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