Consequences of Ponding Water on Your Commercial Roof

  Ponding water is a significant issue for commercial flat roofs. While flat roofs are not entirely flat—designed with slight slopes for drainage—water can still accumulate in low-lying areas after heavy rains, creating small pools or "ponds." If the water remains for longer than 48 hours, it can result in what is known as ponding. While it might seem like a minor inconvenience, ponding water can lead to a range of serious problems that may compromise the integrity of your roof and building.

As professional roofing contractors in Detroit, Michigan, Motor City Roofers has seen firsthand the damage that ponding water can cause. In this article, we'll explore the potential consequences of ponding water on your commercial roof and discuss how you can prevent and address this common roofing issue.

1. Structural Damage to the Roof
One of the most significant risks of ponding water is structural damage to your roof. Water is heavy, and when it collects on your roof, it can put extra stress on the building’s structure. Over time, this additional weight can cause the roof to sag or even collapse in extreme cases. A single square foot of water that’s an inch deep weighs about 5 pounds. When water accumulates over a large area of the roof, the extra weight can become substantial.  If your roof already has minor structural weaknesses or damage, ponding water exacerbates these issues, accelerating the deterioration of the roof deck or membrane. Over time, this can lead to costly repairs or the need for a full roof replacement.

2. Increased Risk of Leaks and Water Intrusion
Ponding water increases the likelihood of leaks in your commercial roof. The water can seep into small cracks or gaps in the roofing material, eventually making its way into the underlying structure. Prolonged exposure to standing water can wear down the roof’s protective membrane, causing it to weaken and allowing moisture to penetrate. Once water infiltrates your roof, it can lead to internal water damage, including mold growth, rotting insulation, and compromised ceilings or walls.  Leaks can be particularly damaging for commercial buildings, as they may interrupt daily operations and result in significant repair costs. In some cases, tenants or businesses inside the building may need to vacate the premises temporarily while repairs are made, leading to further disruptions and lost revenue.

3. Accelerated Deterioration of Roofing Materials
​Many roofing materials are designed to be weather-resistant, but they are not meant to handle continuous exposure to standing water. Ponding water can accelerate the degradation of roofing materials like EPDM (ethylene propylene diene terpolymer), TPO (thermoplastic polyolefin), and modified bitumen. Over time, the constant moisture can break down these materials, causing them to crack, blister, or separate at the seams.
The sun’s ultraviolet (UV) rays also play a role in the deterioration of roofing materials. When water sits on the roof, it amplifies the effects of UV radiation, much like a magnifying glass. This increases the rate at which the roofing material breaks down, shortening the lifespan of the roof and potentially requiring expensive repairs or a premature replacement.

4. Growth of Mold, Algae, and Vegetation
Standing water on your commercial roof provides an ideal environment for mold, algae, and even vegetation to thrive. Mold and algae growth can be particularly harmful to roofing materials, as they can break down the protective layers and cause the roof to deteriorate more quickly. In addition to causing structural issues, mold can also affect the indoor air quality of your building, potentially leading to health problems for employees or tenants.  In some cases, vegetation may begin to grow in the ponding water, especially if dirt or debris has accumulated on the roof. Plant roots can penetrate the roof membrane, causing further damage and creating new pathways for water to enter the building. Once plants take root, they can be difficult to remove and may require costly repairs to restore the roof to its original condition.

5. Impact on Energy EfficiencyPonding water can negatively affect the energy efficiency of your commercial building. Many modern commercial roofs are designed with reflective coatings or membranes that help reduce heat absorption and keep the building cool. However, when water pools on the roof, it reduces the effectiveness of these reflective surfaces, allowing more heat to be absorbed by the roof and transferred into the building.  This can lead to increased energy costs, as your HVAC system will need to work harder to maintain a comfortable temperature inside the building. In addition to higher utility bills, a less energy-efficient building can also result in a larger carbon footprint, which is increasingly a concern for environmentally conscious businesses.

6. Voiding of Roofing Warranties
Many roofing manufacturers offer warranties that cover defects in materials or workmanship. However, most warranties have specific conditions that must be met to remain valid. One of these conditions often includes proper drainage and maintenance of the roof. If ponding water is not addressed promptly, it can void your roofing warranty, leaving you responsible for the full cost of repairs or replacement.  Failing to maintain your roof properly can also lead to insurance issues. If water damage occurs due to ponding and it’s determined that the issue was preventable, your insurance company may deny the claim, forcing you to cover the repair costs out of pocket.

7. Ice Damming in Cold Weather
In regions like Detroit, Michigan, where cold winters are common, ponding water can lead to ice dams on your commercial roof. When temperatures drop, the standing water can freeze, creating ice dams that block proper drainage. These ice dams can further damage the roofing material and increase the risk of leaks. As the ice expands and contracts, it can cause cracks in the roof membrane or even tear the material, leading to costly repairs.  Additionally, the weight of the ice can be even more damaging than the weight of standing water, as ice is heavier and more rigid, putting additional stress on the roof’s structure.

Preventing Ponding Water
The best way to avoid the consequences of ponding water on your commercial roof is through regular maintenance and proactive repairs. Here are a few tips to prevent ponding water:

1. Regular Inspections: Schedule regular roof inspections, especially after heavy rainstorms. Look for areas where water tends to pool and address any issues promptly.
2. Ensure Proper Drainage: Make sure your roof has adequate drainage systems in place, such as gutters, downspouts, and internal drains. Clear debris from these systems to ensure proper water flow.
3. Roof Slope and Design: If ponding water is a recurring issue, you may need to adjust the slope of your roof or install additional drainage solutions.
4. Roof Maintenance: Regularly clean and maintain your roof to prevent the buildup of debris that can block drains or cause water to pool.

Ponding water on your commercial roof can lead to a host of problems, including structural damage, leaks, material degradation, mold growth, and energy inefficiency. By addressing ponding water issues early and ensuring proper roof maintenance, you can extend the life of your commercial roof and avoid costly repairs. If you’re dealing with ponding water on your roof, contact Motor City Roofers in Detroit, Michigan, for a professional inspection and tailored solutions to protect your building.