What Causes Ponding or Puddles of Water on a Flat Roof?

If you’ve noticed ponding or puddles of water forming on your flat roof after a rainstorm, you’re probably wondering, “Do I have a problem with the ponding or puddles of water on my flat roof?” The short answer is yes—especially if your puddles of water stay for long periods of time.

At Rocky Mountain Roofing Services, we’ve been providing roof services to protect homeowners, commercial properties, and building managers from water damage due to ponding water for over 35 years in Albuquerque and Santa Fe. We know how a small puddle can quickly lead to a major roof ponding water problem.

Let’s examine the reasons why water collects on flat roofs, what happens to a flat roof if ponding water sits too long, and what roof repairs can be made.

Should Water Collect on a Flat Roof?

Although flat roofs are designed to have a slight slope in order to allow for drainage, water collecting on a flat roof for any length of time after an event (storm) raises an immediate red flag. If you have a puddle of water on your flat roof for more than 48 hours after a storm stops, you will need to investigate your roof drainage system (drains, scuppers, gutters).

If a drainage system fails to perform effectively, water can begin to gather and cause damage to your roof by deteriorating the roofing system and creating a roof leak.

How Can Ponding Water Cause Damage?

Ponding – or standing water – can lead to significant damage to your roof, including:

• Deterioration of Your Roofing System. Commercial roofing systems can typically withstand a great deal of weight; however, a rooftop with constant or extended ponding will deteriorate your roofing system significantly quicker (regardless of whether your roof is made of TPO, EPDM, or modified bitumen). Moisture kills adhesives and weakens seams and softens the insulation beneath the roofing system.
• Costly Leaks. Standing water will weaken the roofing materials creating a leak. Even a small hole or loose seam will let water inside your building. Leaks can go unnoticed until serious damage has occurred.
• Excessive Weight on Your Roof. Most building owners are surprised at just how much weight a flat rooftop carries. One inch of standing water on a ten-foot by ten-foot area weighs over 500 pounds. Multiply that by the size of your roof, and you will find that you have hundreds, possibly thousands of pounds of weight added to your flat roof. Most flat roofs are not designed to carry that weight long-term. Excessive weight will cause your roof to sag and create low spots, where more ponding will occur. It can ultimately cause your entire structure to be structurally unsound.
• Growth of Algae, Mold, and Vegetation. Standing water on flat roofs tends to attract dirt and debris just like a small pond; therefore, standing water on flat roofs provides the perfect setting for algae, mold and vegetation development. This will break down your roofing membrane and clog the drain system. Mold growth in your building can also create health problems for your employees or tenants.
• Loss of Your Warranty. The warranty on most commercial roofing systems contains very specific clauses regarding the drainage system. If your manufacturer determines that the damage to your roof was the result of standing water, they may not cover the costs of roof repair.

How Long Can You Leave Ponding Water on a Flat Roof?

If standing water remains for 48 hours after a storm ends, it is defined as ponding water. Once it becomes ponding water, it should be addressed immediately. The presence of standing water, known as ponding, often leads to huge roof issues if not dealt with immediately.

How to Fix or Eliminate Ponding Water on a Flat Roof

How do I fix or eliminate ponding water on a flat roof? This is a very common question we receive, and the following is a list of proven solutions to help reduce or eliminate the problem:

1. Clean and maintain your roof drains. Clogged drains create the majority of standing water problems. Clean your roof drains of any debris (leaves, trash, etc.) regularly and ensure that your scuppers and gutters are free from clogs.
2. Inspect the roof for low spots. Settled or compressed areas of insulation can create low areas on the roof; therefore, ponding occurs. You can correct this by using tapered insulation or additional materials to create a slope.
3. Inspect your roof for improper slope or design. All flat roofs must have at least a slight slope (¼ inch per foot) toward the drains or edges. If the slope of your roof has changed for some reason, then water will not flow off your roof, resulting in ponding water.
4. Add or upgrade roof drains. In most instances, the best way to eliminate or reduce ponding water is to install additional roof drains or scuppers. Adding additional roof drains or scuppers to problem areas helps pull water away from those areas; large additions to a building or heavier equipment can cause your existing drains or scuppers to be inadequate for your building’s current requirements.
5. Regular roofing inspections. Regular inspection of your roofing system can uncover issues before they become major issues. Rocky Mountain Roofing Services offers detailed inspections regularly as part of its Roof Maintenance program, which can help identify these issues early-on and correct them in a cost-effective manner.

Should You Sweat Puddles of Water on Your Flat Roof?

If you have questions about standing water on your roof, including “Are puddles of water a problem on my flat roof?” and “How do I reduce or eliminate standing water from damaging my flat roof?” you are asking the right questions.

The good news is that most problems with standing water can be resolved by taking the appropriate action early on. Smaller puddles of standing water can lead to very large restoration costs if left unattended to.

Final Thoughts Concerning Flat Roof Water Ponding Issues

Rocky Mountain Roofing Services works with property owners, both residential and commercial, to help correct ponding issues and extend the life expectancy of their roofs. If you are currently experiencing problems with ponding water or just want peace of mind concerning the condition of your roofing, we are committed to providing our clients with smart, cost-effective roofing choices.

Let’s make sure those puddles of water on your flat roof do not develop into major roof repair problems. You may reach out by completing our Get Quote form or at any time via phone: 505-717-1925. We are always happy to provide our customers with additional information or assistance concerning their roofing needs.