Here is a step-by-step process summary for using a pressure washer to remove an ice dam:

• Identify where the ice dams are.
• Shovel the roof as required to expose the ice dam. We typically shovel the entire side of a roof, not just the lower portions. This usually minimizes the likelihood of ice dams reoccurring for a couple of weeks.
• Begin steaming the ice dam either from a ladder or from the roof, job depending. Cut slots into the ice dam every 12 inches to 18 inches (through the ice dam, down to the roofing material). Next, undercut the ice dam from slot to slot to free the ice from the roof. You will know it’s loose when it drops down about an inch. Finally, throw the ice chunks off the roof while watching out for all hazards below. [Where to stand: Standing directly on an ice dam is a pretty safe and stable place to be, assuming you are also under rope and harness. It’s common to see a technician standing on an ice dam and steaming it off as he works his way back toward the ladder.]