Why is water running behind my gutters?

Last Updated: October 23, 2026

Where the water is getting through

When water runs down the back of a gutter, or drips from under it in a line along the fascia, it has found a gap between the roof and the trough. Gutters of Kent repairs and installs gutters across Kent and South King County, with the work done by licensed and insured contractors, and this symptom is one where the gutter is often the innocent party. The trough can be straight, sealed and clear while water still bypasses it at the roof edge. Fixing it starts with finding which of five paths the water is taking, because each leads to a different scope of gutter repair.

Cause 1: no drip edge or gutter apron, or the wrong one

Water does not simply fall off the end of a shingle. Surface tension makes some of it cling to the underside of the roof edge and run backward toward the house, a little in a drizzle and a lot in steady rain. Roof-edge flashing exists to break that path.

A drip edge is a bent metal strip installed at the eave under the underlayment. Its lower leg should extend down into the gutter, so water clinging to the roof edge is led into the trough rather than onto the fascia. A gutter apron has a longer, flatter flange that slides under the shingles and laps over the back lip of the gutter, which closes a wider gap. The guide to drip edge and gutter apron compares the two in detail.

Problems arise in three ways. The flashing may be missing entirely, as it can be on an older roof that was never fitted with it. It may be too short to reach past the back of the gutter. Or the gutter may have been installed in front of the flashing’s leg rather than behind it, so the drip edge directs water down the face of the fascia instead of into the trough. Where an apron can be slipped under the existing shingles and over the gutter, it is a modest repair. Where the roof edge itself needs new flashing under the underlayment, that is roofing work, which is not offered, so it is coordinated with a roofer.

Cause 2: the gutter is hung too low

A gutter needs to sit close enough below the roof edge that water leaving the shingles lands in it. Hung too low, it leaves a gap that water falls through, especially at the high end of the run, where the gutter sits closest to the roof, and the far end, where pitch has carried it lowest. A run that has been pitched too steeply over a long distance can end up several inches below the roof at its outlet end.

The fix is to re-hang the run at the correct height and fall. On long runs, pitching from the middle toward outlets at both ends keeps both ends close to the roof edge. The gutter slope guide explains how fall and height trade against each other.

Cause 3: the gutter has tipped forward or pulled away

Loose hangers let a gutter rotate forward under the weight of water and debris. As the back edge drops away from the fascia, a gap opens that roof water runs straight into. You can often see daylight between the back of the gutter and the board. This overlaps with sagging: hangers that have backed out, rusted or pulled through soft wood. The guide to why gutters sag covers the mechanism, and sagging gutter repair covers re-hanging. Hidden hangers screwed into sound wood at close spacing resist tipping far better than old spikes driven through the face of the gutter.

Cause 4: overflow over the back edge

A gutter whose outlet is clogged or undersized fills up and spills. If the gutter sits slightly back-tilted, or the front lip is higher than the back, the water spills toward the house instead of out over the front. This looks exactly like water behind the gutter, but the cause is in the trough. Check whether the drips stop once the outlet is cleared or the rain eases. The guide to overflowing gutters sorts out the possible causes of overflow.

Cause 5: roof-to-wall drainage

Where a lower roof runs into a sidewall, such as a porch or garage roof meeting a two-story wall, water runs down the step flashing along the wall and reaches the gutter at its end. Without a kickout flashing, a small diverter at the bottom of that wall, the water can miss the end of the gutter and run down behind it, onto the fascia and into the wall framing. A gutter that stops short of the wall, or an end cap that sits against the siding, makes it worse.

The gutter side of this is the run’s length and end detail: carrying the gutter fully to the wall and fitting the end so the kickout empties into it. The kickout itself is part of the roof and wall flashing, so where it is missing it is coordinated with a roofer or siding contractor. Look for staining or soft siding at the lower corner of the wall where the two roof lines meet.

Why fascia rot keeps the cycle going

Fascia is the trim board along the eave that most gutters hang from. Water behind a gutter soaks it from the top and back, often for months before paint peels or the wood feels soft, because the gutter hides it. Rotted fascia then lets hanger screws loosen, the gutter tips forward, the gap at the back widens and more water gets behind it. That is why fixing water behind a gutter sometimes turns into a fascia job.

The walk-around checks the fascia and drip edge along every roof edge for exactly this reason. Where a house has original wood trim, a long history of drips or peeling paint near the gutter line, the board deserves a close look before any new hangers go in. American Community Survey data show 38.5% of Kent housing units were built before 1980; age is not proof of rot on a given house, but where original trim remains, it has had decades of exposure. Gutter and fascia repair explains how damaged sections are replaced before the gutter goes back up.

Why it matters in Kent’s rainy months

Water behind a gutter is a slow-damage problem, and Kent’s climate gives it plenty of time. NOAA’s 1991 to 2020 normals for the Kent station show an average of 96.7 days a year with at least a tenth of an inch of rain, most of them between October and March. A small bypass that wets the fascia on each of those days does more harm over a winter than one dramatic storm. Late summer, when July and August average under an inch of rain each, is the practical window to correct the roof-edge detail before the wet season starts.

Choosing the right repair

Start by watching during a steady rain and noting where the water appears: along the whole fascia, at one end, at one corner of a wall, or only when the gutter is full. That observation separates a roof-edge flashing gap from a hanging problem or an overflow.

If the gutter is sound and the gap is at the roof edge, an apron or a re-hang at the right height is often all it needs. If the fascia is soft over a long stretch, or the gutters are old and dented, replacing the run with new seamless gutters on repaired fascia can make more sense than patching; the repair vs replacement guide works through that choice. Whatever the repair, a water test confirms that water now goes into the trough and out each downspout. You can Get an Estimate when you want the roof edge looked at, or use the problem checker to sort the symptoms first.