Drainage problems are common with flat roofs. Ponding, where water pools and remains on the roof for a long time, is one of these problems. Ponding can lead to roof leaks and material degradation, among other problems. Fortunately, you can deal with roof ponding and avoid the associated damages if you diagnose the problem correctly.
Flat roofs need drainage systems to get water off the roof. Examples of such drainage systems include:
- Inner drains that sit just under the roof and are invisible from outside
- Scuppers, which are openings in the side of the wall
- Gutters that collect water from the roof
These systems have one thing in common — they should be clear to allow efficient water flow. Debris, such as dirt, leaves, or twigs, can block the drainage channels and prevent water flow. Serious blockages might cause water to pond on the roof.
The solution is to clear the drain blockages. In fact, drain flushing should be part of your roof maintenance practices. That way, the debris won’t accumulate to the point of causing serious blockages.
Flat roofs are not perfectly flat. Rather, they have a gentle slope to allow water to flow via gravity. Your flat roof should maintain its initial slope and evenness to facilitate water flow. Indentations interfere with roof pitch and allow ponding. Your roof might develop indentions if:
- It experiences frequent foot traffic, which compresses the insulation underneath
- The roof insulation becomes saturated with water and loses its initial shape
- Roof installations, such as HVAC (heating, ventilation, and air conditioning) systems, overload the roof
The first step is to deal with the underlying cause of the indentation. For example, you may need to limit foot traffic on the roof if that is a problem. After that, you should repair the indentions. For example, you may have to replace the damaged insulation with new materials.
Roof water needs to flow into the drainage channels without hindrances. Roof protrusions can block water even before it gets to the drainage channels. Such protrusions can trigger ponding because they divert the water from its natural path. Examples of such protrusions include:
- HVAC units
Roof crickets can help if the diagnosis confirms the protrusions to be the problem. Crickets are ridges that divert water around obstructions and direct the water to the right drainage channels.
Improper Drain Design
In rare cases, you might struggle with roof ponding because your drainage system is inefficient or inadequate. Maybe:
- The drainage channels are narrow
- The drainage channels are few
- The drainage channels don’t have the right slope
Only a roofing contractor should fix inadequate roof drainage. DIY work on the drainage system might cause further problems.
Each roof has a minimum slope that facilitates effective water flow. Extremely low roofs struggle to drain their water and might lead to ponding. For example, most roofing materials work well with a minimum slope of 2:12, which gives a 2-inch step for every foot (12 inches) of run.
You might have to re-pitch your roof if an improper slope is a problem. Roof re-pitching is relatively costly, so you should try other solutions first. For example, additional drainage points might help, depending on the extent of the anomaly. Get a professional inspection of the roof to determine the best solution.
Use a roofing professional to design and install your flat roof to preempt ponding issues. An experienced roofing contractor can also help if you already deal with ponding. Empire Roofing and Restoration has been active in the roofing industry for decades. Contact us for a quote on ponding or any other roof solutions you need.