While they are a staple of the commercial world, flat roofs are becoming more popular on residential structures. You may have purchased a home with a flat roof or added one to your garage or home addition. While flat roofs can be beautiful and modern, many homeowners are unprepared for how different these systems are from sloped roof systems.
For example, flat roofs may develop a problem called ponding that doesn’t occur on sloped roofs. Ponding is when water collects in puddles on the roof instead of draining off in a timely manner. Homeowners may think this small amount of water is harmless, but ponding tends to get worse over time and can have a negative impact on the roof and your whole home.
If you own a flat roof, it is essential to understand what counts as ponding, why it happens, and how to resolve it before it damages your roof and home. We’ll explain the basics of ponding and why it’s a wise idea to get a professional involved as soon as possible when your flat roof has ponding.
Roof ponding is where water gathers on a flat roof. So how much ponding is acceptable on a flat roof? Specifically, water must remain on the roof for 24-48 hours for the National Roofing Contractor’s Association (NRCA) to consider it ponding. If you have this leftover water, you may notice it collects in dips in the roof or around drains.
Even minor ponding can have a serious impact on your roof and your home. The excess weight from the water may cause damage to the building’s structure, especially if it exceeds the safe weight that the home can carry. Even if it does not, increased weight can stress the roof trusses and other parts of the building.
Constant exposure to water is also a problem for roofing materials. Water can erode your roofing materials, which may result in early roof failure.
Water may also enable the growth of algae, moss and lichen. This vegetation can stain or damage your roofing materials. Standing water may also attract animals or insects who are looking for a drink, and they may damage the roof or the rest of your home. Or, they may simply become a nuisance that impacts the quality of your home and your quality of life in it. For example, mosquitoes may breed in standing pools of water on the roof. This may become a nuisance when you try to enjoy your outdoor space.
Damage from ponding may result in a roof leak. One way it can cause a leak is when the depth of the ponding exceeds the height of the flashing on a roof feature, thereby allowing water to penetrate the structure. In cold climates there is also the possibility that the water will freeze in winter. Freeze/thaw cycling can erode the mineral surface on some roofing materials, such as modified bitumen, which can reduce the life of the roof.
For all of these reasons, ponding may also significantly shorten the lifespan of the roof, so do everything that you can, as a homeowner, to avoid it.
Why does ponding happen, and why does it tend to get worse over time? There are several possible causes of this problem, including:
You will need a professional to help you fix ponding on your flat roof. There are several flat roof ponding solutions that your roofer may discuss with you. Which one is right for your roof will depend on what’s causing the ponding and the specifics of your residential roof system. However, to give you an idea of what might be involved, we’ll discuss some common strategies that might be useful to fix ponding on your flat roof.
Ponding tends to get worse over time, and, if not appropriately addressed, can result in roof leaks, premature failure of the roof, and damage to the rest of your home. A professional roofer should be able to get to the root of your ponding problem, resolve it, and help you understand how you can avoid this problem in the future. If you need help with ponding on your residential flat roof, you can find a local roofer to help through IKO’s Contractor Locator.
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