Rain Diverters: Know Everything before Installing

Written By Adam Paul - Waterproofing Expert

A rain diverter is a simple and effective roofing accessory designed to redirect rainwater away from critical or vulnerable areas of the roof. The main task of a rain diverter is channeling the water runoff path on the roof sideways into a gutter or safe drainage path. The angle of a rain diverter typically ranges between 30° to 45°, but it depends on the slope of the roof and the desired redirection path of the water.

The average length of a standard rain diverter is between 36 inches (91 cm) to 48 inches (122 cm). When installing a rain diverter, you should extend it at least 6 inches beyond the protection area. It helps to protect the area properly. A rain diverter benefits the homeowner and the structure to enhance the roof protection from unnecessary water spreading. But if you do not install it properly, it may cause much water-related damage to the roof.

What Is a Rain Diverter?

A rain diverter is a simple and highly effective roof flashing accessory made of galvanized steel, aluminum, or copper, used to redirect roof water runoff away from vulnerable or high-flow rate areas. Rain diverters are installed on the pitched roofs, and the main task of a rain diverter is channeling the water runoff path on the roof sideways into a gutter or safe drainage path.

Rain diverters are installed above entryways, windows, patios, or areas where gutters are absent or overflow frequently. Rain diverters are very important in heavy rains, light drizzles, and melting snow. They’re especially recommended on low-pitched roofs, metal roofs, or older asphalt shingle roofs where water tends to overshoot the gutters.

The main benefits of a rain diverter include preventing water intrusion, reducing splashback, protecting siding and trim, and minimizing soil erosion around the home’s foundation. It’s especially useful when gutters can’t be installed due to architectural limitations or aesthetic preferences.

How Does a Rain Diverter Work?

A rain diverter works by interrupting the downward flow of water on a sloped roof and guiding it laterally toward a collection point, such as a nearby gutter or downspout. It is typically a bent metal flashing, installed under the shingles and tilted slightly to redirect water sideways.

What Is the Angle of the Rain Diverter?

The angle of a rain diverter typically ranges between 30° to 45°, but it depends on the slope of the roof and the desired redirection path of the water. At Aqviz, we usually install it at a 35° angle, which offers the optimal balance for deflecting water laterally without interfering with the roof’s drainage performance. This incline is just steep enough to overcome the downward force of water flow during moderate to heavy rains.

If the rain diverter angle is too shallow, below 25°, water may not divert effectively and can still drip directly downward, defeating its purpose. On the other hand, if the rain diverter angle exceeds 45°, it may interrupt shingle alignment, cause premature wear, or lift under high wind pressure, leading to possible leaks or material damage.

Read More About: 10 Ways To Stop Roof Leaking

What Is the Length of the Rain Diverter?

The average length of a standard rain diverter is between 36 inches (91 cm) to 48 inches (122 cm). Rain diverters should fit the span of the protection area and it should extend at least 6 inches beyond the protected zone, such as above doorways, garage entries, or bay windows for proper runoff.

If the diverter is too short, it won’t cover the width of the vulnerable area. It allows water to leak at the edges. If it’s too long, especially over 60 inches (152 cm), it can interfere with nearby gutters or flashing systems and may require extra bracing to avoid buckling or detachment due to wind load.

How to Install a Rain Diverter?

You can install a rain diverter by following these 7 steps.

Gather tools: Use a pry bar, roofing nails or screws, roofing sealant, tin snips, hammer, measuring tape, and a rain diverter (metal flashing).
Locate the divert position: Measure and mark the section above the roof area you want to protect.
Lift roof shingles: Gently lift the bottom row of roof shingles where the diverter will sit. Use the pry bar to avoid roof damage.
Cut roof diverter to length: Trim the roof flashing to the correct length with tin snips. Make sure it extends at least 6 inches past each end of the target zone.
Insert roof diverter and secure: Slide the diverter under the lifted shingles, angling it slightly downward toward the drainage side. Nail or screw it into place beneath the shingle layer.
Seal the roof edges: Apply roofing sealant around the nail heads and edges to prevent water penetration.
Press and settle: Press the shingles back down and ensure they overlap the diverter smoothly without bulging.

Expert Tips for Roof Diverter Installation

Always seal the roof diverter with high-quality elastomeric roofing sealant. You should do it especially in freeze-thaw regions.
Use butyl tape instead of nails when installing roof diverters on standing seam metal roofs to avoid leaks and preserve the warranty
Use Kynar-coated aluminum roof diverters for corrosion resistance and last long-lasting solution.
Slide the diverter below the second shingle layer to avoid capillary action for roofs with asphalt shingles

What Are the Advantages of Rain Diverters?

There are 5 major advantages of using a rain diverter on a roof.

Protects entryways and patios from direct water runoff.
Reduces siding and trim rot by controlling water exposure.
Prevents splashback and soil erosion around the foundation.
Improves roof drainage where gutters are absent or ineffective.
Minimizes ice formation and icicles near entrances in snowy climates.

Read More About: How to Waterproof a Concrete Roof?

What Are the Problems of Rain Diverters?

Rain diverters are helpful, but like any roof accessory, they come with potential drawbacks if not properly installed or maintained. At Aqviz, we’ve seen several issues arise over time. Here are the 5 key problems of rain diverters.

Water backup under shingles: If the rain diverter is not sealed properly, diverters can cause water to back up beneath the shingles. It leads to the leaking and rotting of the roof structure. This is especially risky during heavy downpours or snowmelt.
Interference with roof drainage: On steep-slope roofs, diverters can obstruct the natural flow of water, leading to pooling or overflows in unintended areas.
Ice dam formation: In cold climates, diverted water may refreeze along roof edges, forming ice dams that damage roof shingles and gutters.
Incompatibility with gutters: When rain diverters are placed too close to gutters can misalign runoff direction or cause overflow at gutter joints.
Wind uplift risk: Poorly secured longer rain diverters can lift during strong winds. It can damage the roof shingles or flashing and create roof vulnerabilities.