Valley Flashing for Residential Roofs: A Homeowner's Guide

When two roof slopes meet, the result is a valley—a critical area for water drainage and one of the most leak-prone zones on your roof. That’s why proper valley flashing installation is essential for every residential roofing system in Colorado and Georgia.

Here’s what you need to know.

What Is Valley Flashing?

Valley flashing is a protective metal (usually aluminum, galvanized steel, or copper) installed in roof valleys to direct water safely off the roof. It's a key part of any water management system on pitched roofs.

Why Valley Flashing Matters

• Prevents Leaks: Roof valleys collect more water than almost any other area. Without flashing, water can penetrate the shingles and reach the underlayment or deck.

• Extends Roof Life: Proper drainage reduces wear on your shingles or panels.

• Meets Code & Manufacturer Requirements: Both the IRC and NRCA recommend metal flashing in all roof valleys .

Common Valley Flashing Types

1. Open Valley

   • Exposed metal center with shingles cut back on each side.

   • Best for high water flow areas.

   • Typically installed using W-shaped or V-shaped flashing.

2. Closed-Cut Valley

   • Shingles overlap at the center, covering the flashing.

   • Cleaner appearance, but can trap debris if not maintained.

3. Woven Valley

   • Shingles are interwoven across the valley.

   • Suitable for lower water flow areas but harder to replace.

Best Practices for Valley Flashing Installation

At Roof Nuts, we follow industry-backed standards and best practices including:

• Minimum Width: Use a minimum of 24” wide metal, centered along the valley.

• Underlayment First: Install ice and water shield or high-temp self-adhering underlayment underneath the valley flashing, especially in cold climates like Colorado Springs or Fort Collins.

• No Nail Zones: Fasteners should never be placed within 6” of the centerline of the valley.

• Overlap Joints Properly: At least 6” overlap with sealed joints to prevent capillary action.

Material Choices

• Galvanized Steel: Affordable and strong.

• Aluminum: Lightweight and corrosion-resistant.

• Copper: Long-lasting and ideal for luxury homes.

For metal roofs, we use specialty interlocking flashings that account for panel expansion and contraction.

Local Considerations

In Colorado

Ice dams, snow melt, and heavy runoff demand strong open valley systems with ice barrier membrane. Proper underlayment that extends 2 feet inside the exterior wall line is a must for code compliance .

In Georgia

Intense thunderstorms and high humidity make ventilation and drainage equally critical. We use corrosion-resistant materials like aluminum or coated steel to handle Georgia’s subtropical climate.

FAQs

How do I know if my valley flashing needs to be replaced?

If you see rust, cracks, lifted shingles, or water stains in your attic near a valley—have it inspected.

Can I use roofing cement to fix valley flashing?

Roof cement is a temporary patch at best. Long-term protection requires proper metal flashing replacement.

Is valley flashing required by code?

Yes. Both the International Residential Code (IRC) and most local jurisdictions require flashing at roof valleys.

Final Thoughts

Your roof’s valleys do more work than you might think. That’s why proper flashing isn’t just a detail—it’s a necessity.

If you're replacing your roof or noticing leaks in high-runoff areas, get in touch with Roof Nuts CO or Roof Nuts GA for a full roof inspection. We specialize in code-compliant, long-lasting flashing systems tailored to your climate.

📍 Colorado Residents Call: 303-276-2403
📍 Georgia Residents Call: 404-476-6851
🌐 Visit: https://RoofNutsCO.com | https://RoofNutsGA.com