Gutter overflow, or water running behind the gutter

Usually capacity or pitch. Not debris. The trough may be undersized for the roof area draining into it, have too few or undersized outlets, be pitched poorly over a long run, or receive concentrated flow from a valley.

Almost always drip edge that is missing, too short, or installed so water runs behind the trough instead of into it. It is one of the most common reasons a fascia rots on an otherwise sound roof.

No. Ice dams are caused by heat escaping into the attic melting snow that refreezes at the cold eave. A gutter full of ice is a symptom of the same condition, and removing gutters does not stop dams forming.

Far enough that roof water is not soaking the backfill against the foundation. Extensions, splash blocks, or buried leaders to a graded daylight point all work. Terminating at the foundation is the default that causes wet basements.

It depends heavily on the product and setting. They can genuinely reduce leaf maintenance under trees, but performance under ice and snow varies a great deal and some designs trap ice and complicate winter clearing. Ask how the specific product behaves in ice.

It is worth pricing as an option. Anything that must be removed and reinstalled for the roof work costs less to replace while the roof is open, and drip edge and gutter interaction is much easier to get right in one operation.

Persistent overflow can wet the roof edge, drip edge, and underlying sheathing over time, in addition to the fascia damage it is more commonly associated with, particularly where water runs behind the gutter. Not into it.

Fall leaf drop is a common trigger for blockage-related overflow, but capacity and pitch problems show up in any season with heavy rain, and winter overflow specifically points toward ice. Not debris.

Yes: if a run has only one working outlet and it is blocked, water backs up along the entire length of the trough until it finds the lowest overflow point, which can be far from the actual blockage.

A correctly sized system should handle the rainfall intensity it was designed for. If new gutters overflow noticeably in a storm within normal regional intensity, that points to a sizing, outlet, or pitch issue worth raising with the installer instead of accepting as normal.

Often yes: corner overflow can indicate a miter or joint issue at that specific point, while mid-run overflow more often points to pitch, capacity, or a blockage somewhere along that section. The location is useful diagnostic information to report.

Yes: trees that drop needles, small seed pods, or fine debris can clog gutters faster and more persistently than trees that drop larger leaves easily cleared in a single pass, which affects how often cleaning is actually needed.