How to Stop a Roof Valley from overflowing (Using a Roof Valley Diverter)

Have you ever experienced water overflowing from your roof valley, causing damage to your property? In this guide, we’ll explore how a roof valley diverter can help solve this issue and protect your home from potential water damage.

What causes rainwater to accumulate in roof valleys?

Gutters that are not sloped correctly

Proper gutter slope is essential for effective water drainage. Gutters should be installed with a slight downward slope, typically around 1/4 inch of slope per 10 feet of gutter length.

This slope ensures that water flows toward the downspouts and away from the roof valleys. If the gutters are not sloped correctly or if they have sagged over time, water may collect in certain areas, particularly in the valleys.

This can lead to water seepage into the underlying roofing materials, increasing the risk of leaks and water damage.

To address this issue, it’s important to inspect the gutter slope regularly. If you notice standing water or uneven drainage, it may be necessary to adjust the slope by repositioning the hangers or brackets that secure the gutters to the fascia board.

In some cases, it might be necessary to seek professional assistance to ensure proper gutter slope and prevent water accumulation in the valleys.

Clogged Gutters

Gutters can become clogged over time, especially if they are not regularly cleaned and maintained.

When leaves, twigs, dirt, and other debris accumulate in the gutters, they can obstruct the flow of water.

As a result, water may overflow from the gutters or become trapped, leading to pooling in the valleys.

Regular gutter cleaning is essential to prevent clogs. Ideally, gutters should be cleaned at least twice a year, in the spring and fall.

However, if your property is surrounded by trees, more frequent cleaning may be necessary to keep debris from accumulating rapidly.

Removing the debris manually or using gutter guards can help ensure that water can flow freely through the gutter system, reducing the chances of water accumulation in the valleys.

Excessive debris in the gutters

Even if the gutters are not completely clogged, the presence of excessive debris can disrupt water flow and contribute to water accumulation in roof valleys.

This can happen when debris partially obstructs the flow of water, causing it to slow down or divert from the intended path.

To address this issue, it’s important to inspect gutters regularly and remove any excess debris.

This can be done by using a gutter scoop or a hose to flush out the debris. Additionally, trimming tree branches that overhang the roof can minimize the amount of debris falling into the gutters.

By keeping the gutters clear of excessive debris, you can help maintain proper water flow and prevent water from pooling in the valleys.

Improperly fitted gutters

When gutters are improperly fitted or installed, they may not function optimally, leading to water accumulation in roof valleys.

Improper fitting can occur if the gutters are not securely attached to the fascia board or if they have gaps, loose joints, or inadequate sealing.

As a result, water may leak or overflow from these points, bypassing the intended flow path and pooling in the valleys.

To address this issue, it’s important to ensure that gutters are properly fitted during installation or when making repairs.

This includes securely fastening the gutters to the fascia board, ensuring tight joints and connections, and using appropriate sealants to prevent leaks.

If you suspect that your gutters are not properly fitted, it may be necessary to consult a professional gutter installer or contractor to assess and correct the fitting to prevent water accumulation in the valleys.

Poorly maintained gutters

Regular maintenance is crucial for the proper functioning of gutters. Neglecting gutter maintenance can result in various issues that contribute to water accumulation in roof valleys.

Over time, gutters can accumulate debris, such as leaves, branches, and dirt, which can clog the gutters and hinder water flow.

Also, neglecting gutter maintenance can lead to rust, corrosion, and deterioration of the gutter materials, which can cause leaks or improper water flow.

To prevent water accumulation due to poorly maintained gutters, it’s important to establish a regular maintenance routine.

This includes cleaning the gutters and downspouts at least twice a year or more frequently if needed, inspecting for signs of damage or deterioration, and promptly addressing any issues.

Regular maintenance will help ensure that gutters are free from obstructions, in good condition, and able to effectively channel water away from the roof valleys.

Damaged gutters

Gutters can sustain damage due to various factors, such as harsh weather conditions, falling branches, or accidental impact.

When gutters are damaged, they may develop cracks, holes, or sagging sections that impede proper water flow.

Water can escape from these damaged areas, leading to localized pooling in the valleys and compromising the overall effectiveness of the gutter system.

If you notice any damage to your gutters, it’s essential to address it promptly. Depending on the extent of the damage, repairs or replacements may be necessary.

Small cracks or holes can often be patched using gutter sealant or specialized patches, while more significant damage might require the replacement of sections or the entire gutter system.

By ensuring that damaged gutters are promptly repaired, you can maintain the proper functioning of the gutter system and prevent rainwater from accumulating in the valleys.


During heavy rainstorms, the volume of water that flows from the roof can exceed the capacity of the gutter system to handle it efficiently.

If the intensity of the rainfall surpasses the gutter’s ability to collect and channel the water away, it can result in water overflowing from the gutters and cascading into the valleys.

