Roof valleys are critical for guiding water off the roof, making proper shingles installation in valleys essential. This article explains best practices for laying shingles in roof valleys, covering open and closed-cut valley methods, materials, and common pitfalls. By understanding valley installation, homeowners and contractors can improve roof longevity and minimize leaks while aligning with current building codes and industry standards.
Understanding Roof Valleys
Valleys form where two roof planes meet, creating a channel that carries rain and snow to gutters. Proper valley installation ensures water flow without seepage at joints. There are several valley types, with two common methods used in the United States: open valleys, where metal flashing is visible and continuous, and closed-cut or woven valleys, where shingles are cut or woven to cover the valley. Each method has advantages and is chosen based on roof design, shingle type, and regional climate considerations.
Materials And Tools
Key materials include high-quality asphalt shingles or composite shingles, valley flashing (for open valleys), roofing cement, nails, a utility knife, chalk line, roofing felt, and a pry bar. For closed-cut valleys, the shingle selection should allow clean cuts and a neat fold at the valley edge. Use compatible shingles and flashing to avoid mismatches that could create gaps or leaks. Safety equipment such as harnesses, sturdy ladders, and fall protection are essential during installation.
Preparation And Layout
Proper preparation reduces errors. Clean the roof surface, remove old roofing material if replacing, and ensure the deck is sound. Install a layer of roofing felt or underlayment up to the valley line, extending slightly into the valley to protect against moisture intrusion. Mark the valley centerline with a chalk line for precise shingle alignment. Plan the cutting pattern to ensure clean, straight edges along the valley and avoid thin shingle tails that could crack under wind uplift.
Open Valley Installation
Open valleys use continuous metal flashing aligned down the center of the valley. The steps include laying the flashing first, overlapped at the center to shed water, and then installing shingles to cover the flashing edges. Start at the eave and work upward, aligning shingles on both sides of the valley. Nail shingles along the sides of the valley, ensuring fasteners penetrate the deck and avoid overdriving. Keep the flashing visible to allow water to flow freely. Seal joints with roofing cement only when necessary and avoid excessive cement that could attract heat or damage shingles.
Closed-Cut Valley Installation
Closed-cut valleys minimize visible metal flashing by folding shingles into the valley. Start by installing a starter row that begins a few inches back from the edge, then place shingles on both sides, cutting the central shingles to fit into the valley. The goal is to have the valley be a clean, uninterrupted surface. Use a straight edge and utility knife to create precise valley cuts. Fold and press the cut shingles into place, ensuring there are no gaps along the valley centerline. Nail every other shingle per manufacturer guidance to maintain wind resistance and allow proper water shedding.
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Woven Valley vs. Cut Valley Considerations
Woven valleys weave one sheet of shingles into the other across the valley and are often used with certain shingle profiles. Cut valleys involve precise trimming to create a narrow valley seam. Woven valleys can offer a cleaner appearance but may be more time-consuming and require careful hand placement to avoid sharps or tearing. Cut valleys may be faster but demand accurate cuts and secure sealing at the valley edges. Both techniques require attention to alignment, edge integrity, and proper fastener placement to prevent leaks.
Common Installation Mistakes And How To Avoid Them
- Uneven valley edge: Use a straightedge to keep a straight, evenly recessed valley line; misalignment can create water pockets.
- Insufficient nailing: Follow manufacturer guidelines for nail quantity and placement to resist wind uplift.
- Poor flashing integration: Ensure flashing or concealed edges are properly sealed and not overlapped in a way that traps moisture.
- Inadequate underlayment: Do not skip or skim the underlayment; it provides a secondary moisture barrier and protects plywood from condensation and leaks.
- Cut shingle damage: Avoid tearing or cracking shingles during valley cuts; use sharp blades and proper technique.
Weather And Timing Considerations
Install valleys in dry conditions when possible. Humidity and rain can affect the bonding of shingles and cement, and wind can lift loose edges. If weather shifts, cover exposed sections with temporary protection and resume once dry conditions return. Temperature also affects the flexibility of shingles; very cold weather can make cutting more difficult, while heat can cause shingles to expand. Plan work in daylight hours to monitor alignment effectively.
Inspection, Maintenance, And Longevity
Regular inspections should occur after heavy storms or seasonal changes. Look for lifted shingles, damaged flashing, or gaps at the valley edge. Re-seal or replace damaged components promptly to prevent leaks. Maintenance includes keeping valleys free of debris like pine needles, leaves, and dirt that can impede drainage. If you notice staining or dampness in the attic directly below the valley, inspect for moisture intrusion and address it immediately to protect the roof deck and interior.
Safety And Code Compliance
Follow Occupational Safety and Health Administration (OSHA) guidelines and local building codes for roofing work. Use fall protection equipment, guardrails, and proper ladder safety. Many regions have specific requirements for valley flashing materials and installation methods; verify with local codes or a licensed roofer before starting work. Proper nail spacing, fastener length, and adhesive use should align with the shingle manufacturer’s specifications to maintain warranty coverage.
Choosing The Right Approach For Your Roof
The decision between open or closed-cut valleys depends on roof design, weather patterns, and personal preference. Open valleys provide robust water shedding and visible flashing, whereas closed-cut valleys offer a cleaner appearance and faster installation with careful cutting. For regions with heavy snowfall, ensure valley drainage is unobstructed and consider incorporating snow guards or diverters if local building practices recommend them. Always prioritize a watertight seam and durable materials to maximize roof longevity.