MIL-HDBK-1001/SA
Section 6: SINGLE-PLY ROOFING SYSTEMS
6.1 Single-Ply Roofing Description. A membrane, sheet or liquid-applied, with only a single layer of material designed to resist water penetration.
6.1.1 Single-Ply Sheet-Applied Materials. Sheet-applied membranes can be chemically classified in one of the following categories: elastomers (synthetic rubber), plasticized thermoplastic polymers, uncured elastomers, or modified bitumens. (Refer to Table 1 for membrane adaptability to different roof systems.)
6.1.1.1 Elastomeric Sheet. The most common elastomeric sheet is ethylene propylene diene monomer (EPDM).
Field lap seams are the most vulnerable component in elastomeric sheet systems. EPDM is a thermosetting polymer and requires use of contact adhesive and tape. Contact adhesive generally requires:
a) thorough cleaning of the material with solvent- soaked rags;
b) a waiting period for the contact adhesive to attain proper consistency;
c) thorough pressure-sealing of the lap; and
d) application of a side lap sealant for temporary protection while the contact adhesive cures.
Defective seams are vulnerable to rainwater ponding, especially frozen water. Prolonged water intrusion impairs the performance of neoprene-based contact adhesives. Non-neoprene- based adhesives are significantly less vulnerable to moisture intrusion.
6.1.1.2 Plasticized Thermoplastic Sheets. Plasticized thermoplastic sheets are represented by PVC membrane sheets, reinforced and unreinforced. Watertight field lap seams are formed in PVC sheet by comparatively easily installed solvent- welded or heat-welded lap seams. These seams are true fusions of base and jointing material.
A major liability of PVC sheet membranes is that they may, under certain exposures, become embrittled and shrink from
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