs.  They are, however, more vulnerable to damage, especially at cants adjacent to pavers. They should be carried a minimum of 8 inches (203 millimeters) above the roof's surface.

8.4       Variations.  The insulation may be placed directly on the membrane, and the percolation course can be placed directly

on the insulation with its filter fabric.  The percolation course then serves as a ballasted finish.

8.5       Other Considerations

8.5.1     Single-ply or Liquid Membrane.  A four-ply fiberglass built-up system set in hot bitumen or a modified bitumen system are the most common membranes used in a PMR.  However, a single- ply or liquid membrane may also be used.

8.5.2     Expansion Joint.  In flush joints, never drape membrane materials in or over an expansion joint.  Use preformed joint formers.

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