Metro Atlanta doesn't do gentle rain. When a summer storm rolls through Cobb or Gwinnett County, it tends to arrive fast and heavy, and then move on just as quickly. For businesses with flat or low-slope roofs, that pattern is exactly the kind of stress test that exposes drainage problems most other roof types never have to deal with.
A flat roof isn't actually flat. It's built with a slight, deliberate slope designed to move rainwater toward drains, scuppers, or gutters. When that system works the way it should, you'd never notice it. When it doesn't, standing water becomes a recurring, expensive problem.
What Counts as a Drainage Problem, Not Just a Puddle
Some standing water after a heavy storm is normal and not cause for concern. The commonly used industry benchmark is that water remaining on a low-slope roof beyond about 48 hours after rain, under conditions conducive to drying, points to an underlying drainage issue rather than ordinary runoff. If the same puddles reappear after every storm, or take days to dry instead of hours, that's your building telling you something needs attention.
It's also worth paying attention to where the water collects. Puddles that consistently form in the same spot, especially near a rooftop unit, curb, or drain, point to a specific, fixable cause. Water that seems to spread across a wider area or shift location after different storms can be harder to diagnose without a professional look at the roof's slope and structure.
Common Causes of Flat Roof Ponding in Georgia
- Clogged or slow drains and scuppers. Georgia's tree cover and pollen season are notorious for filling roof drains with debris faster than many building owners expect.
- Structural deflection. Over time, the roof deck can sag slightly under its own weight or added rooftop equipment, creating low spots where water naturally collects.
- Compressed insulation. Foot traffic and heavy rooftop equipment can compress insulation beneath the membrane, forming shallow depressions that trap water.
- Poor slope around penetrations. HVAC units, curbs, vents, and skylights interrupt water flow, and if the surrounding area wasn't sloped correctly during installation, water pools around these features.
- Undersized or poorly placed drainage for the roof's size. Larger commercial roofs sometimes need additional drains or specialized systems to move water fast enough during Georgia's heavier storm events.
Why Ponding Water Is a Bigger Problem Than It Looks
Standing water is more than a cosmetic issue. It adds significant weight to the roof deck, and that added weight can cause further deflection, which in turn creates more ponding, a cycle that gets worse over time if left unaddressed. Ponding water also accelerates membrane wear, contributes to leaks at seams and penetrations, and can void portions of a manufacturer's warranty if left unresolved.
The National Roofing Contractors Association's guidance on roof slope and drainage design outlines how proper slope, tapered insulation, and correctly placed drains are meant to work together to prevent this exact scenario.
How Drainage Problems Are Usually Fixed
- Clearing and servicing existing drains and scuppers, which resolves a surprising number of ponding complaints on its own.
- Installing tapered insulation systems to correct low spots and restore proper slope toward existing drains.
- Adding crickets or saddles around rooftop equipment and curbs to redirect water around obstacles instead of letting it collect against them.
- Adding supplemental drains or scuppers on larger roofs where the existing drainage system simply isn't enough to keep up with heavy Georgia storms.
Prevention Beats Repair, Especially Before Storm Season
The most cost-effective way to deal with flat roof drainage is to never let it become a real problem in the first place. Georgia's pollen season each spring is one of the biggest, and most preventable, contributors to clogged drains on commercial roofs across the metro area. A quick seasonal drain-clearing before the heavy spring and summer storms roll in can prevent months of standing water and the deck stress that comes with it.
Routine visual inspections are just as important. Because ponding tends to develop gradually, catching a new low spot early, before it deepens or spreads, is far easier and less disruptive than waiting until water is visibly failing to drain after every storm. Building this kind of check into a seasonal maintenance routine is one of the simplest ways Georgia businesses protect their roof investment.
Don't Wait for the Next Downpour
If you've noticed standing water that doesn't drain within a day or two after a storm, it's worth having it looked at before it becomes a leak, a warranty issue, or a structural concern. Our commercial roofing services team can assess what's actually causing the ponding on your building and walk you through what it would take to fix it properly, rather than just patching around it.
Frequently Asked Questions
How long is too long for standing water on a flat commercial roof?
A common industry guideline is that water remaining on the roof for more than about 48 hours after rain, under conditions conducive to drying, indicates a drainage problem rather than normal runoff.
Can ponding water actually damage my roof, or is it just cosmetic?
Ponding water adds weight to the roof deck, accelerates membrane wear, and can lead to leaks or structural deflection over time. It can also affect manufacturer warranty coverage if left unaddressed.
Do I need a full roof replacement to fix a drainage problem?
Not usually. Many drainage issues are resolved with drain cleaning, tapered insulation adjustments, or added crickets around rooftop equipment, all of which are far less invasive than a full replacement.
🏆 Voted Best Roofing Company — My Woodstock/Canton Area Best of 2026
Tom & Jerry's Roofing is proud to have won the Best Roofing Award in the My Woodstock/Canton Area Best of 2026 awards, a reflection of our commitment to quality craftsmanship and honest service throughout Woodstock, Canton, and the greater Atlanta metro area. Thank you to our community for the trust and support — we're honored to keep serving you with roofs (and service) built to last.