Diagnostics
Water Running Behind the Gutter (Wall Stains): Causes
Last updated: May 23, 2026 · Reading time ~5 min
Vertical water stains on siding below the gutter mean water is running behind the gutter rather than through it. Three causes: (1) drip edge flashing missing or improperly installed, (2) gutter sloped backward (tilted away from house), or (3) gutter back is too low relative to the roof edge. Each requires a different fix.
How water gets behind the gutter
Properly installed gutters have:
- Drip edge flashing — a metal strip under the shingles that directs water into the gutter front, not behind it
- Gutter back lip — tucked under the drip edge
- Slight tilt toward house — so water flows in, not over
Missing any of these = water gets behind.
Diagnosis
Stand below a stained section during rain. Watch closely:
- Water spilling over the front of the gutter? Pitch problem or overflow.
- Water dripping from below the back of the gutter? Drip edge missing/wrong.
- Water visibly running down between gutter and fascia? Gutter back lip not under drip edge.
Fix
Drip edge install requires removing the bottom shingle row, sliding in metal flashing, re-securing shingles. About $4-$8/ft. Often paired with full gutter replacement.
Frequently asked
Will this damage my house?
Yes — long-term it rots fascia and soaks siding/sheathing.
Is drip edge required by code?
It's required by most modern roofing codes (IRC 2015+). Older roofs may not have it.
Can I add drip edge without re-roofing?
Partial drip edge install is possible but tricky. Better paired with re-roof.
Related reading
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