What is Ponding Water and Why Should I Fix It?

Roof systems are simply not designed to hold water. Even “flat” roofs contain a slight slope to maintain positive drainage. Ponding water is usually a sign of a drainage problem that needs to be addressed quickly to avoid bigger problems.

Ponding water on a roof can:

  • Act as a magnifying glass on the roof under the pond, which increases the damaging ultraviolet exposure of that area of the roof.
  • Contribute to the premature deterioration of the roof membrane, flashings and coatings.
  • Challenge the adhesives used to make field-fabricated single-ply laps, thus compromising the integrity of the roof system.
  • Attract insects, mold or vegetation
  • Collect dirt, which may cause the growth of vegetation or telegraph mud cracking to the roof below.
  • Cause structural damage to the building up to and including a roof collapse

As if all of that is not enough reason to address ponding water, it’s important to review the care and maintenance language of your roof warranty – many describe how a building owner is required to “maintain positive drainage,” or not allow water to pond and sit on a roof for 48 hours under dry conditions.

Maintaining positive drainage is a sound maintenance practice for any roof. If you see ponding water on your roof, don’t ignore it!

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