Sagging happens when a gutter loses support or is carrying loads it was not meant to hold. Loose hangers, deteriorated attachment points, heavy debris, standing water, snow and ice, or impact damage can all contribute.
Why sag matters
A sag creates a low point. Water sits there instead of moving to the outlet, which adds weight and can make the alignment problem worse. If the gutter has also pulled from the fascia, the repair should account for the attachment surface—not just force the gutter back into position.
If the issue is already affecting water flow or the gutter is physically damaged, see our gutter repair page.