Open Valley vs Closed Valley Flashing: Which Is Better?

When two roof slopes meet, they form a valley and that valley handles more water than almost any other part of the roof. Every rainstorm sends water from both sides funneling down through that one channel. Get the valley right and it drains cleanly for decades. Get it wrong and water finds its way under the shingles, into the decking and eventually into the house. One of the biggest decisions in any roof valley is whether to go with open or closed valley construction. And the right answer depends on your roof, your climate and how long you want the valley to last. The choice also determines what kind of roof valley flashing ends up doing the work.

Core Takeaways

• Open valley flashing leaves a strip of metal visible down the center of the valley. It handles high water volume well and tends to last longer.

• The closed valley covers the metal with shingles, so nothing is visible from the ground. It costs less and looks cleaner but durability depends on the shingles.

• Open valleys outperform closed ones in areas with heavy rain or snow. Closed valleys are more common in milder climates where water volume is lower.

• The most common closed valley methods are closed cut and woven, each installed differently with slightly different performance characteristics.

• Most roofing professionals lean toward an open valley for durability but a closed valley remains popular for cost and appearance reasons.

What Is Open Valley Flashing?

Open valley flashing uses a visible metal strip placed along the roof valley. Water flows directly over this exposed metal surface during heavy rain. This method creates a clear path for water without obstruction from shingles.

Metal flashing is fabricated from aluminum, steel or copper. Strength and corrosion resistance differ among these materials. The open valley system performs better in areas with heavy rainfall or snowfall. Debris does not clog because it can be washed away freely.

What Is Closed Valley Flashing?

Closed valley flashing conceals the valley by overlapping shingles. The metal flashing lies beneath the shingles and is not visible from the outside. Wood or other debris tends to build up along the shingle surface, instead of on the exposed metal.

This method creates a seamless look that blends with the rest of the roof. The closed valley system is popular in residential designs where appearance matters. Proper installation is critical because water flows over layered shingles instead of a direct channel.

Open Valley vs Closed Valley Flashing: Key Differences

Choosing between open and closed valleys comes down to understanding how they actually differ across the factors that matter most. Here’s a clear side-by-side comparison.

Advantages and Disadvantages of Open Valley Flashing

Open valleys offer strong performance in many roofing situations. Still, they may not suit every homeowner’s design preference or budget.

Advantages

• Handles high water volume better than closed valleys due to the wide open metal channel.

• Metal flashing outlasts the surrounding shingles so the valley holds up longer without needing attention.

• Easier to inspect during a roof check. Problems show up visually without having to lift shingles.

• Works with almost any roofing material including asphalt shingles, wood shake, tile and slate.

• When something does go wrong it is easier to locate and fix without disturbing the rest of the roof.

Disadvantages

• Costs more upfront in both materials and labor compared to a closed valley.

• A metal strip is visible from the ground which some homeowners find less appealing than a seamless shingle surface.

• Shingle edges along the valley need to be cut cleanly and precisely or they become a weak point where water can sneak in.

• Debris like leaves and twigs can accumulate along the metal edges if not maintained.

Advantages and Disadvantages of Closed Valley Flashing

Closed valleys prioritize appearance while still offering decent protection. The design works best when installed carefully by experienced roofers.

Advantages

• Cleaner look from the ground with no visible metal running down the roofline.

• Lower upfront cost in materials and labor since less flashing is needed and installation is faster.

• Works well in mild climates where water volume is lower and drainage demands are less intense.

• Gives the roof a more uniform appearance which some homeowners and builders prefer aesthetically.

Disadvantages

• Durability is tied directly to the shingles covering the valley. When the shingles go the valley goes with them.

• Debris builds up faster under the shingle overlap creating potential moisture problems over time.

• Harder to inspect during a roof check since problems hide under the shingle surface.

• Not suitable for wood shake, tile or slate roofing materials.

• In heavy rain or high snow areas the shingle overlap can struggle to move water volume efficiently.

• When a leak develops it is harder to locate and fix without removing shingles first.

Roofing Material Compatibility

Not every roofing material works with both valley types and this is where the decision sometimes gets made for you rather than by you.

Asphalt Shingles

Asphalt shingles are flexible enough to work with either method. You can go open or closed on an asphalt shingle roof without any compatibility issues and the choice comes down to the other factors like climate, cost and appearance preference.

Wood Shake

Wood shake is a rigid material that doesn’t bend across a valley the way the woven closed valley method requires. Trying to run wood shake across a closed valley creates gaps and weak points that eventually leak. Open valley is the right call for wood shake roofs and most experienced roofers won’t attempt a closed valley installation with this material.

Tile Roofing

Tile is heavy and completely rigid. Closed valley doesn’t work with tile at all. The tiles can’t overlap across the valley without cracking and the weight creates structural issues at the valley point. An open valley with proper metal flashing is the only practical option for tile roofs.

Slate

Same story as tile. Slate is rigid, heavy and brittle. Attempting a closed valley under slate causes cracking and creates leak points almost immediately. Open valley is standard for slate roofing and any roofer suggesting otherwise should be questioned.

Metal Roofing

The panels in metal roofing overlap and interlock in a way that makes a closed valley impractical in nearly all systems. Open Valley works with metal roofing and provides the drainage function that metal roofs often require, given how quickly water travels across a shiny metal surface.

What Most Roofing Professionals Recommend

Most roofers lean toward open valleys when durability and long-term performance matter most, particularly in areas with harsh weather. Closed valleys remain popular because of cost and appearance and plenty of roofs with closed valleys perform well for years without issue. The recommendation usually comes down to balancing upfront cost against long-term maintenance and the specific demands of your climate and roof design.

Conclusion

Both open and closed valley flashing systems have clear advantages in roofing projects. Open valleys provide better drainage and durability in harsh weather conditions. Closed valleys offer a smoother look that blends with the roof design. The right choice depends on your priorities, climate, and roof structure. Proper installation matters more than the method itself in many cases. A well-installed roof valley flashing system prevents leaks and protects your home for years. Taking time to choose carefully leads to better long-term results.

Read More: 7 Mistakes Homeowners Make When Hiring EPDM Roofing Installers