Rainstorms can also contribute to the accumulation of debris, such as leaves and twigs, which can exacerbate the issue by clogging the gutters and impeding water flow.

To mitigate the impact of rainstorms, it’s important to ensure that your gutter system is designed and installed to accommodate heavy rainfall.

This includes selecting gutters and downspouts that have an appropriate size and capacity for your specific climate and the roof area they are intended to serve.

Regular maintenance, including keeping the gutters clean and free of debris, will also help ensure that they can effectively handle rainstorms and minimize the accumulation of water in the valleys.

Roof leaks

Roof leaks can occur due to various factors, including damaged shingles, cracked flashing, deteriorated sealants, or improper roof installation.

When a roof develops leaks, water can penetrate through the roofing materials and seep into the roof valleys, leading to water accumulation.

This is particularly problematic if the gutters are not effectively directing the water away from these vulnerable areas.

To address roof leaks, it’s crucial to identify and repair the source of the leak promptly.

This might involve inspecting the roof for damaged or missing shingles, examining the flashing around chimneys and vents, and ensuring that all seals are intact.

Repairing the roof leaks will help prevent water from infiltrating the valleys, reducing the risk of water accumulation.

Gutters that are too small

Gutters come in different sizes and capacities to accommodate varying amounts of rainfall.

If your gutters are too small for your roof area or the average rainfall in your region, they may struggle to handle the volume of water effectively.

Insufficient gutter size can lead to water overflowing from the gutters and pooling in the valleys.

To address this issue, it may be necessary to upgrade to larger gutters that can handle a higher volume of water.

Consulting with a professional or gutter specialist can help determine the appropriate size of gutters for your specific needs.

Installing larger gutters will allow for improved water flow and reduce the likelihood of water accumulation in the valleys during rainstorms.

Leaves and debris blocking the downspouts

Downspouts play a critical role in directing water from the gutters to the ground.

However, if leaves, twigs, or other debris accumulate and block the downspouts, water cannot effectively flow through them, causing water to back up and potentially overflow into the valleys.

This issue is especially common during the fall season when leaves tend to clog gutters and downspouts.

To prevent leaves and debris from blocking the downspouts, regular gutter maintenance is crucial.

Cleaning the gutters and downspouts at least twice a year, or more frequently if needed, will help ensure that they are clear of any obstructions.

Installing gutter guards or leaf screens can provide an added layer of protection by preventing debris from entering the gutters and downspouts, minimizing the chances of water accumulation in the valleys.

What is a roof valley diverter and how does it work?

A roof valley diverter, also known as a valley shield or valley splash guard, is a device designed to manage the flow of water in roof valleys.

It is typically made of metal or plastic and is installed along the length of the valley, underneath the roofing material.

The purpose of a roof valley diverter is to redirect water away from the valley and into the adjacent gutters or downspouts.

It works by creating a barrier that diverts water to the sides, preventing it from pooling in the valley and potentially causing water damage or leaks.

The diverter directs the water onto the adjacent roof slopes, where it can flow into the gutters and safely drain away from the roof.

Roof valley diverters are particularly useful in areas prone to heavy rainfall or where roof valleys may be susceptible to water accumulation.

How to install a roof valley diverter

  1. Clear the area: Before installation, clear the area from debris and ensure it is free from any obstacles that may hinder the installation process.
  2. Loosen the shingles: Using a simple pry bar, gently dislodge the nails holding the shingles in place. Start loosening the shingles six rows up and one foot per side of the valley. Take care not to damage the shingles during this process.
  3. Slide the diverter under the shingles: Slide the roof valley diverter under the loosened shingles. The diverter’s bended inside edges should allow for placement without damaging the shingles. Ensure that the diverter runs along the length of the valley.
  4. Position the diverter: Position the diverter in a way that the funnel end directs all water flow into the gutter. Ensure that the diverter is fully engaged with the gutter to ensure proper water drainage. If needed, trim the gutter to ensure the diverter sits flat and even under the shingles.
  5. Cut a triangular notch: Cut out a small triangular notch at the center of the diverter. This will allow water to flow over the unit in one direction only in case there is a problem with the gutter system and water is not draining properly.
  6. Secure the diverter: Use pins made from the scrap aluminum to secure the diverter to the roof. Nail the pins into the roof on both sides of the diverter. Make sure not to nail directly into the unit to preserve its waterproof integrity.
  7. Seal the diverter and gutter: Use roof cement to seal the diverter and gutter. Apply roof cement to the nails and pins as well to prevent any water leakage. Seal the inside of the diverter with roof cement to ensure a watertight seal.
  8. Install a leaf guard net: For added protection against debris, it is recommended to purchase a leaf guard net. Lay the leaf guard over the diverter, ensuring a proper fit depending on the roof line. Check the sides for proper coverage of the leaf guard.
  9. Secure the leaf guard: Secure the leaf guard to the diverter using self-tapping screws. Make sure the leaf guard is firmly attached to prevent it from coming loose.
  10. Final fitting and sealing: Do a final fitting of the diverter and leaf guard to ensure everything is properly aligned. Apply roof cement to seal any gaps or areas where water may potentially leak into the gutter.
  11. Optional: Spray paint the unit (if desired): If you want the diverter to match the roof or gutter color, you can spray paint it accordingly. Choose a color that closely matches the surrounding materials. Custom colors may also be available upon request.
  12. Verify functionality: After installation, verify the functionality of the diverter during the next rainfall or by simulating water flow with a hose. Ensure that water is effectively redirected away from the valley and into the gutter, preventing any overflow or water accumulation.

