How to Keep Roofs Draining Properly

Loss Control Insights

Drains are a humble, hidden feature we all depend on. Sink drains and floor drains take water away from the inside of our businesses, while storm drains keep our parking lots and streets safe from surging and standing water. Equally as important, drains also protect the exterior of our buildings. Drainage systems help move water away from a building’s exterior as quickly as possible so it doesn’t have a chance to seep into any gaps or holes.

Depending on the type of roof the building has, the drainage system may include gutters and downspouts, interior drains and/or scuppers.

  • Gutters and downspouts direct water on roofs away from buildings. This system protects both the building exterior and the foundation, keeping water from running off the roof straight down the side of the building to the foundation.

  • Internal drains run water from the roof into pipes that go through the building. They usually discharge into a storm sewer system.

  • Scuppers are openings at a building’s perimeter that allow water to drain into a downspout. They are usually surrounded by a metal box that acts as flashing and directs water to run through the wall.

Ways Water Can Cause Roof Problems

Since drains, gutters and scuppers must have the capacity to get rid of a large amount of water very quickly, clogging is always a potential problem. Debris—including leaves, branches or ice—can quickly clog drains, especially during a heavy storm.

If water can’t get to the drains or gutters, it will pond on flat roofs. This is a problem, as standing water one-inch deep adds five pounds per square foot of load to the roof, or about 2,000 pounds of extra weight on a 20-by-20 area of roof. Slanted roofs also have problems if water can’t flow through drains or gutters. The result can be foundation or basement problems, due to either water pounding on the ground near the building or ponding close to the foundation.

Standing water can also deteriorate roofing materials, such as membranes and shingles, and it can work its way under flashing and other sealants. A freeze-thaw cycle can cause cracks in many roofing materials, allowing water to seep through to the interior.

Maintain Proper Drainage

Being observant and proactive when it comes to maintenance is important to keep drains flowing.

The Insurance Institute for Business and Home Safety has these basic maintenance tips:

  • Inspect and clean roof drainage systems at least twice a year, ideally in the spring and fall, with additional checks after severe weather

  • Remove impediments to good drainage on the roof, including keeping tree branches away from the roof, making sure leaves don’t clog roof drains, removing debris left from contractors who work on the roof and cleaning out areas around roof-mounted equipment

  • Clean gutters and downspouts thoroughly, including running water through them to be sure they aren’t clogged and checking for sagging, loose connections, or broken or missing fasteners

  • Repair cracks around drains and examine strainers to be sure they are securely in place

  • Fix problems as they arise, such as removing standing water on your roof, in drainage systems, close to your HVAC system or around the building perimeter

  • Keep downspouts funneling water away from the building so water doesn’t pond too close to the building

  • If you are re-roofing, consider replacing gutters, drains and scuppers with new and better versions at the same time, or at the least, get them back in place and make sure they are functioning properly

  • If you are replacing gutters, look at larger ones for greater flow

Lloyd Williamson