How a Closed Valley Works
A roof valley is the internal angle where two sloping roof planes meet, forming a channel that funnels rainwater and snowmelt off the roof. In a closed valley, the shingles themselves carry the water across that channel rather than an exposed metal liner. There are two common styles:
- Closed-cut valley: Shingles from one plane run through the valley first, then shingles from the second plane are laid over the top and trimmed in a clean line a few inches off the valley center.
- Woven valley: Shingles from both planes are interlaced and woven together across the valley with no cut line.
Underneath, a quality installation still includes a waterproof membrane and often a hidden metal liner for protection. The difference is purely on the surface: a closed valley hides the channel under shingles, while an open valley leaves a visible metal strip down the center.
Why It Matters in the Spokane and Inland Northwest Climate
Valleys are the hardest-working part of any roof because so much water and snow concentrates there. In our region, that channel may handle the runoff from large sections of roof during a fast spring melt or a heavy rain-on-snow event. A closed valley keeps the underlayment fully protected and gives a smooth, continuous shingle surface for water to track across.
The trade-off matters here. Because shingles cover the channel, a closed valley relies on the granular shingle surface to move water and shed snow. Under deep snow loads, freeze-thaw cycles, and ice dams, ice can build up over the shingles and water has fewer places to escape than it would with a wide metal channel. That is why many roofers in cold, snowy climates favor open metal valleys for the snowiest exposures, and why correct underlayment and high-quality shingles are critical when a closed valley is used.
Closed Valley vs. Open Valley
Both styles can perform well when installed correctly, but they have different strengths:
- Closed valley: Cleaner, more uniform look that blends into the roof; lower visible metal; popular for curb appeal.
- Open valley: A visible metal channel that sheds water, ice, and debris quickly and is generally preferred for steep, snow-heavy roofs in the Inland Northwest.
The right choice depends on roof pitch, how much area drains into the valley, and your exposure to snow and ice. A reputable contractor will recommend the detail that best protects your specific roof rather than defaulting to one style. If your valleys are leaking or worn, addressing them is often part of a full roof replacement.
Signs of Valley Trouble
Valleys are a frequent source of leaks, so it pays to know the warning signs:
- Water stains on ceilings or interior walls near the line where two roof sections meet
- Worn, cracked, or lifted shingles along the valley
- Heavy granule loss or bare spots in the valley channel
- Recurring ice buildup or icicles at the bottom of the valley in winter
Because the membrane and any liner are hidden under the shingles in a closed valley, problems are not always obvious from the ground. A professional inspection can confirm whether the valley detail is sound or contributing to a leak. DG Contracting LLC is a GAF Master Elite roofer serving Spokane and North Idaho and offers a 15-25 year workmanship warranty. Request a free estimate or call (509) 209-1894.