What is the difference between roof flashing and a gutter?
What flashing does
Shingles shed water across the open field of the roof, but they cannot seal the places where the roof changes direction or meets something else. Flashing handles those spots:
- Step flashing where a roof slope runs along a sidewall, woven with each course of shingles.
- Counterflashing on chimneys and brick walls, covering the top of the step flashing.
- Valley metal or membrane where two slopes meet.
- Pipe boots and vent flashing around penetrations.
- Drip edge along eaves and rakes.
Failed flashing is behind a large share of roof leaks, often with shingles that look fine.
What a gutter does
A gutter does not keep water out of the roof at all. It manages water after the roof sheds it, so the runoff does not erode soil, splash siding, rot trim or soak the foundation.
Where they meet
At the eave, drip edge or gutter apron flashing carries water off the shingle edge into the gutter. If that piece is missing or too short, water clings to the underside of the roof edge and runs behind the gutter, rotting the fascia. A gutter can also cause flashing problems: when it overflows near a wall, water can be driven against siding at a kickout spot. That is why a kickout flashing, a small diverter where a roof edge dies into a wall, matters near gutters.
Which one is leaking?
Water inside the house usually means flashing or roofing. Water at the eave, on siding or by the foundation usually means gutters. See roof flashing explained and common causes of roof leaks.