Identifying the Number of Plies

Rolls come in standard and metric sizes: 

Standard- 36"         Metric 39 3/8"

2-ply standard:   17-inch ply exposure

2-ply metric:       18 9/16-inch ply exposure

3-ply standard:   11 1/4-inch ply exposure

3-ply metric:       12 7/16-inch ply exposure

4-ply standard:     8 1/2-inch ply exposure

4-ply metric:          9 5/16-inch ply exposure

 

INSPECTION CONCERNS

Design and Installation Deficiencies

• Improper repairs;
• Failed or improper flashing;
• Bubbles/blisters;
• Cant strip at parapets. Built-up membranes should not turn upward 90 degrees. Corners should be softened by installation of cant strips.
• Proper terminations at penetrations, walls, and roof edge;
• Adequate slope/positive drainage/signs of ponding;
• Craze-cracking (alligatoring: jargon, this term not used in narratives);
• Inadequate drain method;
• Inadequate flood coat thickness;
• Flood coat creep;
• Membrane creep (inadequate attachment to deck);
• Less than 8" elevation above the surface (curbs, penetrations, etc). Common with re-covers;
• Inadequate number of expansion joints;
• Expansion joints impede drainage

 

Weathering and Maintenance Issues

• Flood coat weathered away (mat/reinforcement visible);
• Base flashing exposed reinforcement;
• Embrittlement and cracking;
• Splitting due to wetting of organic reinforcement (typically happens due to rapid temperature drop);
• Drain blockage;
• Disloved asphalt from AC condensate; and
• Disolved asphalt from greases/oils.

 

Wind, Hail and Mechanical Damage

• Hail damage (spatter or impact damage including collateral damage);
• Wind-caused ballast scouring near perimeter and corners;
• Wind-dislodged cap flashing;
• Wind uplift damage; and
• Damage from wind-borne missiles