Roof Valley Leaks

What you will see

Stains below an inside corner of the roofline, often after heavy rain or snowmelt.

Likely causes

Most cases trace back to one of these:

• No ice and water shield under the valley
• Shingles cut too short or nailed too close to the center
• Debris dams from leaves
• Worn shingles in the water path

How urgent is it?

Moderate to high during snowmelt and heavy storms.

Repair options

Depending on what the inspection finds:

• Rebuild the valley with ice shield and new shingles
• Install open metal valley
• Clear debris and adjust gutters

When replacement is the smarter call

If valleys and slopes are both worn, rebuild valleys during a full replacement.

What an inspection should check

Valleys handle more runoff than any other part of a roof, so an inspection there needs to look past the surface shingles. A thorough check covers the underlayment, the metal or shingle valley construction, and how water actually flows during a storm. This is one area where a roof inspection should slow down rather than rush.

• Ice and water shield coverage under the valley, confirmed where accessible
• Shingle cut lines and nail placement along both sides of the valley centerline
• Granule loss or thinning shingles in the water path, which wear faster than flat areas
• Debris buildup, moss, or standing leaves that can dam water during heavy rain
• Gutter and downspout capacity at the base of the valley, since undersized gutters push water back under shingles

Temporary fix vs. permanent repair

Clearing debris out of a valley and checking that gutters are not backing up can reduce leaking in the short term, especially before a forecasted storm. But a valley that leaks because of missing ice and water shield or shingles cut too close to the center will keep leaking until that construction is corrected. A permanent repair usually means rebuilding the valley with proper underlayment and either a tight closed-cut valley or an open metal valley, not just patching the surface.

What happens if you wait

A valley problem tends to get worse with volume, not time alone. Each heavy rain or spring snowmelt pushes more water through the same weak point, which can saturate the decking underneath and eventually lead to rot that spreads beyond the valley itself. Waiting through a full freeze-thaw season in Central Illinois, where water can refreeze in small gaps overnight, often turns a simple valley fix into a decking replacement.

What to do today

After the next rain, check whether leaking only happens during heavy or sustained storms, which points to volume overload rather than a small isolated gap. Look at the valley from the ground with binoculars for visible debris, bare spots, or curling shingles. Clear leaves or branches if you can do so safely, and note which side of the roof the valley leak traces back to before calling for an inspection.

Cost drivers to expect

Valley repair costs vary with the scope of the fix, not just the length of the valley. Common factors include:

• Whether the repair is a partial rebuild of the valley or a full re-roof of both adjoining slopes
• Open metal valley versus closed-cut shingle valley, which use different materials and labor
• Condition of the decking underneath once old shingles are pulled back
• Roof pitch and height, which affect access and safety setup

How to describe it to the roofer

Describe which valley is leaking (front, back, or side of the house), whether it leaks in every rain or only heavy storms, and whether you have noticed debris collecting there. If you can see the valley from the ground, mention whether it looks like a closed shingle valley or an open metal one, since that changes what the repair involves.

Central Illinois conditions that stress valleys

Decatur-area storms bring both heavy summer downpours and winter snowmelt, and valleys take the brunt of both. Wind-driven rain can push water sideways into a valley faster than it drains, and refreezing snowmelt can work into small gaps that widen over a winter. Roofs that combine missing or blown-off shingles with a weak valley tend to leak worse and sooner than either problem alone.

Maintenance after the valley is repaired

A rebuilt valley still benefits from periodic attention. Keep gutters clear at the base of the valley so water has somewhere to go once it reaches the eave, and clear leaves or debris from the valley itself after fall storms, since buildup there is one of the easiest problems to prevent. A quick visual check from the ground after major storms, looking for shingle granules collecting in the gutter below the valley, can flag early wear before it becomes a leak again.

Questions worth asking before you approve the repair

Before work begins, it helps to ask:

• Will the valley be rebuilt with new underlayment, or just re-shingled on top?
• Is ice and water shield being added under the valley as part of this repair?
• Will you check the gutters and downspouts at the base of the valley too?
• How will the new valley differ from what is failing now?
• What is the plan if decking underneath turns out to be damaged once opened up?

Seasonal timing for valley repairs

Spring and fall tend to be practical windows for valley work in Central Illinois, after winter snow load has passed and before the heaviest summer storms arrive. Summer repairs are still routine but may compete with storm response scheduling after major weather events. Waiting until the depth of winter to address a known valley leak risks another freeze-thaw cycle working into the same weak point before anyone can get on the roof.

Common questions