One of the most important components to a properly functioning flat roofing system is proper and adequate drainage.

Roof slope allows gravity to draw water off of a roof, thus promoting drainage. Without adequate slope, a roof could heavily pond water causing significant damage to a roof system, or in extreme conditions, even building collapse. The roofing industry, National Roofing Contractors Association (NRCA) and U.S. Ply have adopted the recommendation that all low-slope roof structure be constructed with positive slope with a minimum recommendation of ¼" per foot (1.2°) slope on new construction and 1/8" per foot (0.6°) slope on existing structures.

It should also be noted that ponding water areas are excluded in U.S. Ply roofing system guarantees. The reason for the exclusion is that ponding water can cause significant adverse effects on a roof system, including:

• Adding weight, thus increased deck deflection, possibly increasing "creep" of structural members and further increasing weight, deflection and ponding. In extreme cases, the increased weight can cause the roof structure to collapse.
• Increased surface protection loss such as coatings or granules further intensifying UV damage from inadequate protection.
• Intensifying UV damage by magnifying sunlight, thus accelerating deterioration of the roof membrane, especially asphalt based products.
• Splitting from ice formations undergoing freeze/thaw cycles
• Increased accumulation of residual dirt, thus increasing potential for organic growth. The plants die and hollow roots act as conduits to admit water.
• Increased opportunity for extended system damage from leakage.

Many drainage problems on flat roofing systems can be avoided by using tapered roof insulation. Sumped roof drains can also offer improved drainage. For questions about your roof drainage, more tips, and additional information on this topic, contact U.S. Ply and let us help you. Call us Toll Free at (877) 628-7759 or email at info@usply.com.