How to Remove Ice Dams Safely in Hood River, Mt Hood and the Cascade Foothills

Where in Oregon do ice dams actually form?

Most of Oregon does not get ice dams. In Portland, Salem and Eugene the winter is wet rather than cold, and the 36 to 39 freeze-thaw days a year that Multnomah, Clackamas and Marion counties average rarely stack enough snow on a roof for a dam to build. The trouble starts where the snow lingers. Hood River County, taking in the town of Hood River, Parkdale and the north side of Mt Hood, averages 76 inches of snow and 55 freeze-thaw days a year, which is more of both than any other county we work in. Government Camp sits higher still and holds a snowpack for months. Sandy, Estacada, Welches and Rhododendron on the Clackamas County side get 19 inches of snow on average but see far more at elevation, and The Dalles and the rest of Wasco County get 22 inches of dry east-side snow with 48 freeze-thaw days to work on it. The mechanism is the same everywhere. Heat leaking from the house through a poorly insulated or badly ventilated attic warms the roof deck under the snow, the snow melts from the bottom, the water runs down to the eave where the roof is cold because there is no living space below it, and it refreezes. The ridge of ice grows, backs up the water behind it, and that water finds its way under the roof covering and into the wall. On older cabins around Government Camp and Welches and the farmhouses up the Hood River Valley, attic insulation is often thin and ventilation an afterthought, so those roofs dam first.

Should I chip, salt or torch an ice dam off my roof?

No, and this is where most of the damage we get called about was done by the homeowner, not the weather. Chipping at a dam with a hatchet, hammer, ice chisel or the edge of a shovel gouges whatever is under the ice. On an asphalt roof the blows shear the mineral granules off the shingle surface, and once the granules are gone the asphalt underneath weathers fast and the shingle is finished years early. On a painted metal roof the same blows chip and scratch the factory finish. A 70 percent PVDF coating like Alunar is very durable against sun and rain, but it is a paint film on aluminum, and a chisel goes straight through it. The finish warranty does not cover mechanical damage, and a scarred eave on a Government Camp cabin is visible from the road for decades. Rock salt is the second mistake. Sodium chloride does melt ice, but it corrodes galvanized gutters, steel flashing and the zinc coating on fasteners, it stains, and the runoff kills the shrubs and lawn under the eave. Calcium chloride is the right chemistry, and more on that below. The third mistake is heat. Propane torches, weed burners and heat guns applied to an ice dam have set fire to the fascia and the dry attic behind it more than once, and hot water from a hose simply refreezes further down and makes the dam bigger. Leave all of it in the garage.

How do I remove an ice dam from the ground in Hood River or Sandy?

Two methods work, both with your boots on the snow and not on the roof. The first is a roof rake, which is a wide aluminum blade on a telescoping pole that sells at any hardware store from Hood River to Estacada. Stand on the ground, reach up, and pull the snow off the lowest three or four feet of the roof along the eave. That band of snow is the water supply for the dam, and once it is gone the meltwater coming down from the warm part of the roof has nowhere to refreeze in bulk. Rake after every significant storm through the winter and most dams never get established. Keep the blade flat to the roof and do not dig at the surface, because a rake dragged hard across asphalt lifts granules and dragged across metal scratches the paint. Watch for the power service drop where it comes to the house, and do not rake under it. The second method is a calcium chloride sock. Fill a leg of old pantyhose or a tube of nylon mesh with calcium chloride pellets, tie it off, and lay it across the dam so it runs from the snow above the ice down over the eave. It melts a channel through the dam within a few hours and the water behind the ice drains through the trench instead of under the roofing. Use calcium chloride and not rock salt, and use the sock rather than throwing loose pellets, which scatter, clog the gutter and land on the plants. When the thaw comes, rinse the eave and gutter with a hose so no chloride residue sits on the metal. Both methods are fine on asphalt, cedar and metal roofs.

When should I call a roofer instead of doing it myself?

Call when water is coming through the ceiling or running down the inside of a wall, because the damage is happening while you read this. Call when the dam is more than a few inches thick and a sock will take too long, when the roof is two storeys and the eave is out of rake reach, or when the pitch is steep enough that you would need to be on it. A chalet-style roof in Government Camp or a steep gable in Parkdale is not a place for a homeowner with a ladder in January. Ladders set against ice-filled gutters slide, and falls are the injury that actually puts people in the hospital during ice-dam season, far more than the ice itself. Ask for a contractor who removes dams with low-pressure steam. A steamer runs water at roughly the temperature of a hot shower through a wand at low pressure, and it cuts the ice away in blocks without touching the roofing underneath. It is the only removal method that is safe on both asphalt granules and painted aluminum. Check the contractor's license on the Oregon Construction Contractors Board site before they climb on your house; anyone doing roofing work in Oregon for pay needs an active CCB number, and ours is 130826. A pressure washer or a hot-water jet is not the same tool as a steamer, and if the crew arrives with one, send them home.

Why do metal roofs on Mt Hood shed snow before a dam can form?

Ice dams need snow to sit on the roof long enough to melt from below and refreeze at the eave. A smooth aluminum roof at a reasonable pitch does not give it that time. Snow bonds poorly to a slick PVDF finish, and once the sun or the attic warms the underside enough to make a film of water, the whole slab releases and slides. That is why the interlocked aluminum roofs we have on record in Hood River, 13 of them since 1999, and the 12 in The Dalles since 1999, get very few ice-dam calls compared with the asphalt roofs next door. There is nothing for the ice to grip. The four-way interlock between panels also means that if water does back up at the eave for an hour, there is no exposed fastener and no open lap for it to enter, which is a separate reason those roofs stay dry. This is not a free pass. A metal roof over a leaky, under-insulated attic will still melt snow from below, and on a low-slope section, behind a chimney or above an entry the snow can hang on and refreeze. Sliding snow is its own hazard, so a Government Camp cabin needs snow guards above the door and the propane tank. The honest sequence for a mountain house is to seal the attic bypasses, add insulation to current Oregon Residential Specialty Code levels, and ventilate the ridge and soffit, and then choose a roof surface that sheds. Do those in that order and the roof rake stays in the garage most winters.

Common questions