Roof valley: definition, types, installation & uses


Roof valley: definition, types, installation & uses

A necessary aspect of any roofing system, the roof valley plays an important role in directing water away from the roof and protecting the structure from potential damage. However, many homeowners may not be familiar with this important feature and its varieties, causing confusion during repair or installation processes. In this article, we will delve into the definition, types, installation methods, and uses of roof valleys to provide a comprehensive understanding of this essential component in roof construction. Whether you are a homeowner planning to install a new roof or a DIY enthusiast looking to learn more about roofing, this article will serve as a valuable resource.

Roof valley

Roof valley

A roof valley, also known as a roof trough or valley gutter, is a V-shaped area where two sections of a roof meet. This is a common feature in pitched or sloping roofs, where the angle between the two roof sections creates a valley.

The purpose of a roof valley is to direct rainwater, snow, and other debris towards the gutter system and away from the roof. It acts as a channel for water runoff, preventing it from pooling and potentially causing damage to the roof. By allowing water to flow towards the gutter, a roof valley helps to maintain the structural integrity of the roof and protects it from water damage.

Roof valleys can be constructed using different materials such as asphalt shingles, metal flashing, or roof tiles. The choice of material depends on the type of roof and the specific requirements of the building. For example, asphalt shingles are commonly used for sloped roofs as they can easily conform to the shape of the valley.

In addition to directing water runoff, roof valleys also play a crucial role in the aesthetic appeal of a building. A well-constructed and well-maintained roof valley can enhance the overall look of a structure. Alternatively, a poorly constructed or damaged roof valley can be a source of leaks and affect the visual appeal of a building.

One of the challenges with roof valleys is the potential for debris accumulation. Leaves, twigs, and other debris can get stuck in the valley, obstructing the flow of water and causing water backup. This can lead to water seeping into the roof and causing damage, as well as creating a suitable environment for mold and mildew growth. Regular maintenance, such as removing debris and ensuring the integrity of the valley, is necessary to prevent such issues.

In the event of damage to a roof valley, timely repairs or replacements are essential to avoid further damage to the roof and the building. It is important to consult a professional roofing contractor to assess the extent of the damage and determine the best course of action to fix it.

In conclusion, a roof valley is an essential component of a pitched roof that serves to protect the building from water damage and enhance its aesthetic appeal. Proper construction, maintenance, and timely repairs are necessary to ensure the effectiveness and longevity of a roof valley.

Types of roof valley

Types of roof valley

A roof valley is a sloped area on a roof where two different sections of the roof meet. It is created when two roof sections intersect at an angle, forming a valley. This is a common feature in residential and commercial structures and plays an important role in directing rainwater from the roof to the gutters.

There are several types of roof valleys that are commonly used in construction, each with its own distinct characteristics and benefits. In this article, we will discuss the three main types of roof valleys – open valley, closed valley, and woven valley.

1. Open Valley:

An open valley, also known as a raised or cut valley, is one of the most traditional and commonly used types of roofing valleys. It is created by leaving a gap between the two roof sections, allowing rainwater to flow freely down the valley and into the gutter. This type of valley is typically used in areas with low rainfall as it provides efficient drainage and does not allow water to accumulate on the roof.

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Open valleys can be further categorized into two types – exposed and unexposed. In an exposed open valley, the metal flashing is visible on the roof, while in an unexposed open valley, the shingles completely cover the metal flashing.

2. Closed Valley:

A closed valley, also known as a cut-in or California valley, is created by overlapping the shingles of each roof section over each other. This type of valley is considered to be more aesthetically pleasing as the metal flashing is concealed beneath the shingles, giving the roof a smoother and more unified appearance.

Closed valleys are commonly used in areas with high rainfall as the overlapping shingles provide better protection against water infiltration. This type of valley also allows for easier maintenance as the shingles can be easily removed and replaced if damaged.

