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



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