Why Roof Ponding Leads to a Sea of Troubles

Whether your commercial roof is single-ply, built-up or modified bitumen, roof ponding can cause great damage in short order. Ponding may be the source of your own building’s flat roof leak. Identifying and repairing ponding problems can help prevent permanent damage. 

What is Ponding

Water that remains on your building’s flat roof more than 48 hours after precipitation is called ponding. Your so-called “flat roof” should have a minimum pitch of 0.25 inches per linear foot to help water drain, but this is ideal, and roof decks do have unique dips and low spots. Any one low spot or deformation in the deck can lead to a flat roof leak. 

Causes of Ponding

Besides an incorrectly pitched roof or deck deformations, other sources of ponding can lead to a flat roof leak:

  • Clogged internal drains or parapet scuppers
  • External units that stop water—HVAC or other rooftop units that stand in the downward path of water will collect that water at their bases, leading to ponding. A professional roofer can install crickets to divert flowing water around the units. 
  • Crushed insulation below the roof surface—This is a key reason to keep foot traffic off your commercial property’s roof; the boots crush insulation

Results of Ponding

Once started, ponding tends to increase, since the water weight deforms the deck further. Each new rain brings larger pond formations. Additional issues: 

  • Algae and plant growth take hold, relying on the ponds for water
  • Wind deposits organic matter, dirt and trash in the depressed areas, scouring the roof surface
  • Standing water has plenty of time to soak into rooftop insulation, between modified bitumen layers, or into the deck itself

Ponding Prevention

A commercial property owner can prevent most ponding and the subsequent damage. After any heavy rain, one person (to minimize foot traffic) should survey the roof and sweep water out of low areas. Ensure scuppers and drains are free-flowing. Other smart moves to prevent a flat roof leak: 

  • Lift, do not sweep, larger debris from the roof
  • Remove all organic material with every rooftop visit
  • For long-term corrections, get a professional roofing contractor to add tapered insulation and the right membrane, such as PVC roofing, that resists standing water

Beldon Roofing is ready and able to provide sensible, effective solutions to pondingContact Beldon Roofing today to learn more about PVC membranes, tapered insulation and our preventive maintenance. 

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