The way shingles are installed in roof valleys affects water shedding, durability, and overall roof longevity. This article explains the best practice for determining which side to shingle first, considering valley type, roofing material, and common installation methods used in American homes.
Preparation And Safety
Before starting, ensure the roof surface is clean, dry, and free of debris. Inspect the valley for any structural issues and repair as needed. Use proper fall protection, especially on steep pitches, and follow local building codes. Gather the necessary materials, including shingles, underlayment, flashing, nails, and an appropriate ladder or scaffold. The goal is to create a consistent, watertight installation from the top edge of the roof downward, minimizing the chance of leaks where valleys intersect other roof planes.
Valley Types And Their Impact On Shingle Order
There are two common valley configurations: open valleys and closed (woven) valleys. Each type influences the sequence of shingle installation.
- Open Valleys: Metals flashing lines the valley center. Shingles are typically cut and laid to overlap the flashing from one side, starting on the higher roof plane and working toward the valley center. This approach helps ensure water sheds cleanly toward the center and into the gutters.
- Closed (Woven) Valleys: Shingles from both sides interlock behind the centerline, requiring careful sequencing to avoid gaps. Start on the side with the steeper pitch or the safer, more accessible eave side and proceed toward the valley, ensuring cuts are tight and sealed.
Understanding the valley type guides the initial shingle placement and helps reduce the risk of leaks or improper overlap.
Step-By-Step Guide: Which Side First
The following approach is widely recommended for residential American roofs using asphalt shingles, though specifics may vary by product and local codes.
- Start From the Higher Roof Plane: Begin with shingles on the plane higher up, above the valley. This provides a clean edge and helps gravity direct water toward the lower roof plane and valley center.
- Lay Backing Underlayment And First Shingle: Install underlayment in the valley area per manufacturer instructions. Place the first shingle so its edge aligns with the valley centerline on the higher plane, angling it toward the valley but not covering the entire flashing edge.
- Transition To The Lower Plane: Continue with shingles on the higher side, ensuring proper overhang at the eave. Once a steady course is established on the higher plane, move to the lower plane and maintain consistent shingle alignment toward the valley.
- Overlap And Flasing Considerations: Ensure shingles on the higher plane overhang the valley flashing slightly, while the lower plane’s shingles align with the flashing and valley edge. This prevents water from seeping underneath and directs it toward the valley.
- Cutting And Sealing At The Valley: For open valleys, trim shingles to fit the valley edge precisely, then seal with roofing cement or manufacturer-recommended products. For closed valleys, follow the product’s weaving or interlocking pattern and maintain consistent nail placement.
In practice, starting on the higher plane creates a natural drip edge and helps avoid stepping on newly laid shingles in the valley, reducing damage risk during installation.
Common Mistakes To Avoid
Several missteps can undermine valley performance. Awareness helps installers prevent leaks and ensure long-term durability.
- Starting On The Wrong Side: Beginning on the lower plane can cause improper coverage at the valley edge and misalignment in the centerline.
- Improper Nailing: Nails should be placed per shingle manufacturer guidelines. Nailing too close to the valley edge or too far from it can cause secureness issues or water intrusion.
- Inconsistent Overhang: Uneven overhang along the valley edge can create a trap for water and debris, increasing leak risk.
- Inadequate Flashing Integration: Failing to integrate flashing with shingle edges can create gaps where water can enter.
Tip: Always follow the specific shingle brand’s installation instructions, as flashing and cut patterns vary between products.
Weather And Substrate Considerations
Weather conditions influence shingle installation order. Install during dry conditions to ensure proper adhesion and seal. Excessive wind or rain can disrupt alignment and expose underlayment. The roof substrate should be sound, with no soft spots or damage. If the valley surface is icy, wet, or unstable, delay work and address safety concerns first.
Tools, Materials, And Best Practices
Having the right toolkit helps achieve a precise, durable valley installation.
- Tools: Utility knife, straightedge, chalk line, pry bar, hammer, roofing sealant, and a competent ladder or scaffold.
- Materials: Asphalt shingles, underlayment, valley flashing, compatible adhesive or sealant, and nails suitable for the roof type and climate.
- Best Practices: Maintain consistent shingle alignment, keep valley centerline clear of debris, and periodically check for gaps or misalignments as work progresses.
Maintenance, Lifespan, And Longevity
Proper initial installation supports long-term valley performance. Regular roof inspections, especially after severe weather, help identify wear or damage early. Look for lifted shingles, compromised flashing, or unusual gaps at the valley edge. Address issues promptly to preserve water shedding efficiency and prevent costly leaks. Routine maintenance, including clearing debris from valley channels, contributes to lasting roof integrity.
Frequently Asked Questions
- Q: Which side should I start shingles in a valley on a two-sided roof?
- A: Start on the higher roof plane and work toward the valley center, ensuring proper overlap with flashing and adherence to product guidelines. This reduces the chance of water intrusion and improves seam integrity.
- Q: Do I need a different approach for open vs closed valleys?
- A: Yes. Open valleys typically emphasize flashing support with downward shingle overlap, while closed valleys require careful weaving and alignment so both sides interlock without gaps.