Tools you’ll need to install a roof valley diverter

  • Pry bar or crowbar: Used to gently dislodge nails and loosen shingles for installation.
  • Hammer or roofing nail gun: Required to secure the diverter in place with nails or fasteners.
  • Measuring tape: Used to measure the length of the roof valley and ensure accurate placement of the diverter.
  • Saw or tin snips: Needed to cut the roof valley diverter to the appropriate length.
  • Safety equipment: Work gloves and goggles are essential for personal protection during the installation process.
  • Ladder: A sturdy ladder is necessary to access the roof safely and perform the installation.
  • Roof cement: Used to seal the diverter, nails, pins, and any gaps to prevent water leakage.
  • Self-tapping screws: If installing a leaf guard net, self-tapping screws are required to secure the guard to the diverter.
  • Spray paint: If desired, spray paint can be used to color the diverter to match the roof or gutter for aesthetic purposes.

Risks of water accumulating on roof valleys

Water accumulating on roof valleys can pose several risks and potential problems:

  • Roof leaks: When water accumulates in roof valleys, it increases the likelihood of leaks. The excess water can seep through cracks, damaged shingles, or gaps in the roofing material, leading to water infiltration into the underlying structure of the roof.
  • Structural damage: Prolonged water accumulation in roof valleys can cause structural damage to the roof. The excess weight of the water can put additional stress on the roof structure, potentially leading to sagging, weakened support, or even collapse in severe cases.
  • Roofing material degradation: Continuous exposure to standing water can degrade roofing materials over time. It can lead to the deterioration of shingles, tiles, or other roofing materials, reducing their effectiveness in protecting the underlying structure.
  • Mold and mildew growth: Moisture buildup in roof valleys creates a favorable environment for mold and mildew growth. These fungi can thrive in damp conditions, potentially spreading to other areas of the roof and even into the interior of the building. Mold and mildew growth not only damages the roof but also poses health risks to occupants.
  • Damage to fascia and soffits: Excessive water accumulation can cause damage to the fascia and soffits, which are the boards that protect the roof edges and provide ventilation. Water seeping into these components can lead to rotting, weakening the structural integrity of the roof.
  • Gutter problems: Roof valleys play a crucial role in channeling water into the gutters. If water accumulates in the valleys, it can overflow and bypass the gutters, resulting in water pouring down the sides of the building. This can lead to soil erosion, foundation issues, and potential water damage to the building’s exterior.
  • Ice dam formation: In colder climates, water accumulation in roof valleys can contribute to the formation of ice dams. When the accumulated water freezes, it creates a barrier that prevents proper water drainage. This ice damming can lead to further roof leaks and damage when the ice thaws.

How do you know if a roof valley diverter is right for you?

  • Roof valley configuration: Evaluate the design and structure of your roof valleys. If you have valleys where water tends to accumulate or pool instead of flowing smoothly into the gutters, a roof valley diverter can be beneficial in redirecting the water and preventing potential issues associated with water accumulation.
  • Water accumulation issues: Consider whether you are experiencing problems with water accumulating in your roof valleys. If you notice water pooling, leaks, or damage in the valleys, a roof valley diverter can help alleviate these issues by redirecting water flow and preventing water from seeping into the underlying structure.
  • Climate and rainfall patterns: Assess the climate and rainfall patterns in your area. If you live in an area with heavy rainfall or where intense storms are common, roof valleys can be prone to water accumulation. Installing a roof valley diverter can effectively manage water flow during such weather events.
  • Roofing material and age: Consider the type and condition of your roofing material. Some roofing materials may be more susceptible to water damage and leaks in roof valleys. If your roof is composed of materials that are prone to issues related to water accumulation, a roof valley diverter can provide an extra layer of protection.
  • Maintenance preference: Evaluate your willingness and ability to perform regular maintenance on your roof and gutters. Roof valley diverters require periodic cleaning and maintenance to ensure proper functionality. If you are willing to maintain and clear debris from the diverter and gutters, a roof valley diverter can be a suitable solution.
  • Professional advice: Consult with a professional roofing contractor or a qualified expert who can assess your specific roofing situation. They can provide insights and recommendations on whether a roof valley diverter is the right solution for your needs, considering the specific characteristics of your roof and the potential benefits it can offer.

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Author: Logan

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