Water pooling on your flat roof can have adverse effects on your property. If you’re wondering how to address water drainage issues on your roof, it might be due to water retention. Finding a solution isn’t always straightforward. In this article, we will define the problem, explore potential causes, solutions, and the possible consequences if the issue is left unattended.
Ponding Water and Its Impact
The accumulation of water on a roof, known as ponding, can cause damage to your property. Ponding occurs when water remains on a roof for more than 48 hours. Large puddles can form due to an inadequate drainage system, issues with building infrastructure, or problems with roof design. Because of the volume of water, it can’t evaporate effectively from the roof’s surface.
After a storm, standing water might linger on a rooftop for up to three days. The National Roofing Contractors Association recommends having standing water on a roof inspected by a roofing contractor if it remains for more than 2 days.
Gravity is the force responsible for water pooling on flat roof. The only way for the water to be removed is through gravity-driven drainage. Over time, ponding water can pose a serious threat to the structural integrity of flat roofs, necessitating prompt attention.

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Workmanship vs. Quality of Roofing Materials
Martin J. Fradua from the University of Massachusetts points out that while most roof membranes aren’t completely waterproof, they do possess water resistance. This distinction is important when considering potential water-related damage. Although many flat roof membranes can repel water, their effectiveness is limited, especially in the face of substantial water accumulation.
Even the best roofing materials won’t prevent ponding water. To avoid water pooling on flat roof issues, it’s crucial to select an experienced roofer who can ensure proper installation. Simply purchasing high-quality membranes, flashing, and materials won’t eliminate the possibility of water pooling problems.
By choosing a reputable commercial roofer in your vicinity, you can save money by preventing unnecessary maintenance or repairs. Reach out for a complimentary quote on flat roof replacement.
Understanding Ponding Water: Causes & Solutions
Flat roofing installation by a contractor using rubber roofing rolls.
Mistakes in flat roofing installations are particularly common with rubber roofs. Here are some common causes of roof ponding:
1. Poor Roof Design: Many cases of water pooling are linked to poorly designed roofs. If architectural plans don’t align with the roof shape or building layout, roofing projects are destined for issues. Roofers inexperienced with flat roofs might not recognize potential problems from an external view. While flat roofs aren’t inherently difficult to replace or repair, consulting a structural engineer is advised if experienced roofers are financially unfeasible.
2. Age-Related Foundation Settlement: The passage of time inevitably leads to building foundation settling. Even well-intentioned designs can be altered by the shifting foundation. This sagging, most common in older structures but present in newer ones too, can affect the roof’s original design.
3. Rubber Roofs with Multiple Layers: Many urban areas, like Boston, have flat roofs with multiple layers. While rubber material is commonly used, it may not always be perfectly flat, which can exacerbate roof slopes.
4. Crushed Insulation and Uneven Roof Slope: Rubber roofing membranes typically have layers of insulation to regulate temperature. Proper insulation is crucial, especially in climates with extreme weather. However, insulation can be problematic due to its malleability. Snow accumulation or foot traffic can depress insulation, creating uneven surfaces perfect for ponding. Accumulated water in these depressions may not evaporate effectively.

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Solving Water Pooling on Flat Roof Issues
To address water ponding, adding insulation under the affected areas or adjusting insulation strategies can be effective. While this may be costlier, it prevents serious long-term issues caused by water accumulation.
Using Insulation Tape for Control
Tapered polyisocyanurate insulation, or tapered ISO, comes with built-in slopes. These slopes guide water toward roof drains, preventing ponding. Products like GAF’s EnergyGuard(tm) polyiso roof insulation tapered offer effective solutions for commercial roofing. Different slopes, such as 1% (1/8 inch per foot) and 2% (2.4 inches per foot), can be applied to roofs where polyiso is used.
Imagine a project using this insulation type to transform roof design, facilitating proper water flow toward gutters and drains.
Seek Expert Advice
If you’re considering roof replacement or repairs, consult a trusted roofing expert like Old Time Roofing. Contact local roofers for product pricing and guidance.
Are you tired of dealing with pesky water pooling issues on your flat roof? Look no further! Old Time Roofing is here to save the day. Our expert team specializes in addressing water pooling on flat roof problems that can lead to costly damage over time. With years of experience and a commitment to quality, we’ve got the skills to keep your roof in top shape. Contact us or visit our website to schedule your consultation. Let’s keep your roof strong and reliable, just like the good old times!
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Refrain from entrusting your roofing needs to just anyone. With Old Time Roofing, you can rest easy knowing that your roof is in capable hands. Contact us today!