Fixing Ponding Water on Modified Bitumen Roofs

By Travis Haessly, The Roof Champion of Columbus

Ponding water is one of the most common problems we see on flat roofs, especially with modified bitumen systems. If you're a homeowner in Columbus or the surrounding suburbs and your roof holds standing water for more than 48 hours after rain, it's not something to ignore.

Let's walk through what causes it, what it means for your roof's lifespan, and how we fix it.

What Is Ponding Water?

Ponding water is any water that doesn’t fully drain from your roof within 48 hours after precipitation ends. It usually shows up on low-slope or flat roof areas.

Modified bitumen roofing systems, while tough and durable, are still vulnerable if water collects in the same areas over time. The big risks include:

• Membrane degradation

• Blistering

• UV damage

• Premature failure of seams

• Mold growth or structural damage below the deck

Why Does It Happen?

Here’s what usually causes ponding:

• Improper slope or deck deflection

• Poor drainage design or clogged drains

• Degraded insulation (especially with wet or compressed layers)

• Shifting substrate due to settling or poor installation

The NRCA and ARMA both recommend roof deck deflection not exceed 1/240 of the span under load—but many older roofs in Columbus and surrounding areas weren’t built to today’s codes.

How We Fix It

At The Roof Champion of Columbus, our approach always starts with inspection and diagnosis. Here are the solutions we recommend based on what we find:

1. Tapered Insulation Systems

This is our go-to method for correcting slope. We install rigid polyisocyanurate foam board insulation in sloped layers to redirect water to drains.

• Code-compliant

• Adds thermal value

• Compatible with modified bitumen

• Eliminates large ponding areas permanently

2. Crickets Behind Roof Protrusions

If water collects behind HVAC units, skylights, or chimneys, we custom-fabricate crickets to divert water around the obstruction. These are installed under the membrane during repairs or reroofing.

3. Adding or Unclogging Drains

Flat roofs without proper drainage just won’t perform. Sometimes all it takes is cleaning out debris. In other cases, we’ll retrofit new internal drains or scuppers to ensure fast water removal.

4. Structural Repairs

If the deck is sagging or has deflected due to water damage or aging, we may need to rebuild the substrate. This is especially important for wood or gypsum decks, where hidden damage can worsen over time.

5. Localized Leveling with Repair Ply

On smaller problem spots, we can use self-leveling compound or additional base plies to reduce low areas—usually as a temporary measure or part of a larger repair.

What Not to Do

Here’s what we never recommend:

• Don’t coat over ponding areas without fixing the slope. Most coatings are not rated for ponding water and will fail.

• Don’t patch over saturated insulation. Wet layers must be removed and replaced.

• Don’t ignore the problem. The longer you wait, the more it costs to fix later.

Real Talk from Travis

We helped a homeowner in Worthington last year who had a commercial-style modified bitumen roof on their addition. For years, they ignored ponding—until a leak came straight through the kitchen ceiling. We installed tapered insulation with a cricket system and added a new scupper. Not a drop since. That’s how we do things: we don’t quit until it’s right.

FAQs

How do I know if ponding is damaging my roof?
Look for signs like alligatoring, blistering, or granule loss around the ponding areas. If the water’s always in the same spot, call us for an inspection.

Can a roof coating fix ponding issues?
No. Most coatings (especially on asphalt systems) are not rated for standing water and will fail unless slope is corrected first.

Is ponding covered by insurance?
Typically not unless it leads to covered damage like collapse or interior leaks. Prevention is key.

Call the Roof Champion

If you’re in Powell, Westerville, Dublin, Gahanna—or anywhere in the greater Columbus area—and you’re seeing standing water on your flat roof, don’t wait. We’ll give you an honest assessment and walk you through your options.

📍 The Roof Champion of Columbus
177 Chasely Circle, Powell, OH 43065
📞 (614) 639-3422
🌐 www.roofchampcolumbus.com