Cause is most likely lack of proper insulation in the attic .
Result of heat from the home melting snow and then refreezing as ice at the gutter.
(I find myself noting which neighbors need insulation all the time.)
Temperature in the attic should be close to the outside as possible.
think of the air between the roof and top of the insulation as an open umbrella.
I can honestly say I have never written up anything on an ice dam. Leaf dam, yes, ice dam. No.
ditto. 
Mover farther south.
Okay, now we’re really gonna find out who lives and work’s in the North!!!
Bob, although you are correct…sometimes… it is not always the case.
Sometimes it is caused by the weather patterns themselves. And gutters.
In my area, today, you can drive around town and find the same condition on 99.9% of the homes. The homes that do not show this, generally do not have gutters. Also, homes that have been vacant over the winter (heat off) are exhibiting the issue.
So what’s happening???
A month ago, most homes did not have any significant ice damming. What has changed is the weather. We have been having temperature swings anywhere from -10f at night to 35f during the day. During the day, the snow is melting and then refreezing in the gutters. As each day passes, since the ice does not melt as easily as the snow, the ice builds up. When the gutters are full of ice, they overflow, and create the ice dams. The roof exposures to the East and South are exhibiting this much more than West and North facing.
Note: the homes with gutters, that also have leaf guards, are twice as worse as those without guards.
gotta be lamest “Narrative” so far.
The same has been going on here as well. I knocked off some nice 6 foot icicles hanging off my gutters recently. We’ve had a lot of gutters falling off houses around here recently
Not a narrative, but education for those that assume the only cause is as Bob described.
If you look closely at Ben’s pictures, you will see the ice buildup in the gutters, and the snow on the roof is not melted in patches, as is typically the case in heat loss.
When the condition exists as I described, I do not have a narrative. I make note of the condition, and explain verbally to the client the cause. For the stated condition, there is no cure. Except to move South, as others have advised 
I sometimes wonder how many inexperienced inspectors write-up as a defect the withdrawn gutter nails, without understanding that the “glacier” is pulling them out as it travels downward. Should always use screws in the North, not nails.
I have to agree with Jeff. With the temp swings we see at this time of year around here that is pretty common. Heat loss can be a contributing factor but it is not the only cause.
Exactly! Same in my region. Exterior temperature change and solar heat that no attic insulation/ventilation system can prevent.
Especially if the overhang is 16" or more very common on weather conditions regardless of attic insulation. all the more reason to use ice guard on roofs.
For The Record: We observed ice damming on the roof. The potential for ice dams varies with the severity of the winter and depending on insulation and ventilation under the roof. Severe ice dams can result in leaks, typically near the eaves. Solutions include better attic insulation and ventilation, eave protection below the roof coverings, or as a stop-gap measure, the installation of heating cables on the roof.
my narrative…welcome to Ohio…it is winter here…you’re gonna have that…
That is why I said, most likely guys.
You gotta be there to follow up.
And nobody took that away from you.
Sorry, I am just used to defending my position around here.
Oh1 …and on the forum too.
Well, if you wouldn’t keep opening the door… :twisted:
Bob, you have good instincts, but you have to have a reason.
In our area, houses are very drafty (lack of air sealing) and the attic floor is, usually, only blown in insulation.
With no vapor barrier.
And many can lights, not sealed.
WHERE IS THE BUILDING ENVELOPE?
Is it on the ceiling, with the attic venilated (Poorly, badly installed Cobra vents)?
Of is it on the underside of the roof deck? (Better, accounts for air sealing).
The whole roof should (given best practices) melt at the same rate because the whole roof is the same temp.
Hope this helps;