Inspecting & Maintaining Roof Drains to Withstand Heavy Rainfall
Those who live in the Northeastern United States are well versed in heavy rain events, especially when it comes to summer storms. The Northeast can experience significant rainfall from thunderstorms, tropical storms, and hurricanes moving up the coast.
“To help cities in this region plan for these types of heavy rain events, the International Plumbing Code (IPC) provides an appendix that reports on the rainfall rates of cities,” said Steven Fisher, Brand Manager for Capital Roof Care (CRC). “This information can then be used to design stormwater drainage systems to handle severe rain.”
The IPC rates for rainfall are based on inches per hour that may fall during a storm of one-hour duration and a 100-year return period. In other words, a storm is so severe and dumps so much rain that it only occurs once in 100 years. For these major cities in Maryland, Pennsylvania, and Delaware, the IPC rates are as follows.
- Philadelphia: 3.1 inches
- Harrisburg: 2.8 inches
- Baltimore: 3.2 inches
- Wilmington: 3.1 inches
By planning for the worst—accumulating this much rain in one hour—these cities should easily be able to accommodate typical rainfall amounts.
IPC goes on to say that “roofs shall be designed for the maximum possible depth of water that will pond thereon, as determined by the relative levels of roof deck and overflow weirs, scuppers, edges, or serviceable drains in combination with the deflected structural elements.” To determine how much water could accumulate on a roof, a facility manager should estimate how much water would collect if all primary drains were blocked. According to IPC, “the maximum possible depth of water on the roof shall include the height of the water required above the inlet of the secondary roof drainage means to achieve the required flow rate of the secondary drainage means to accommodate the design rainfall rate as required by Section 1106.”
No matter what commercial roof type you have, it’s imperative to prevent drainage issues from occurring. To avert drainage problems resulting from heavy summer rainfall, a facility manager should inspect a roof annually and incorporate additional maintenance tips to handle substantial water flow.
Annual Roof Inspection
The first thing a facility manager should do to prevent drainage problems from summer storms is conduct a commercial roof inspection at least once a year. At a minimum, four items should be reviewed during a commercial roof inspection. If you don’t feel qualified to conduct an industrial roof inspection in-house, hire a professional like CRC, who will ensure the following items are evaluated, so your roof drains are prepared to withstand serious rainfall amounts.
Clear Debris and Clean the Drainage System
The first thing that should be done to ensure a roof drain can withstand significant summer rainfall is to conduct a visual inspection. Get up on the rooftop and look around, especially before the rainy season. Over time, tree branches and trash can collect on the roof deck, clogging drains. Remove all debris manually or with a shop vac. Focus on drain covers, scuppers, and surrounding areas. The drains should also be flushed with water. Also, use a hose to ensure water flows freely through downspouts and pipes.
Inspect Roof Drain Components
Next, pay special attention to the roof drains and the components.
“Inspect drain covers and grates to ensure they are intact and securely fastened,” said Fisher. “Check the drain bowls and baskets for cracks, corrosion, or other damage, and repair them if needed. Also, take a look at the strainers or domes to ensure they are not deformed or missing. Lastly, examine the sealants around the drains and look for signs of cracking or deterioration in the sealant and flashing.” Any clogged drains could result in emergency roof repair costs.
Check Downspouts and Internal Drain Lines
The third thing you should do during an annual roof inspection is inspect the downspouts and internal drain lines.
“Ensure the downspouts are clear by using a plumbing snake, if necessary, to break up clogs,” said Fisher. “Then check for leaks or corrosion by inspecting joints and seams in the internal drainage systems. Last, but not least, look for signs of wear, which can present as water stains or rust on exterior walls and ceilings inside the building.”
Assess Roof Slope and Drainage Flow
The final thing that should be reviewed during an annual roof inspection to prevent drainage problems is to look for standing water or discoloration on the roof surface. It’s critical to confirm positive drainage. Pooling water may indicate poor drainage or a clogged system. If you see puddling or slow drainage, you may need to re-pitch the roof or add new drains. Also, check for any sagging sections of the roof, which can obstruct the flow of water and worsen with time.
