Proper placement, size, quantity, and location are all integral when it comes to overflow scuppers. To recap from Part One, “Overflow Scuppers: Essential Flood Protection for Your Industrial Roof”, scuppers 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 as a back up to ensure water flows off the building instead of accumulating on the roof.
Overflow scuppers are best installed as part of original construction, but can be retrofitted as needed especially when there are modifications to parapet heights. Architects and/or engineers often design and specify the placement due to their expertise in building code requirements, fluid dynamics and plumbing systems. This knowledge is critical when it comes to designing efficient roof drainage systems that can efficiently divert rainwater.
Sizing and Placement of Overflow Scuppers
There are many factors that architects and engineers take into consideration. This includes determining the proper placement, sizing, and height of scuppers based on building needs.
Such considerations include:
- Quantity, Location and Positioning: Proper positioning including calculating the number of scuppers required, where they are to be located and vertical height (usually approximately 3 inches above the top of roof membrane measured along the parapet walls.
- Size and Capacity: Proper sizing ensures the scuppers can handle the expected volume of water. Determining factors include roof area, slope, and climate conditions.
- Integration with Roofing Materials: Scuppers must be compatible with the roofing material in question. They must also be properly sealed to prevent leaks. There are often challenges as scuppers typically get installed through the parapet wall before the entire exterior wall assembly is constructed on new construction projects.
- Compliance with Building Codes: Scupper installation must meet local building codes and Municipal Stormwater Management Guidelines. These standards specify the number, size, and placement of overflow scuppers.
Height, installation, and maintenance of overflow scuppers
We cannot understate achieving the correct height and positioning of overflow scuppers to ensure they function properly. The size of the scupper openings is important. For example, larger openings can handle higher volumes of rainwater, thereby reducing the risk of overflow.
The addition of overflow scuppers on the parapet walls offers sufficient capacity for the drainage system. When roof drains can’t keep up during heavy storms, overflow scuppers take over as an additional emergency path. The vertical placement of overflow scuppers is important. They will not be effective at all if placed too high and will act as extra drain(s) if they are installed too low.
Finally, overflow scuppers must be unobstructed and free of competing structures or design elements to ensure proper water flow. Regular inspections by a professional roofer in Toronto are the best ways to ensure that scuppers and drains remain free and clear of debris.
Alternative overflow scuppers
An alternative type of overflow scupper worth mentioning is an alternative overflow drain (as pictured here). This dual unit has two separate drains: one that takes water from 0, and the other one only after the height of standing water reaches two to three inches high. This second drain takes that excess water to a pipe through the exterior wall, not through the main rain water leader system. These drains are not piped into the same system to account for cases of blockages.
These alternative overflow drains can be installed at low points on the roof. They would not necessarily be positioned along exterior walls.
Interior vs. exterior drainage systems and their failures
Interior and exterior drainage systems have different functions and vulnerabilities, with each one having its own drawbacks and advantages.
- Interior drainage systems feature a collection with strainers or gates over them to keep debris out. The water flows down pipes installed beneath the roof, channeling the water into an underground storm sewer system.
- Exterior systems feature scuppers along roof edges to drain water via downpipes.
Failure of these systems during extreme weather events can lead to significant damage to the foundation. This can also include clogged drains, insufficient capacity, soil erosion, damage to landscaping and poor performance with uneven terrain or high water tables. Your trusted roofer can evaluate the current drainage system and provide suggestions on how to alleviate vulnerabilities.
Having the proper overflow scuppers in place to address these potential drainage system failures is critical for industrial building owners. They serve as a backup system when primary drainage methods fail, and can prevent or mitigate water damage.
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!