3. Woven Valley:

A woven valley, also known as a weave-in or tar and gravel valley, is created by alternating shingles from each roof section to create a woven pattern. This type of valley is commonly used in areas with high snowfall as the interwoven shingles provide a more durable and water-tight seal.

Woven valleys require more expertise and time to install as the shingles need to be carefully interwoven, making it a more expensive option. However, it is a popular choice for traditional and historical style buildings.

In conclusion, the type of roof valley used in a construction project depends on the climate, budget, and desired aesthetic appeal. Open valleys are commonly used in low rainfall areas, closed valleys in high rainfall areas, and woven valleys in areas with high snowfall. It is important to consult with a roofing professional to determine the best type of valley for your specific project.

Which roof valley type is best?

Which roof valley type is best?

Roof valleys are an important structural element in a building, as they are responsible for channeling rainwater and snowmelt runoff from the roof into gutters or downspouts. There are various types of roof valleys, each with its own advantages and disadvantages. In this article, we will discuss which roof valley type is considered the best for different types of roofs.

1. Closed or Boxed Valley

Closed or boxed valleys are considered to be the most common type of valley used in residential and commercial buildings. They are created by extending the roofing material past the roof edges on both sides of the valley, creating a neat and clean look. Closed valleys are a cost-effective option and provide good protection against leaks and water damage. They also require minimal maintenance, making them a popular choice among homeowners.

2. Open or Cut Valley

Open valleys, also known as cut valleys, are formed by cutting a groove into the roof deck along the valley line. They are then covered with flashing to protect against water infiltration. Open valleys are often preferred for their aesthetic appeal, as they provide a seamless transition between different roof slopes. However, they are more prone to leaks and require regular maintenance to prevent water damage.

3. Woven Valley

A woven valley is a type of roofing valley that integrates multiple layers of shingles on both sides of the valley. The shingles are woven together at the center, creating a double layer of protection against water infiltration. This type of valley is popular for its durability and ability to withstand heavy rainfall. It is also aesthetically pleasing and can be customized to match the design of the roof.

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4. Closed-Cut Valley

Closed-cut valleys are a combination of the closed and open valley types. They have the appearance of a closed valley, but the shingles are cut at the center to allow water to flow freely. This type of valley provides the best of both worlds ā€“ a clean appearance and good protection against water infiltration. However, it requires more craftsmanship during installation, which can make it a more expensive option.

5. Open-Cut Valley

An open-cut valley is similar to a closed-cut valley, but with the shingles cut on both sides of the valley, providing a completely open channel for water flow. This type of valley is best suited for steep-sloped roofs and areas with heavy rainfall. It offers excellent protection against water infiltration and requires minimal maintenance. However, it is not a visually appealing option and may not be suitable for all types of roofs.

In conclusion, the best roof valley type largely depends on the specific needs and preferences of the homeowner and the type of roof. Closed valleys are the most popular due to their cost-effectiveness and low maintenance, while woven valleys are a durable option for areas with heavy rain. It is important to consult with a professional to determine the best valley type for your roof to ensure proper installation and optimal protection against water damage.

How to install roof valley

How to install roof valley

A roof valley is an important component of any roofing system. It is the area where two sloped sections of a roof meet, forming a ā€œVā€ shaped channel. The purpose of a roof valley is to direct rainwater and other debris off the roof and into the gutters. A proper installation of a roof valley is crucial to ensure the longevity and functionality of a roof. Here are the steps to follow for installing a roof valley:

1. Gather all necessary tools and materials: The tools needed for a roof valley installation include a ladder, measuring tape, chalk line, hammer, roofing nails, pry bar, tin snips, and a utility knife. The materials required are roofing shingles, roof underlayment, valley flashing, and roofing cement.

2. Prepare the roof surface: Before installing the valley, the roof surface needs to be clean and smooth. Remove any debris, nails, or old roofing material. Make sure the surface is free of any bumps or uneven areas.

3. Install the roof underlayment: The next step is to install the roof underlayment. This is a layer of waterproof material that provides extra protection against water intrusion. Start at the bottom of the valley and lay the underlayment in a continuous strip, overlapping each layer by at least 6 inches.

