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

Section 5: BITUMINOUS BUILT-UP ROOF MEMBRANE

5.1       Material Description.  As the weatherproofing component of a built-up roof system, the built-up bituminous membrane comprises three elements: bitumen, felts, and surfacing.

5.1.1     Bitumen.  Bitumen resists water penetration in the interply adhesive films mopped between felt layers and the bituminous surface-coating or flood coat.  The two types of bitumens are blown (i.e. oxidized) asphalts and coal tar pitch.

5.1.2     Felts.  Felts stabilize and reinforce the membrane. Felts prevent excessive bitumen flow when the bitumen is warm and semi-fluid and distribute contractive tensile stress when the bitumen is cold and glasslike.  Felt plies separate the interply bitumen moppings and provide the membrane's multiple lines of waterproofing defense.

5.1.3     Surfacing.  Surfacing of built-up membranes comprises one of four basic types: aggregate, smooth, mineral surfacing, or protective/reflective coating.

5.1.4     Flashing.  Flashings seal the joints where the membrane is interrupted or terminated.  Base flashings, essentially a continuation of the membrane, form the edges of a watertight "tray."  Counterflashings shield or seal the exposed joints and edges of base flashings.

5.1.4.1   Base Flashings.  Recommended materials are the following:

a)  One ply of granular surfaced modified bitumen sheet, over 2 plies of glass-fiber felt.

b)  Three-ply glass-fiber felt (sometimes reinforced and granular surfaced).

c)  Metal base flashings should be restricted insofar

as practicable to vent-pipe seals, gravel-stop flanges, and drain

flashings, where there are no practicable alternatives.

5.1.4.2   Counterflashings.  Counterflashings (sometimes called "cap flashings") are usually made of metal:  aluminum, galvanized steel, stainless steel, copper, or lead sheets designed to shield exposed base flashing joints and shed water from vertical or slanting surfaces onto the roof.

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