Roof Drain Maintenance Tips
After ensuring your commercial roof is well maintained through an annual roof inspection, the second thing you should do to prevent roof drainage complications from a summer storm is to incorporate additional maintenance tips. The three maintenance tips that are essential for positive roof drainage include preparing for storm events, documenting and tracking maintenance, and implementing additional precautions.
Preparing for Storm Events
There are a few extra steps you can take to prepare your roof drain for a storm event. The first is helping to guide the water off your commercial roof.
“Commercial facilities with low-slope or flat roofs have to work a little harder to remove water, “said Fisher. “Many commercial buildings have large, flat roofs that use internal drainage systems to remove water on the roof deck.” Internal drainage systems allow for drains to be strategically placed throughout the roof deck, with each drain connecting to piping that runs through the building, funneling the water into the ground or sewer.
Although internal drainage systems have many benefits, there are a few drawbacks. These include:
- Clogged drains can cause the caulk, tar, or roofing cement to deteriorate and roofing seams and structural supports to weaken.
- Leaks inside your facility can rust or rot internal support structures, cause mold to form, and result in emergency roof repair services being needed.
To prevent these problems from arising, experts recommend inspecting a flat roof drain at least once per month.
In addition to internal drains, you can ensure your commercial roofing system is guiding water off the roof properly by confirming it goes towards the drains. This can be accomplished by using tapered insulation, such as GAF EnergyGuard tapered Polyiso insulation, a trusted CRC brand.
The two most popular GAF tapered boards deliver a 1/8-inch or 1/4-inch per foot slope. This slight slope prevents water from standing on a roof and forces it toward a drain, which should be strategically installed at various low points on the roof with crickets and saddles. To help water arrive at the drain line or gutter, tapered crickets are typically installed in corners and between drains to direct the flow of water and alleviate ponding. This water must flow down the roof side of the parapet wall and follow the roof slope to reach the drain.
The last thing you can do to prepare your roof for a severe rain event is to install emergency backups. If you have an emergency overflow system in place, it will be activated when water levels are high. By installing a sump pump that runs on backup power, you can also safeguard against power outages, which could compromise internal drainage inside your facility and/or result in a necessary roof leak repair.
Documenting and Tracking Maintenance
The second thing you can do to prepare your roof for a storm with heavy rainfall is to keep a log of industrial roof assessments, cleanings, and repairs. By keeping track of all commercial roof maintenance programs, you can prevent a problem before it starts and ensure your roof performs as optimally as possible.
If you hire a roofing professional like CRC to develop a roof care service plan, they will keep track of all roof maintenance which includes:
- Organizing roof warranty information
- Keeping track of maintenance requirements
- Assessing the conditions of the roof regularly
- Identifying repair needs
- Documenting all roof maintenance assessments and repair activities.
Implementing Roof Drainage Precautions
The third and final thing you can do to prepare your roof for summer storm events with heavy rain is to follow these tips.
- Inspect your roof after each major storm for new damage or clogs.
- Avoid using chemical cleaners, which may corrode pipes.
- Trim surrounding trees to reduce leaf and branch accumulation on the roof deck.
Conclusion
Significant rainfall from summer storms is a common occurrence in the Northeastern United States. By implementing an industrial roof maintenance plan that is performed at least annually, you can prevent roof drainage problems from occurring. Maintaining commercial roof drains is a small investment, compared to the cost of water intrusion, mold remediation, or emergency roofing services. Regular inspections and maintenance will also extend the life of any industrial roof type and provide peace of mind during summer storms.
By working with a trained roofing professional, who documents and ensures all crucial commercial roof drain system components are functioning optimally, and implementing a few additional roof drain maintenance steps, you can be confident your commercial roof drains will withstand any significant rainfall this summer.
Sources:
https://codes.iccsafe.org/content/IPC2018P5/appendix-b-rates-of-rainfall-for-various-cities
https://resources.hy-techroof.com/blog/how-and-when-to-inspect-a-flat-roof-drain
https://codes.iccsafe.org/content/IPC2018P5/chapter-11-storm-drainage