10   -  3 inch Ice Melting Pills

Use a roof rake to get most of the snow off
 then toss the ice pucks up on the roof.

Effective to minus 20 F and of course

Harmful if swallowed.

Don't breath in or touch your eyes and keep stored safely.

For Tough areas like 12 inch dams..

cluster these together so they melt and break thru the ice 

and create a channel for water to exit
.

You don't see the results right away, but it does get under the ice dam.
So that the water makes it way thru the gutters and down the spouts.
If it slides off when you toss it up there use a rake to place it up there.

 Specifically formulated for roofs to avoid harmful salts and chemicals, to prevent damage to roofing materials, plants, and pets. 

I put two of these 3 inches from the edge around 3:00pm. By 5:00pm it had melted a 2-3 Foot  section
This has basically solved our ice dam issue as we will use the pills to melt gaps every 5 feet. So our dam is no longer trapping water.