Why drains freeze
A low-slope roof drains through a handful of points: interior drains, scuppers through the parapet, gutters and downspouts. On a sunny winter day, snow melts and runs to them. If a drain sits near a cold perimeter, or the water leaves the building through an exposed scupper or downspout, it can refreeze before it gets away. By the next morning the drain is capped with ice, and the next melt has nowhere to go.
What a blocked drain costs
- Weight. Water weighs about 5.2 pounds per square foot for every inch of depth, on top of the snow already up there.
- Leaks. Ponded water and ice dams back up under flashings and into laps that were never meant to be under water.
- Falling ice. Frozen scuppers and downspouts grow icicles over entrances and walkways, and meltwater that reaches the ground refreezes into slick ice.
Watch the drifts, too
FEMA’s Snow Load Safety Guide points to drifting as a major cause of roof overloads: snow piles up against parapets, rooftop equipment and where a lower roof meets a taller wall. Northern Ohio’s lake-effect snow makes that a real concern. The guide lists warning signs such as sagging roof members, sprinkler heads that drop below the ceiling, creaking or popping sounds, and doors that start to stick. If you see them, get people out and call a design professional.
Snow removal has its own risks: people need fall protection, and shovels and snow blowers can cut a membrane. Plan it before the storm, not during it.
The options
- A drain routine. Clear leaves and debris from drains and strainers in the fall, and check drains after each storm. It costs little and prevents the most common problem.
- Heat at the drains. Electric heat cable in drain bodies, scuppers and downspouts keeps a path open. It needs power on the roof and runs on electricity whenever it is on.
- Automated deicing. Floe, one of the manufacturers we represent, makes a system that uses a liquid deicer instead of heat on the roof. A console with a pump draws from a deicer container and feeds tubing that runs to drains, roof hatches, downspouts and drift-prone areas. Sensors and real-time weather data trigger it when ice is likely. Floe says one system covers up to 500,000 square feet of flat roof, or 20 drains.
- Fix it in the design. At replacement time, tapered insulation and crickets move water to drains faster, and extra drains or overflow scuppers give it more places to go.
Talk it through before winter
Every building is different: where the drains are, how the parapets catch snow, what is below the roof. Call 216-258-3834 to talk about your roof, or see Floe.