What is Ponding?
Water ponding occurs when a flat roof collects water. So how much ponding on a flat roof is acceptable? The National Roofing Contractors Association (NRCA) specifies that water must remain on the roof for between 24 and 48 hours before it is deemed to be ponding. If you have this extra water, you could notice that it gathers near drains or in roof divots.
Why Shouldn’t Flat Roofs have Puddles?
Ponding of any size can seriously harm your roof and house. If the weight of the water is greater than what the building can safely support, it may destroy the construction of the building. Increased weight can put stress on the roof trusses and other sections of the building even if it doesn’t.
The use of roofing materials that are constantly exposed to water is another issue. Your roof’s materials could be eroded by water, which could lead to an early roof failure.
Algae, moss, and lichen can all grow better in water. Your roofing materials may become stained or damaged by this growth. Insects or animals looking for a drink may be drawn to standing water and do harm to your home’s inside or roof. Or else, they might just become a bother that degrades the condition of your house and your quality of life there. For instance, stagnant water on the roof may be a breeding ground for mosquitoes. When you want to enjoy your outdoor environment, this could become an inconvenience.
Ponding damage may cause a roof leak. When the height of the flashing on a roof feature is greater than the depth of the ponding, it might result in a leak that allows water to enter the building. In colder regions, there is also a chance that the water will freeze during the winter. Some roofing materials, such modified bitumen, can have their mineral surface eroded by freeze-thaw cycles, which can shorten the lifespan of the roof.
Ponding may also drastically reduce the roof’s lifespan for all of the aforementioned reasons, so as a homeowner, do everything in your power to prevent it.
Why Does It Happen?
Ponding occurs for unknown reasons, and it progressively gets worse over time. There are a number of potential causes for this issue, including:
- Installation error: A flat roof isn’t completely flat. It needs to be put in place with a little slant to allow for effective roof drainage. Water should be gently directed toward the drains by the slope. You can have ponding at the lowest parts of the roof if the slope is uneven or slopes away from the drains.
- Ponding problems can be caused by slow-moving or clogged flat roof drains. Some flat roofs are so big that siphonic drains are required to transfer water quickly. The intersection of flat and sloped roofs on residential buildings is more frequently a source of trouble. Poor drainage and ponding problems may arise as a result of improper installation of this link.
- Compressed Insulation: Some flat roofs aren’t designed to support people walking on them or storing heavy objects. The insulation may collapse when these roofs are utilized for that purpose. This compression will produce a low area that might inadvertently accumulate water. Over time, the water’s weight may exacerbate this issue. If your flat roof is not specifically built and protected to support large loads, you shouldn’t store items or set heavy decorations there.
- Dips around roof features: Some roof features, such skylights or plumbing vents, can have been built with minor dips that allow water to collect and get worse over time. To avoid this issue, it is crucial to have a skilled roofing professional install these components and their flashing.
- Buildings sink with time, and this settling can occasionally cause issues with the roof’s slope and result water ponding.
- HVAC leaks: When positioned on top of the roof, HVAC equipment can occasionally cause ponding because it is excessively heavy and produces a dip in the roof. Ponding water could potentially be a result of typical condensation or an unusual leak coming from the air conditioner. The equipment replenishes the water even though it may be slowly emptying. You will require an HVAC specialist in this situation to repair the equipment’s leak or reroute the natural condensation.
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