Overflow scuppers play a critical role in building drainage systems. Think of them as water escape routes. It’s important to understand their function, especially in light of climate change and more extreme weather events around the region. These specialized drainage systems prevent flooding by allowing excess water to escape safely. They usually appear on flat roofs of institutional, commercial, office or industrial buildings.
We’ll define overflow scuppers and roof scuppers, their role during storms and floods, and the importance of height and placement. You’ll need a trustworthy, skilled Toronto roofer to evaluate, detail, and install overflow scuppers on your roof. We have found that the need for overflow scuppers is often overlooked by the designers on construction projects.
Overflow scuppers: defined
The main goal of an overflow scupper is a secondary source to drain water off a roof to prevent roof leaks. In other words, they act as a way to relieve pressure on a building if roof drains get plugged, or cannot keep up with the volume of water during a heavy storm.
When the water level rises, the scuppers will kick in to ensure that there’s a way for that water to get off the building instead of accumulating on the roof. They are essentially openings in the wall where a straight flow of water will shoot out to relieve water buildup, either from plugged drain(s) or large storms.Â
This is especially important on roofs where the parapet height is more than three or four inches. Parapets are wall upturns along the edge of a roof. They’re even more important on newer buildings where there’s a positive slope giving you a drop of several inches or more into the roof drains, plus the height of the parapet.
In that case, you could end up with a large amount of ponding water, even with a relatively low parapet wall, before the water goes over the edge of the building. Severe roof leaks are a concern when there is excessive ponding water on a roof.
Why do we need overflow scuppers?
Scuppers will help evacuate the water out through the exterior walls to avoid putting too much strain on the roof. These types of drainage systems, and specified by a mechanical engineer, don’t have a downpipe. There is just an opening in the wall with a straight flow of water.Â
They are placed in walls or parapets on the edge of a roof, about two to four inches above the roof covering. When the primary drainage system is overwhelmed, the overflow scupper becomes the fallback solution.Â
Having several inches of water on a roof poses a lot of stress on the roof assembly. This could result in shorter term costly repairs or damages or longer term structural issues in extreme cases.
By ensuring proper drainage, roof scuppers protect buildings from water damage. Some issues caused by standing water include:
- Roof Deterioration: Roofing materials can deteriorate with prolonged exposure to standing water, resulting in leaks and reduced roof lifespan.
- Mould and Mildew: Accumulating water will encourage mould and mildew growth, posing not only health risks to occupants but unpleasant odours and attracting wildlife (birds, raccoons etc.) as well.
- Structural Damage: Water infiltration weakens the structural integrity of the building over the long term, causing rusting of metal components, wood rot, and damage to interior finishes and insulation.
The role of overflow scuppers in floods and storms
Overflow scuppers form an integral part of storm water management systems. They act as a fail-safe mechanism in case the primary drainage system becomes clogged. This provides an additional outlet for excess water. In turn, this prevents overloading of the roof and potential water intrusion into the interior of the building. This is especially important during heavy rainfall when water volume exceeds the capacity of primary drains.
The importance of roof scuppers cannot be minimized, especially in light of the increasing frequency and severity of floods and storms due to climate change. Indeed, overflow scuppers are essential in handling extreme weather events, including the concept of the so-called “100-year storm”. This is a rainfall event so large that it statistically has only a one-in-a-hundred chance of happening in a given year.
From bad summer storms to hurricanes, property owners are wise to incorporate proper drainage that can save them from shelling out thousands of dollars in lost productivity and repairs.
Elite Roofing has been going back to the buildings affected by these recent major storms. We’ve been evaluating the need to add overflow scuppers complete with heat tracing wires, where practical, to prevent future issues. Such issues can include anything from business shut-down and interior flooding to unexpected repair costs and insurance claims.
Be on the lookout for Part Two of this series, where we discuss the role of architects and engineers in specifying overflow scuppers, as well as height, placement, maintenance and installation guidelines. Â
Contact Elite Roofing today for a quote
Contact us today for a quote and consultation on our roof drainage systems in the Greater Toronto Area to manage flooding concerns. We help building owners and managers ensure their properties are equipped with effective drainage systems that include overflow scuppers. That’s the Elite Advantage.
