Is Pooling Water on My Commercial Flat Roof Dangerous? The Honest Truth

If you own or manage a commercial building in Metro Detroit, you’ve likely looked up after a heavy rainstorm and seen puddles sitting on your flat roof. In the commercial roofing industry, there is a lot of confusion and misinformation about what is normal and what is a massive liability.

At Four Seasons Kanga Roof, we follow the principles of radical honesty. We want to give you direct answers so you can make informed decisions about your property. So, is pooling water on your commercial flat roof dangerous?

It can be. You have to determine if it is standing water or pooling water.

Standing Water vs. Pooling Water: What’s the Difference?

To understand if your roof is at risk, we need to look at the definitions provided by industry authorities like the National Roofing Contractors Association (NRCA).

• Standing water is defined by the National Roofing Contractors Association as (often referred to as short-term moisture) is any rainwater or condensation that naturally sits on a low-slope roof shortly after a rainstorm or heavy condensation event.
• It is considered normal for a flat roof to hold puddles for 12 to 36 hours while the water naturally drains or evaporates.
• Pooling or ponding water is defined as standing water that remains on a roof surface for 48 hours or longer during conditions conducive to drying.

The Danger and The Warranty Threat

If you have true ponding water, you have a serious problem. Major commercial materials from trusted brands like Elevate, Carlyle, CertainTeed, and GAF are designed to be incredibly durable, but they are not meant to be underwater indefinitely. Roofing Contractor Magazine and manufacturers agree on the risks.

• Because water can degrade roofing chemistry, weaken adhesives, and lead to structural sag, both manufacturers identify ponding water as a major hazard.
• If pooling is left unaddressed for long periods, it can potentially void specific roof warranties.

What Causes Pooling or Ponding Water?

We believe in transparency, which means holding the industry accountable. If your roof is pooling water, it wasn’t an act of nature—it was a design or execution failure.

• This is generally caused by the improper installation of the roof.
• The building code requires a ¼ inch per foot pitch to a flat roof.
• This encourages proper water flow.
• It could also be the improper placement or design of the drainage system on the roof.
• This can be the fault of the architect, builder, or roofing contractor.

Can You Fix or Prevent Ponding Water?

Yes. You don’t necessarily need a full roof replacement to fix a localized pooling issue.

• Normally it involves the removal of the area that the water is ponding at, and rebuilding the area to hold a minimum code pitch of ¼ inch per foot.
• This is achieved by using tapered insulation boards under the flat roofing membrane.

“Four Seasons Kanga Roof was completely transparent about our commercial roof repairs. They didn’t just try to sell us a new roof, they showed us exactly where the drainage was failing and fixed the root cause. Highly recommend their honest approach!” — Michael T. (Google Review)

If your Metro Detroit commercial property is struggling with ponding water, don’t wait for your warranty to void or your structure to sag. Reach out to Four Seasons Kanga Roof today, and let’s get your roof back to code.