· Michael Blair
Overflow gets blamed on leaves, and leaves are often innocent. Middle Tennessee gets intense short downpours, and a gutter system sized for average rain simply cannot carry them.
Capacity, not blockage
Five-inch K-style gutter with too few downspouts overflows in a heavy Nashville storm regardless of how clean it is. A large roof area feeding a single downspout is the usual cause.
Six-inch gutter carries substantially more, and adding a downspout is often cheaper and more effective than upsizing the whole run.
Pitch and hanger spacing
Gutters need a slight fall toward the downspout, commonly around a quarter inch per ten feet. Too little and water stands; too much and it looks wrong and outruns the outlet.
Hangers spaced too far apart let a full gutter sag between them, which creates a low point that holds water and eventually pulls the gutter away from the fascia.
- Count downspouts against roof area
- Check fall toward the outlet, about a quarter inch per ten feet
- Hangers at roughly two-foot spacing, closer in heavy-rain areas
- Check the drip edge tucks into the gutter, not behind it
- Valleys concentrate water — often need a splash guard
Where the roof meets the gutter
If the drip edge directs water behind the gutter rather than into it, the gutter can be spotless and water still runs down the fascia. It is a common detail error on older roofs.
Valleys are the other one. A valley dumping onto a short gutter run overwhelms it locally, and a splash guard at that point is a small fix for a persistent problem.
What overflow costs
Water running down the wall soaks fascia and siding, and water landing at the foundation is exactly what Middle Tennessee clay does not need.
Overflow at one corner repeatedly is often the reason a driveway or patio corner has settled, and it is worth connecting the two.