Water dripping behind your gutters? Causes and fixes for Portland homes

Water dripping behind a gutter means roof runoff is reaching the fascia board before it reaches the gutter. The four usual causes are a missing or short drip edge or gutter apron, a gutter hung too far below the roof edge, shingles that don’t overhang the gutter, and a clogged or badly pitched gutter overflowing at the back. Each one leaves different clues.

It matters more in Portland than in most places because the wet season is long. Portland International Airport averages about 36.9 inches of precipitation a year in the NWS 1991–2020 normals, most of it October through April, so wood behind a dripping gutter can stay damp for months. That is how a small drip turns into rotted fascia and gutter hangers that won’t hold.

Diagnose it

Where the water comes out tells you why

1. Sign 1

   Drips between the gutter and the fascia

   Water runs down behind the gutter’s back edge. Most often a missing apron or drip edge, or a gap left when the gutter was hung low.

2. Sign 2

   Water over the front lip

   A clogged outlet, a downspout that won’t drain, or a gutter too small for the roof above it. This one isn’t a flashing problem.

3. Sign 3

   A wet streak below a corner or seam

   A failed joint. Old sealant cracks, and water tracks along the back of the gutter onto the board.

4. Sign 4

   Drips at one spot only in hard rain

   Water shooting past or behind the gutter where a valley or a long, steep roof plane dumps a lot of it at once.

5. Sign 5

   Peeling paint or soft fascia, no drip seen

   Water has been reaching the wood for a while. Soft wood means repair comes before anything else.

None of these shows up on a dry day. Look during steady rain and note where along the run the water appears. That location narrows the cause faster than anything else.

The roof edge

Drip edge vs. gutter apron: what each one does

Oregon’s residential code requires a drip edge at the eaves and rakes of shingle roofs. Under Oregon Residential Specialty Code section R905.2.8.5, it must extend at least 1/4 inch below the roof sheathing and at least 2 inches back onto the roof deck, with laps of at least 2 inches. The 2021 International Residential Code section adds that underlayment goes over the drip edge along the eaves.

A gutter apron is a related flashing that tucks under the first course of shingles and laps down into the back of the gutter, so water can’t slip between the gutter and the fascia. The Asphalt Roofing Manufacturers Association recommends drip edge with an outward-bent bottom flange so water is kept off the wood. GAF’s technical bulletin on drip edges says shingles should overhang the drip edge by 3/8 to 3/4 inch and, where there’s a gutter, overhang its inside edge so water goes into the gutter and not down the face of the building.

Why Portland homes are prone to it

Re-roofed houses, replaced gutters and long rain seasons

Many older Portland homes have been re-roofed more than once, and gutters are often replaced years apart from the roof. Each time, the relationship between the shingle edge, the flashing and the gutter can shift. A new gutter hung below an old roof edge leaves a gap, and that gap is exactly where runoff goes.

Moss and roof grit add a second problem. They hold water at the shingle edge and pile up at gutter outlets, so even a well-flashed edge can spill behind the gutter once the outlets back up. That is why a drip that appears only under trees, or only in November, is often a cleaning issue first and a flashing issue second.

• Missing apron or drip edge: a gutter apron is slid under the first shingle course and lapped into the gutter. It can often be added without taking the gutter down.

• Gutter hung too low: re-hang it tight under the drip edge at the right pitch toward the outlets.

• Shingles too short: an apron bridges a small gap. Replacing the edge course is roofing work.

• Rotted fascia: replace the soft board first, then re-hang the gutter on solid wood. See fascia and soffit repair.

DIY or professional

What you can check yourself, and what needs a contractor

From the ground you can find where the water appears, check whether downspouts flow, and spot peeling paint. Clearing a one-story gutter on a dry day is reasonable DIY work. Lifting shingles to add an apron, re-hanging a gutter or replacing fascia is roof-edge work for a licensed contractor; in Oregon you can look up any contractor’s license on the Construction Contractors Board search.

All Season Continuous Gutters & Roof Care (Oregon CCB #233705) repairs leaking and low-hung gutters and replaces rotted fascia across the Portland metro. Gutter repair visits start at $295; fascia work is priced by scope after we see it. If the gutters are worn out too, seamless gutter installation lets us set the new gutter at the right height from the start.