When installing a roof, ensuring that shingles overlap correctly in valleys is crucial for maintaining the roof’s integrity and preventing leaks. Valleys are areas where two roof planes meet, and they are particularly vulnerable to water infiltration if not properly shingled. This guide provides a detailed overview of how far shingles should overlap a valley, including different methods, best practices, and considerations for a successful roofing installation.
| Valley Type | Shingle Overlap Requirement |
|---|---|
| Open Valley | Shingles should overlap the metal valley flashing by at least 2 inches from the chalk line |
| Closed-Cut Valley | The top layer of shingles should overlap the bottom layer by approximately 2 inches |
| Woven Valley | Shingles should be pushed snugly into the valley without nailing within six inches of the valley center; specific overlap measurements are not provided but should ensure tight fit to prevent water infiltration |
Understanding Roof Valleys
Types of Roof Valleys
Before diving into the specifics of shingle overlap, it’s important to understand the two main types of roof valleys:
- Open Valley: In this method, the valley is lined with metal flashing, and shingles from both sides of the valley are trimmed back to expose the flashing.
- Closed Valley: In this method, shingles from both sides of the valley overlap and cover the valley completely, creating a continuous shingle surface.
Each type of valley requires a different approach to shingle overlap to ensure proper water runoff and protection against leaks.
Open Valley Method
Installing Metal Flashing
In an open valley, metal flashing is installed along the valley to provide an additional layer of protection against water infiltration. The flashing is typically made of materials such as galvanized steel, aluminum, or copper.
- Flashing Width: The metal flashing should be at least 24 inches wide to ensure adequate coverage.
- Fastening: The flashing is secured to the roof deck using roofing nails or staples, placed at the outer edges to avoid penetrating the center of the valley.
Shingle Overlap
Shingles in an open valley system do not meet at the center of the valley but are trimmed back to expose a portion of the metal flashing.
- Overlap Distance: Shingles should overlap the metal flashing by at least 2 to 3 inches on each side of the valley. This overlap distance ensures that water runs smoothly over the flashing and onto the shingles, preventing water from seeping under the shingles.
- Trimming Shingles: Shingles should be cut in a straight line parallel to the valley centerline. A chalk line can be used to mark the cut line for precision.
Benefits and Considerations
- Durability: The exposed metal flashing provides a durable surface for water runoff, reducing the risk of leaks.
- Aesthetic Appeal: The open valley method can create a distinct visual line along the valley, which some homeowners find aesthetically pleasing.
- Maintenance: Regular inspection of the metal flashing is necessary to ensure it remains intact and free from corrosion.
Closed Valley Method
Types of Closed Valleys
There are two primary types of closed valleys:
- Woven Valley: Shingles from both sides of the valley are interlaced and woven together as they are installed.
- Closed-Cut Valley: Shingles from one side of the valley extend across the valley, while shingles from the other side are cut and laid over the top.
Shingle Overlap for Woven Valley
In a woven valley, shingles from one side are alternated with shingles from the opposite side, creating a continuous, interwoven surface.
- Weaving Technique: Each shingle strip is laid across the valley and woven with the opposing side’s shingles. This method ensures that shingles overlap by the full width of each shingle strip, typically around 12 inches.
- Overlap Distance: The shingles should extend at least 6 inches past the centerline of the valley, ensuring a tight weave that prevents water infiltration.
Shingle Overlap for Closed-Cut Valley
In a closed-cut valley, shingles from one side of the valley are extended over the centerline, and shingles from the other side are cut back to create a clean, straight edge.
- Base Layer: Shingles from the base layer should extend at least 12 inches past the valley centerline.
- Top Layer: Shingles from the top layer are cut back approximately 2 inches from the centerline, overlapping the base layer shingles by at least 10 inches.
Benefits and Considerations
- Seamless Appearance: Closed valleys create a seamless appearance, as the shingles cover the entire valley.
- Weather Resistance: Proper overlap and interweaving ensure that water is directed away from the valley, reducing the risk of leaks.
- Installation Skill: Closed valleys require precise cutting and placement of shingles, which may necessitate professional installation for optimal results.
Best Practices for Shingling Valleys
Using Starter Shingles
Before laying the main shingles, it’s advisable to use starter shingles or a roll of roofing underlayment along the valley. This provides an additional layer of protection and helps guide water away from the valley.
- Starter Shingle Placement: Starter shingles should be placed along the valley, extending at least 6 inches past the centerline on both sides.
Ensuring Proper Nail Placement
Proper nailing is crucial to maintaining the integrity of the shingles in the valley. Nails should be placed away from the valley centerline to avoid creating potential leak points.
- Nail Distance: Nails should be placed at least 6 inches away from the centerline of the valley.
- Nail Sealing: To further prevent leaks, consider using roofing cement to seal the nails, especially in high-risk areas.
Regular Maintenance and Inspection
Regardless of the valley type, regular maintenance and inspection are essential to ensure the longevity and effectiveness of the roofing system.
- Inspection Frequency: Inspect the roof valleys at least twice a year, and after major storms, to check for damage or wear.
- Prompt Repairs: Address any signs of wear, damage, or leaks immediately to prevent further deterioration and costly repairs.
A roof is the upper covering of a building or structure, primarily designed to protect against environmental elements such as rain, snow, sunlight, and wind. It plays a crucial role in maintaining the integrity and comfort of the interior space by providing shelter and insulation.