4. Measure and cut the valley flashing: Using a measuring tape, measure the length of the valley and add an extra 6 inches to each end. Cut the valley flashing to this length using tin snips. The flashing should be at least 18 inches wide to ensure proper water flow.

5. Install the valley flashing: Start at the bottom of the valley and nail the flashing in place, leaving the extra 6 inches on each end to be folded over later. Use roofing nails to secure the flashing to the roof, placing a nail every 6-12 inches.

6. Install the shingles: Once the flashing is in place, you can begin installing the shingles. Use chalk lines to mark the centerline of the valley on each side. Lay the shingles on each side, starting from the bottom and working your way up. Be sure to overlap the flashing by at least 6 inches.

7. Secure the shingles: Use roofing nails to secure the shingles in place, placing them about 6 inches from the edge and 12 inches apart. Be sure to nail down each tab of the shingles to prevent them from flapping in the wind.

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8. Cut and fold the excess flashing: Once the shingles are installed, cut the extra 6 inches of flashing on each end and fold it over the shingles. Secure it in place with roofing nails and apply roofing cement to seal the edges.

In conclusion, installing a roof valley requires precision and attention to detail. It is important to follow these steps carefully to ensure a strong and functional roof valley that will protect your roof for years to come. If you are not confident in your abilities to install a roof valley, it is best to hire a professional roofing contractor to do the job.

Advantages of roof valley

Roof valleys are the sloping areas of a roof where two roof sections meet. They are typically created by the intersection of two roof ridges or by the intersection of a roof and a dormer or chimney. Roof valleys serve an important purpose in the overall design and function of a roof, and they offer several advantages.

1. Water Drainage: One of the main advantages of a roof valley is its ability to efficiently channel water away from the roof. This is especially important in areas with heavy rainfall and snow. The sloping design of the valley allows water to flow freely towards the gutters, preventing it from pooling and causing damage to the roof.

2. Aesthetics: Roof valleys can add a unique architectural element to a building. They create visual interest and break up the monotony of a single-sloped roof. Additionally, they can be accentuated with decorative metal flashing, adding to the aesthetic appeal of the roof.

3. Improved Ventilation: The intersection of two roof sections in a valley creates a gap that can improve ventilation in the attic space. This allows for better air circulation and helps to prevent moisture buildup in the roof, which can cause mold and mildew growth.

4. Increased Durability: Roof valleys can add structural integrity to a roof. By directing water away from the roof, they prevent water from seeping into the roofing materials and causing rot or other damage. They also help to distribute the weight of the roof evenly, reducing the risk of structural damage from heavy snow or other external factors.

5. Cost-effective: In comparison to other roofing methods, roof valleys are a cost-effective option. They require less material to construct than other types of roofing, making them a more economical choice. Additionally, their efficient water drainage can help prevent costly repairs or replacements in the long run.

6. Accommodates Different Roof Angles: Roof valleys are versatile and can accommodate different roof angles and shapes. This makes them suitable for a variety of roof designs, including gable, hip, and gambrel roofs.

In conclusion, roof valleys offer many advantages that make them an essential component of a well-designed roof. They are not only functional but also aesthetically pleasing and cost-effective. As a civil engineer, it is important to understand the advantages of roof valleys to ensure the proper design and construction of roofs for residential and commercial buildings.


In conclusion, roof valley is an important architectural feature in roofing systems that helps to direct water away from the roof and prevent potential leaks. It is defined as the angled area where two roof slopes meet and can be constructed in different types such as open, closed, or woven. The installation of a roof valley is a precise and crucial process that requires proper planning and skilled workmanship. The uses of roof valley go beyond just water diversion, as it also adds aesthetic appeal to the overall design of a building. Proper maintenance and regular inspection of roof valleys are imperative to ensure their longevity and functionality. Understanding the different types and proper installation techniques of roof valleys can help to enhance the overall functionality and durability of a roofing system.


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